Practical Considerations for Manufacturing High-Strength Ti-IOV -2Fe-3AI Alloy Forgings C.C. Chen Wyman-Gordon Company Worcester, Mass. and R.R. Boyer Boeing Commercial Airplane Company Seattle, Wash.
Good fracture toughness can be achieved in high-strength titanium alloys, with the proper manufacturing procedures. These alloys are likely to see substantial usage in the new generation of commercial airliners under development.
SUMMARY
The manufacturing method for producing high-strength Ti-10V-2Fe-3AI alloy forgings with suitable ductility / toughness combinations has been established. The achievable property combinations at high strengths depend critically on the billet chemistry-homogeneity, the forge heat-treat vartables, and the section thickness of the forgings. The manufacturing capability developed in this program has made this alloy an attractive potential for high-strength forging applications on Boeing's future aircraft. The potential of high-strength titanium alloys to improve the structural efficiency of airframe structural forgings brought about a recent development effort for producing Ti-l0V-2Fe-3Al alloy (hereafter designated as Ti-l0-2-3) forgings at the 1242 MPa (180 ksi) strength level. This program was initiated by the Boeing Company in support of its new airplane programs (Figure 1), and included three large forging suppliers and TMCA, the alloy producer. The use of a titanium alloy at the 1242-1380 MPa (180-200 ksi) strength level would allow significant weight savings in replacing steels used at comparable or slightly higher strengths or if used in place of annealed Ti-6AI-4V. However, at such high strengths, the titanium alloys approach their maximum strength capability for production forgings, and close control of both billet materials and processing variables becomes necessary. Most titanium alloys currently used for high-performance aircraft components are alpha-beta alloys (e.g., Ti-6AI-4V). Because of lack of toughness in the solution-treated-and-aged condition and the relatively poor hardenability, the alpha-beta alloys have historically been used in the annealed condition, and hence the strength capability has not been effectively utilized. However, becau'se of the excellent hardenability and heat-treatability of most metastable beta-titanium alloys, such as Ti-1O-2-3, this family should offer significant improvements in both strength and toughness, with improved property uniformity throughout the forgings. The primary objective of this paper is to present the manufacturing techniques and forging properties for high-strength Ti-l0-2-3 alloy forgings developed by Wyman-Gordon Company. Particular emphasis is made on practical variables and technical considerations necessary to produce high-strength forgings with strength/ ductility !toughness properties suitable for airframe applications. JOURNAL OF METALS • July, 1979
Figure 1. Boeing's 767 Model wide-body 200-passenger medium-range airplane.
The minimum property goals of this program were 1242 MPa (180 ksi) ultimate tensile strength, 5% elongation, 10% reduction of area, and 44 MPa ..;m (40 ksi ..;m:) fracture toughness. Practical limitations for the manufacturing applications are also discussed from both the metallurgical and technological standpoints.
ALLOY CHARACTERISTICS AND BACKGROUND The Ti-lOV-2Fe-3Al alloy is metallurgically a near-beta titanium alloy. Like other near-beta alloys, Ti-lO-2-3 possesses processing advantages over the alpha-beta alloys, such as lower elevated-temperature flow stresses (linked to the lower beta transus), improved 33
Table I: General Physical and Mechanical Properties of Ti-10V-2Fe-3AI Alloys
Property
Value
Tensile modulus of elasticity (room temp.) Density
103-107 X 10' MPa (15-15.5 X 10" psi) 4.65 g/ cm:' (0.168 lbs/ inl) 788-802°C (l450-1475°F) excellent
Beta-transus Tensile strength/ ductility / fracture-toughness relationship High-temperature strength and creep-stability Machinability Hardenability Forgeability
Slightly lower than alpha-beta alloys and higher than metastable beta alloys at the same strength level About 4c;" lower than Ti-8Mo-8V-2Fe-3AI and Ti-13VllCr-3AI, but about 5% higher than Ti-6AI-4V Much lower than most commercial titanium alloys Superior to Ti-6AI-4V, Ti-17, Ti-6AI-6V-2Sn, Ti-8Mo8V -2Fe-3AI, and Ti-6AI-2Sn-4Zr-6Mo Comparable to Ti-6AI-4V, but much lower than Ti-6AI2Sn-4Zr-2Mo and Ti-6AI-2Sn-4Zr-6Mo Superior to Ti-8Mo-8V -2Fe-3AI, and comparable to Ti-6AI-4V and Ti-6AI-6V-2Sn (similar cutting speeds, but greater cutter wear) Better than Ti-6AI-4V and Ti-6AI-6V-2Sn, and comparable to Ti-6AI-2Sn-4Zr-6Mo and Ti-8Mo-8V -2Fe-3AI Much superior to commercially available alpha-beta alloys
