BRIEF
COMMUNICATIONS
EFFECT
OF
CERTAIN
TEMPEBATURE I. F .
MEDIA
PLASTICITY
Divisenko
and
ON T H E
HIGH-
OF TITANIUM
Yu.
UDC 669.295:620.171+532:6;539.375
M. K o r e n y u k
C o m m e r c i a l g r a d e VT1-O t i t a n i u m was subjected to tensile t e s t s in the 700-1000~ t e m p e r a t u r e i n t e r val An a i r , i n v a c u u m , a n d i n m e l t s of aluminum and an aluminum alloy containing 6% of magnesium by weighL Specimens with an effective section 6 m m in d i a m e t e r were used in quintuplicate f o r this purpose. They were deformed in a i r and in molten media on an R-5 t e n s i l e - t e s t i n g machine. F o r testing in the aluminum m e l t s and m e l t s of the a l u m i n u m - m a g n e s i u m alloy, we used special ampuls filled with the r e s p e c t i v e melt. V a c uum testing was accomplished in a PRV-302 apparatus with the c h a m b e r evacuated to 1 ~10 -s m m Hg. The specimens were deformed at an elongation rate of 4%/rain. The relative elongation of the m a t e r i a l was d e t e r m i n e d f r o m the r e s u l t s of t e s t s of 3-5 specimens in alternate r e g i m e s (see Table 1). Tensioned in air, c o m m e r c i a l titanium displays i n c r e a s e d plasticity in the 900*C t e m p e r a t u r e region, where the m a t e r i a l undergoes a polymorphic t r a n s f o r m a t i o n . On deforming the titanium in the a l u m i n u m m e l t , the interval of i n c r e a s e d plasticity shifts in the direction of lower t e m p e r a t u r e s . A s i m i l a r shift effect of the interval of i n c r e a s e d plasticity of the m a t e r i a l at t e m p e r a t u r e s below the p o l y m o r p h i c - t r a n s f o r m a t i o n t e m p e r a t u r e is noted f o r pure titanium [1]. In our c a s e , the aluminum is a reducing agent with r e s p e c t to the titanium. The heating and deforming of the titanium in the molten aluminum is t h e r e f o r e accompanied by both a reduction in its oxygen content and the p r o t e c t i o n of the surface from oxygen; this m a y apparently explain the observed shift effect. When the titanium is tensioned in the a l u m i n u m - m a g n e s i u m melt, the t e m p e r a t u r e interval of increased m a t e r i a l plasticity broadens c o n s i d e r a b l y as compared with the interval obtained when testing in air; in this c a s e , the resultant c h a r a c t e r i s t i c s of the plastic p r o p e r t i e s approach the s i m i l a r c h a r a c t e r i s t i c s of the t i tanium in a vacuum. The expansion of the t e m p e r a t u r e interval of i n c r e a s e d plasticity in the direction of lowe r t e m p e r a t u r e s may o c c u r as a r e s u l t of the p r o c e s s e s that we will examine here. The simultaneously high p l a s t i c i t y of the m a t e r i a l at the point of polymorphic t r a n s f o r m a t i o n s during t e s t s in air, in vacuum, and inthe a l u m i n u m - m a g n e s i u m melt may be hypothetically governed by the effect of hydrogen. These media tend to purify titanium of hydrogen, while molten aluminum, c o n v e r s e l y , contributes to its saturation. TABLE 1 Relative elongation (%) at temperatare (~
Test medium
700
900
IO00
44___~56 68~076 88--108 1100 60--76 70
Air Molten A1
800
g8-,08,04-,07
~
--105
"
Melt of A1 ~11 . . . . . . containt~{.-109--112 110--125 86-10995 657:8 allo~ lrg ~ wt. % 110 115 rag 1-10 -smm 120--130 145--165 100-152 43--110 Hg vacuum ~ ~ ~ Note. Minimum and m a x i m u m values a r e given in the n u m e r a t o r and a v e r a g e values of 3-4 m e a s u r e m e n t s , in the denominator. T r a n s l a t e d f r o m Ftziko-Khimicheskaya Mekhanika Materialov, Vol. 13, No. 1, pp. 114-115, J a n u a r y F e b r u a r y , 1977. Original article submitted May 15, 1975. This material is protected by copyright registered in the name o f Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $ 7.50.
i01
Fig. 1. Structure of contact boundary between molten aluminum and solid titanium
(x6OO). A metallographic study of titanium that had been subjected to the action of the molten aluminum and aluminum--magnesium alloy was conducted on microsections cut from the effective section of specimens p e r pendicular to the longitudinal axis. After holding the titanium in these melts both with and without a load, a new structural component was observed on the contact boundary between the solid and molten metals (see Fig. 1). It was established by methods of x - r a y structural and x - r a y m i c r o s p e c t r a l analyses and by m e a suring the microhardness that this structural component is the intermetallide compound TiA89 Having m a t e rialized, this compound breaks down immediately, forming fragments 5 - 2 5 # in size. At 800~ and in the absence of a load for 6 h, the thickness of the intermetallide compound reaches 1 nun. Breakdown of the intermetallide i n t e r l a y e r occurs most likely as a result of vigorous penetration of the melt along the crystallite boundaries, as in the case of the action of molten copper on solid iron [2]. It should be noted that on heating a bimetallic titanium-aluminum compound in the solid phase, a r a t h e r homogeneous interlayer of the i n t e r metallide compound TiA89 whose thickness