reasonable excellent excellent through 102-mm (4-in.) section sizes excellent
formability, increased hardenability, and improved strength/ ductility / toughness relationships. J-3 Some of the general properties of the alloy are compared to other titanium alloys in Table 1. As can be seen, the alloy offers significant advantages over the alpha-beta type titanium alloys in both mechanical and physical properties, with only a slight increase in density over Ti-6AI-4V. In addition, the reduced alloying content compared to other metastable beta alloys (e.g., Ti-8Mo-8V-2Fe-3AI and Ti13V-llCr-3AI) and its improved forgeability should result in lowercost forgings. The forgeability, structure, and properties of Ti-10-2-3 have been extensively studied in the past six years."-' Various experimental airframe forgings, rib-and-web forgings, and pancakes were produced at Wyman-Gordon Company during these development programs!-' The technical emphasis was placed on the influence of forging and heat-treating variables on the end properties. However, these development efforts were limited to forgings produced from small ingot materials - 457-mm (18-in) diameter ingots weighing about 908 kg (2,000 lbs). Based on experience gained in forging Ti-1O-2-3 alloy from small ingots, the following information was generated: 1. Excellent strength/ ductility / toughness relationships were achievable at high strengths. Figure 2 presents the strength/ toughness data obtained at Wyman-Gordon at ultimate strength level ranging from 965 to 1310 MPa (140-190 ksi); the results obtained by Rockwell International6 and the Air Force Material Laboratory' are also included. It can be seen from Figure 2 that excellent strength/toughness properties were achievable for Ti10-2-3 alloy forgings at low, intermediate, and high strength levels. Fracture toughness values exceeding 44 MPa.,;m (40 ksi v'ffi) were attained at strengths exceeding 1242 MPa (180 ksi), with elongations of 6% and greater. At the 1034 MPa (150 ksi) strength level, the fracture toughness is at least as good as Corona-5! another promising new alloy for high-fracture-toughness forgings. Such property combinations achievable with Ti-10-2-3 are superior to those attainable with the present forging alloys such as Ti-6Al-4V, Ti-6AI-6V-2Sn, and Ti-17. 2. Preliminary data indicate that the alloy may be amenable to direct aging following the forging operation. Elimination of the solution treatment could offer several potential advantages: a. the distortion and residual stresses resulting from water quenching can be eliminated; b. low-temperature aging without solution treatment may have a beneficial effect on microstructural uniformity for forgings having both massive and thinner sections; c. the possibility of introducing beta flecks during heat treatment may be eliminated; d. the formation of grain-boundary alpha, which often forms upon recrystallization during the solution treatment, may be avoided. Because of relatively lower content of beta-stabilizing elements, Ti-10-2-3 requires considerably 34
Remarks
shorter aging time compared to other metastable beta-titanium alloys. Ultimate tensile strengths ranging from 965 to 1242 MPa (140 to 180 ksi) have been obtained by direct aging, by varying the' aging temperature. The strengthening mechanism is precipitation of a fine dispersion of alpha. It should be pointed out that solution treatment may be required for tensile strengths greater than 1242 MPa (180 ksi).
KI( 20
40
Ko [1o:5;..rm]
or
60
80
FORGING
STRUCTURAL
1-100
;5');s"~)
t~t~~4) SMAll
1NGOT
MATERIAL
120
100
6
BLOCK FORGING
(10/3)
'\l
(J
0
BLOCK
is
0
~".6l
F~~G
210
!!!! 0
200
190 1300
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'l' j!;
1200
z
1 1 \
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6
180
1
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170
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"'~-_Q_------
,.0
~--~20~--~4~0----~60~--~8~0----~,oon---~12~0----~,.~0--~1~ K,corKQ[MPo"'"J
Figure 2. Strength vs fracture toughness for Ti·10V·2Fe·3AI alloy forgings produced from small-ingot material (457 mm dia.).
JOURNAL OF METALS • July, 1979
3. By exercising suitable control of the various forging steps, attractive tensile properties can be achieved through several processing routes, as illustrated in Figure 3. The processing route selected would be based on other considerations such as fracture toughness. Figure 3 also presents the examples of the forging microstructures developed by three commercial processing routes: a. a+(3 block plus a+(3 finish, b. (3 block plus (3 finish, and c. (3 block plus a+(3 finish.
1. The forging properties produced from large ingot materials could not reproduce the attractive properties of the Ti-l0-2-3 alloy forgings previously generated from small ingots. It was found that both tensile strength and ductility scattered widely for a given forging, and the strength! ductility! fracture-toughness relationships could not be systematically correlated. For exam(40 ksi .Jill) the ple, at a fracture toughness level of 44 MPa ultimate tensile strength varied 1104-1380 MPa (160-200 ksi) with the elongations ranging from 1 to 15%.
PRESENT PROGRAM
2. The results of macro- and micro-structural characterization of the large billets reveals the presence of (3 flecks. A significant difference in iron content at center, midradius, and surface locations of the billet slices was observed by chemical analysis. 3. Specific thermomechanical processing (TMP) conditions may be used to improve the structural uniformity and the mechanical properties of the forgings, adequate when heat-treated to the 1242 MPa (180 ksi) strength level.
The present program was initiated in 1977. The objective was to establish a manufacturing method for producing high-strength Ti-lO-2-3 forgings with properties capable of meeting Boeing's property requirements for the new airplane applications. The technical efforts consisted of: (1) characterizing the chemistry, structure, and properties of the billets, (2) producing forgings with selected and optimized forging and heat-treating practices, and (3) evaluating the mechanical properties and structural characteristics of the forgings. The property reproducibility and process adaptability to production conditions were particularly emphasized. The material used was larger production heats from 711-mm (28-in) ingots. Both closed- and open-die forgings were evaluated. The properties of forgings from the larger ingot materials initially produced by three large forgers and alloy producer did not meet those achieved in the previous studies. The main problem was ingot homogeneity, specifically iron segregation. A fairly substantial effort was then undertaken by Wyman-Gordon to isolate and resolve the problem. This effort pointed out some key practical considerations and illustrated their importance in achieving good property combinations at the high strength level being considered. Refinements in the melting practice were also being carried out at TMCA and have improved the ingot quality; RMI is also preparing to melt an ingot of the alloy. ' Preliminary Result from Large Ingot Materials The initial program efforts involved forging and testing of both block and structural-shape forgings produced from large ingots. The results can be briefly discussed as follows:
rm
Alloy Segregation and Structural Inhomogeneity As mentioned before, the primary problem was iron segregation, on both a macro- and micro-scale. The magnitude of the macrosegregation was sufficient to produce significant changes in the macrostructure, which greatly increased property scatter, and the microsegregation produced (3 flecks, which are known to adversely affect ductility and low-cycle-fatigue properties of titanium-alloy forgings. Note that the control over chemistry uniformity during casting is a difficult task for beta-type alloys which contain high amounts of alloying elements; this control is of particular importance in casting large production-size ingots because large castings may experience a wide range of localized freezing and cooling rates. The extent of the macrosegregation is illustrated in Figure 4; the chemistry specimens were taken at center, midradius, and surface locations. The macrostructure of this particular as-received billet slice is fairly uniform and dark-etching (3 flecks are evident. The center of the billet generally exhibits the highest iron content, and the midradius position the lowest. The largest difference in Fe content observed is 0.5 wt. %. The effect that Fe segregation can pro-
a. a+/l block + a+/l finiSh: 1332 MPa (193 ksi) UTS. 8% 8.
b.
{j
block + fJ finish: 1277 MPa (1 85 ksi) UTS. 6.7% EI.
Figure 4. Ti-10V-2Fe-3AI macro etch section showing variation of Fe content (wt. %) with specimen locations, and appearance of flecks for an as-received 11-ln. (279 mm) ReS billet produced from 28-ln. (711 mm) dia. ingot.
C,.
Ii block + a+fJ finish: 1311 MPa, (l90k~i)UT~.9:5%_~I.
Figure 3. Examples of microstructures for Ti-10V-2Fe-3AI alloy forgings produced from small-Ingot materials.
JOURNAL OF METALS • July, 1979
35
duce on macrostructure and tensile properties is illustrated in Figure 5; here significant influence of specimen location and macrostructure on both tensile strength and ductility for a given billet slice can clearly be seen. Chemical analyses were performed adjacent to the fracture surfaces of the tested specimens, and the results indicate that the changes in macrostructures and ductility were associated with the Fe-rich areas. The severity of f3 flecks was also determined for the billet materials; both the maximum and minimum beta transus (f3t) and the nude fleck temperature were evaluated at surface, midradius, and center locations. The results showed that a total spread in f3t (f3t[max.] - f3t[min.]) as large as 42°C (75°F) has been observed in the large-ingot material; the typical spread in the f3t of small-ingot material has been more like 22°C (40°F). Also, nude flecks with a dimension greater than 0.72 mm X 0.72 mm were observable at a temperature as low as f3t (max.) - 65°F for large ingots; the nude fleck temperatures for small ingots are within f3t (max.) - 20°F. Figure 6 illustrates examples of the microstructures along with the resultant tensile properties for the forgings produced from largeingot materials; the wide range of microstructural and property scatter for the forgings can be ascribed to chemical segregation of the ingot or billet. The results of the chemical analyses using a Kevex microprobe analyzer show that the f3-fleck regions are rich in Fe, as illustrated in Figure 7. Since precise control of the forge and heat-treatment temperatures relative to the f3t is of great importance to manufacturing high-strength forgings, the above observation clearly illustrates the practical problems which may be encountered for large-ingot materials. The appearance of f3 flecks greatly complicates selection of forging or heat-treatment temperatures due to local suppression of the beta transus (f3t), in that solution temperatures revolve around the localized f3t. Forging Parameters As previously illustrated in Figure 2, attractive tensile properties can be achieved through several processing routes. The key has been to select the approach providing the best ductility/toughness combination at the required strength level.
Based on the excessive scatter and propensity for low ductility observed in this part of the program, the early efforts were directed toward a+f3 forging. This seemed a logical approach from a production standpoint, as extensive a+f3 working should result in a refined, uniform beta grain structure and provide more uniform properties throughout the forging with maximum ductility at this high strength level. While beta processing provides maximum toughness, the large beta grain size and microstructure resulting from beta processing generally reduces the ductility, which was marginal from the start. The forging operations were conducted in the a+f3 phase field, at 760°C (1400°F) with about 60% deformation. The results from 25.4, 50.8, and 76.2 mm (1, 2, and 3 in) hand forgings are presented in Table II. The tests were made for the specimens at different locations (surface, midsurface, and center) and with different orientations (longitudinal, long transverse, and short transverse). The blocks have the same forging schedule and were produced during the same forge run, but solution temperatures used varied with forging thickness in order to achieve similar ranges of tensile properties. The first observation from Table II is that excellent strength/ ductility combinations were achievedfor all forgings, but the toughness goal of 44 MPa Fro (40 ksi y'ln) was not met. In addition, the two thinner forgings exhibited better ductility and lower fracture toughness than the 76.2-mm product. Results of macroetched slices indicated a practical forging consideration which must be taken into account. The thinner forgings exhibited severe banding in the center portion of the blocks, an indication of preferential metal flow in the center portion of the blocks due to severe surface die-chill. Microstructural examination revealed that the 25.4 and 50.8 mm forgings had a globular alpha morphology and fine beta grain size, while the 76.2-mm forged block contained more lamellar, transformed alpha and a relatively coarse beta grain size. This microstructure/ property relationship (i.e., globular alpha associated with higher ductility and lower toughness and the lamellar morphology associated with higher toughness and lower ductility) is consistent with that reported by Froes et al." It was then decided to f3-forge, followed by an a+f3 finish operation. The fracture toughness is quite sensitive to the extent of
03=P ---. p p
S: S D
L a. {J block + {J finiSh: 1242 MPa (180 ksi) UTS, 3.0% EI. b. P block + a+{j finish: 1290 MPa (187 ksi) UTS, 4.5% EI.
Aging Temperature 16hr
Specim8fl code
OF
PSDH PSBH
TENSILE PROPERTIES
oc
U.T.S. (ksi) (MPa)
Y.S. (ksi) (MPa)
[Ionl, R.~ % %
950 950
510 510
179.6 193.4
1239 1335
170.4 1176 189.3 1306
6 1
21.3 1.8
PSDL PSBL
925 925
496 496
191.9 196.7
1324 1357
180.7 191.5
5 1.5
13.1 1.6
PTDH PTBH
950 950
510 510
189.0 193.3
1304 1334
180.7 1247 188.1 1298
5 I
16.8 1.8
PTBL PTBH
925 925
496 496
191.1 196.7
1319 1357
181.0 1249 194.6 1343
5 1
14.0 2.0
1247 1321
Figure 5. Ti-10V-2Fe-3AI billet slice showing effect of specimen location and macro-appearance on tensile properties. 36
c. a +fJ block + a+{J finish: 1145 MPa (166 ksi) UTS, 2% EI. d. a+fJ block + a+fJ finish: 1283 MPa (186 ksi) UTS, 9.0% EI.
Figure 6. Examples of microstructures for Ti-10V-2Fe-3AI alloy forgings produced from large-Ingot materials.
JOURNAL OF METALS • July, 1979
Table II: Property Results of a+{:J Forged Blocks (203 mm x 203 mm [8 in. x 8 in.] forgings)
Forging thickness 3 in. (76.2 mm)
2 in. (50.8 mm)
1 in. (25.4 mm)
Room-Temperature Tensile Properties 0.2% Y.S. U.T.S. ksi MPa ksi MPa
Orientation* (Location)**
Ductility El.,% RA,%
K 1C or K Q (ksi
-./iii:)
MParm
182-183 184-186 176-190
1256-1263 1270-1283 1214-1311
191-192 193-194 186-200
1318-1325 1332-1339 1283-1380
9-11 8-9 5-9
32-34 20-30 12-34
36.58 36.26 39.26
40.2 39.9 43.2
range: 182-190
1256-1311
186-200
1283-1380
5-11
12-34
36-39
39-43
181-182 184-192 170-173
1249-1256 1270-1325 1173-1194
190-192 195-202 173-180
1311-1325 1346-1394 1194-1242
8-11 5-8 13-14
27-35 12-27 46-59
32.22 31.88
35.4 35.1
range: 170-192
1173-1325
178-202
1228-1394
5-14
12-59
182-186 176-177
1256-1283 1214-1221
194-196 184-184
1339-1342 1270-1270
5-9 10-13
10-25 36-48
27.32 28.05
30.1 30.9
range: 176-186
1214-1256
184-196
1270-1352
5-13
10-48
27-28
30-31
L (~,MS,C) LT (S,MS,C) ST (S,MS,C)
L (S,MS,C) LT (S,MS,C) ST (S,MS,C)
L (S,MS,C) LT (S,MS,C)
-32
-35
*Code: L = longitudinal, LT = long transverse, ST = short transverse **Code: S = surface, MS = mid-surface, C = center
a+{:J deformation; as the amount of a+{:J work done during the finishing operation increases, the greater the loss of the benefits of the prior beta forging, and the lower the toughness. At about the 1310 MPa (190 ksi) strength level, reducing the amount of deformation during the finish operation from about 40% to 20% increased fracture toughness by about 11 MPa rm (10 ksi -Illi). Some a+{:J finishing is required to attain usable ductility, but it must be limited to about 10-25% maximum to obtain satisfactory toughness.
Spectrum 1 (white ): normal region Spectrum 2 (black): fj·fleck region
Figure 7. SEM microprobe analysis of {:J flecks. Spectrum 2 matches perfectly with Spectrum 1 except for significantly higher Fe peak.
JOURNAL OF METALS • July, 1979
Heat Treatment A triplex heat-treatment approach has been utilized in this program - a double-solution-treatment and aging process. The first solution treatment is conducted fairly close to, but below, the beta transus, followed by a slow cool. Some globular alpha will be nucleated at the solution-treatment temperature, which improves ductility, and a lamellar alpha is precipitated and grows during cooling, which is beneficial to toughness. The second solution-treatment is then normally conducted at temperatures below the first solutiontreatment temperature, followed by a water quench to establish the hardenability. Primary strengthening is then achieved by alpha precipitation during the aging treatment. The toughness is also quite sensitive to the aging temperature; a 14°C increase in aging temperature may increase the toughness by about 5.5 MPa .JID (5 ksi -Illi) at this strength level. Another practical concern for structural-component forgings with various section thicknesses is the variation of solution temperature with section thickness required for producing a forging with the desired properties. The solution temperature before quenching has an important effect on the hardenability of the forgings, and a slight increase in solution temperature is needed as the forging thickness increases. However, the degree of heat loss in air increases as the forging thickness decreases, and this tendency should reduce the problem which may be encountered for the structural-component forgings. In other words, controlled quench delays may be utilized to normalize the relative hardenabilities of thin and thick sections, producing more uniform properties. 37
Table III: TI-10V-2Fe-3AI Heat Transfer During Air Cooling
Furnace Temperature OF °C
Delay time, (sec.)
OF
1 in. (25.4 mm) °C
3 in. (76.2 mm) OF °C
1425
774
10 20 30
1421 1406 1387
772 763 752
1425 1424 1422
774 773 772
1425 1425 1424
774 774 773
1415
768
10 20 30
1411 1396 1378
766 758 748
1415 1414 1412
768 767 766
1415 1415 1414
768 768 767
1400
760
10 20 30
1396 1382 1364
758 750 740
1400 1399 1397
760 759 758
1400 1400 1399
760 760 759
Table TIl illustrates the heat transfer nature of Ti-l0-2-3 alloy forgings during an air cool for the cogged forging geometry used for this evaluation; the solution temperatures selected are 1425°F, 1415°F, and 1400°F. A computer program was used to calculate the temperature change due to delay time; here the values of the start· ing temperature, delay time at temperature, forging geometry, ther· mal conductivity, thermal expansion coefficient, thermal emissivity, specific heat, and alloy density were needed for this evaluation. It can be seen from Table III that the relative temperatures before quenching at various section thicknesses for a given structural·com· ponent forging could be practically controlled by the delay time from the furnace to quench tank. CURRENT STATUS Two new ingots were ordered from TMCA; they were used to further define the chemical homogeneity requirements and the processing parameters for manufacturing the alloy forgings. The two ingots were melted using state·of·the·art technology, but with greater attention to potential segregation problems. Chemical analyses of these ingots indicated that the macrosegregation problem was under control and the material was suitable for high·strength forgings. Additional forgings were then produced by both the Wyman· Gordon Company and ALCOA, Cleveland, to demonstrate the property reproducibility and the process adaptability in large structural· component forgings. The Wyman·Gordon forging was a lower link fitting from the Boeing 747 (Figure 8). This part is currently made from Ti-6AI-4V. The die set has a double cavity, so the parts are made in pairs with a total plan view area of about 3942 cm' (611 in'); 4 double or 8 single forgings were produced. Each single forging was about 1500 mm (59 in) long, a maximum width of about 203 mm (8 in), and a variation in thickness from about 25.4 to 82.5 mm (1-3.25 in). This was an attractive part, as it represents a production structural forgo ing, and has a shape. It also had adequate web thickness variation to demonstrate the applicability of the forging and heat treating conditions developed for production of structural·shape forgings. These forgings were {J blocked and a+{J finished, with about 20%
Figure 8. Conventionally-forged Boeing 747 lower-link fitting made from Ti-10V-2Fe-3AI alloy. 38
Center temperature at various section thickness 2 in. (50.8 mm) OF °C
maximum deformation during the finishing or coining operation. They then received a first solution treatment of 779°C (1435°F)/2 hr./ air cool, a second solution treatment of 774°C (1425°F) I 2 hr./ water quench, followed by a 51(jOC (950°F)/8 hr. age. The tensile and fracture properties obtained from these forgings exceeded the program goals. The tensile strength in both heats of material in all orientations ranged 1242-1344 MPa (180-195 ksi), with a minimum elongation of 4%. The fracture toughness was about 55 MPa ~m (50 ksi ~m). A comprehensive evaluation of fatiglle, crack·growth rate, stress corrosion, compression, shear, and bear· ing properties is presently underway. FUTURE CONSIDERATIONS Although isothermal forging of titanium alloys has major advan· tages in better utilization of costly input material, substantial reduction of machining cost, and reduced number of forging opera· tions, substantial cost savings for the isothermal forging of alpha· beta titanium alloys using current technology has never been satis· factorily demonstrated over a wide range of structural·component forgings. IO - 12 The alpha.beta alloys are generally forged at relatively high temperatures (~1750°F or 954°C), and the major obstacle to cost·reduction of isothermal forging has been the high cost of the die materials, tooling, and processing. However, it has recently been demonstrated that, at the present state of technology, isother· mal forging may be regarded as a much more readily acceptable manufacturing process for beta-titanium alloys from both economic and technological standpoints. I' Isothermal forging of alloys such as Ti-1O-2-3 has two key advan· tages over alpha-beta titanium alloys such as Ti-6AI-4V, namely forging temperature and lubricants. Due to the relatively low beta transus and associated excellent forgeability at lower temperatures, lower·cost die materials can be utilized, heat·up times are reduced, and energy consumption is decreased. The forge ability of Ti-l0V· 2Fe-3Al alloy under hot·die conditions at forge I die temperatures or 8431 760°C (1550/ 1400°F) is comparable to that of Ti-6AI-4V at forge I die temperatures of 954/900°C (175011650°F). In addition, recent work at Wyman·Gordon" has demonstrated that lubricants with excellent combination of lubricity, adhesion characteristics, and environmental inertness are available for iso· thermal forging of Ti-l0-2-3. Suitable, reliable lubricants have not yet been developed for the higher isothermal forging temperatures required for the alpha· beta alloys. These considerations, coupled with ever· increasing raw·material costs and material·availability problems could be keys to usage of alloys of this type which can be isothermally forged to lower buyto-fly ratios. CQNCLUSIONS This effort has demonstrated the suitability of Ti-l0V-2Fe-3Al alloy forgings for structural applications at the 1242 MPa (180 ksi) tensile·strength level. Excellent fracture toughness and acceptable ductility can be achieved for large production forgings at this strength level. In addition, the alloy exhibits excellent forging characteristics. JOURNAL OF METALS • July, 1979
Attainment of satisfactory property combinations requires close control of ingot-melting procedures, forging parameters, and heattreatment conditions. This program has demonstrated that suitable control of these parameters can be attained in a production environment using state-of-the-art technology. From a production standpoint, achievement of the property combinations at high strength is strongly dependent on the forging and heat-treating variables, and is limited by the section thickness of the forgings. Specific variables needed to be considered during processing include potential ,B-fleck problems, ,Bt temperature, forging sequence, solution-and-age conditions, and section thickness of the forgings. The fracture toughness of the forgings at the high strength levels can be improved by reducing the degree of a+,B finish and/or by increasing the aging temperature, without significantly sacrificing the strength and ductility. References 1. "Metallurgical and Mechanical Properties of an Advanced High Toughness Alloy TilOV-2Fe-3Al," TIMET Titanium Data (developmental), Titanium Metals Corporation of America, Pittsburgh, Pa., 1976. 2. E. Bohanek, "Deep Hardenable Titanium Alloys for Large Airframe Elements," pp. 1983-2008 in Titanium Science and Technology, Volume 3; Plenum Press: New York, 1973.3. C. C. Chen and C. P. Gure, "Forgeability, Structures, and Properties of Hot-Die Processed Ti-10V-2Fe-3Al Thin Section Forgings," Report RD-74-120, Wyman-Gordon Co., North Grafton, Mass., Nov. 1974. 4. C. C. Chen, "On the Forgeability of Hot-Die Processed Ti-IOV -2Fe-3AI Rib and Web Forgings," Report RD-75-118, Wyman-Gordon Co., North Grafton, Mass., Nov. 1975. 5. E. Bohanek, "Potential of Ti-lOV-2Fe-3AI for Heavy Section Applications," Titanium Metals Corporation of America, Technical Report Number 55 (Project 49-5), May 1972. 6. Private Communication: J. Melill, Rockwell International, and J. Lynch, Schultz Steel, 1974. 7. Private Communication: A. M. Adair, ,Air Force Materials Laboratory, Wright-Patterson Air Force Base, Nov. 1975. 8. R. G. Berryman, J. C. Chesnutt, and F. H. Froes, "A New Cost-Effective Titanium Alloy with High Fracture Toughness," Metal Progress, 112 (8) (1977) pp. 40-45. 9. F. H. Eroes, J. C. Chesnutt, C. G. Rhodes, and J. C. Williams, "Relationship of Fracture on Toughness and Ductility to Fractographic Features in Advanced Deep Hardenable Titanium Alloys," pp. 115-153 in Toughness and Fracture Behavior, STP 651, American Society for Testing and Materials, Philadelphia, Pa., 1978. 10. C. C. Chen et ai, "Advanced Isothermal Forging, Lubrication, and Tooling Process," Air Force Technical Report, AFML-TR-77-136, Oct. 1977.
Campus Newsletter (cant. from pg. 16)
added to his annual salary. The citation was made for excellence in classroom teaching, for recruitment of metallurgy students, including securing of scholarships and support for students, for advising and counseling, and for excellence in relations with alumni of the department. Youngstown State University Dr. Shaffiq Ahmed, Professor of Metallurgical Engineering and Materials Science at Youngstown State University, has been awarded the Western Electric Fund Award of 1979 by the American Society of Engineering Education in recognition of his excellence in teaching and innovations in engineering education.
11. K. M. Kulkarni et ai, "Isothermal Forging of Titanium Alloy Bulkheads," Air Force Technical Report, AFML-TR-74-138, Aug. 1974. 12. A. J. Vazquez and A. F. Hayes, "Isothermal Forging of Reliable Structural Forgings," Air Force Technical Report, AFML-TR-74-123, June 1974. 13. C. C. Chen, "Evaluation of Lubrication Systems for Isothermal Forging of Alpha-Beta and Beta Titanium Alloys," Air Force Technical Report, AFML-TR-77-181, Nov. 1977.
ABOUT THE AUTHORS
C. C. Chen is currently Group Leader in the Research and Development Department of Wyman-Gordon Company, responsible for isothermal forging, titanium alloy studies, and other metallurgical-related problems. He received his MS and PhD degrees in Metallurgical Engineering from Michigan Technological University. Since joining Wyman-Gordon in 1974, he has been concerned with various aspects of forging technology ranging from proceSSing to structure/ property relationships of various alloys, particularly in Ti-base and Ni-base alloy forgings. He has served as program manager and/ or project engineer for several government and industrial contracts in the areas of titanium alloy technology, and is author or coauthor of more than 50 technical papers and reports in the areas of physical metallurgy and metallurgical engineering. Rodney R. Boyer is a research engineer at the Boeing Commercial Airplane Company. He received BS and MS degrees at the University of Washington. He has worked at the Boeing Company for 14 years, the last 11 of which were primarily in the area of titanium technology. He has authored or coauthored more than 30 papers and presentations, most of them in the area of titanium metallurgy.
Advanced Degrees Awarded by Penn State Pennsylvania State University granted advanced degrees during 1978 to the students listed below. There theses titles follow: Metallurgy - Yoon Sam Kim, PhD, Preferential Removal of Co from Co-Pt Alloy by HCI at 700 to 1000°C; Gerald Edward Williams, MS, The Effects of Strain Rate and Grain Size on Strain-Enhanced Dissolution of Zinc from AlphaBrass; John Edwin Allison, Jr., MS, Liquidus of the System Lead Oxide-I ron Oxide-Silicon Dioxide; B. N. Pramila Bai, MS, Orientation Effects in the Erosion of Semi-Brittle Crystals. Mineral Engineering Management - Allasan Cobblah, MS, Cost Control for the Mineral Industries. Mineral Processing - Hun-Saeng Chung, MS, The Use of Sedimentation Methods for Particle Size Analysis in the Sub-Micron Range; Romel J. Mirville, MS, The Interaction of Blackwater Constit-
JOURNAL OF METALS • July, 1979
uents with Polymeric Flocculants; Keith Dale Mondale, MS, The Characterization, Beneficiation, and Ion Exchange Properties of Natural Sedimentary Zeolites; Kevin Charles Thompson, MS, The Influence of Point Defects on the Flotation of Lead Sulfide.
Amax Supports Mineral Processing Scholarship Program at Penn State The Mineral Processing Section of the Department of Mineral Engineering at Penn State University received a grant of $1,000 from AMAX Extractive Research and Development, Inc., Golden, Colo., for support of undergraduate scholarships in mineral processing. 39
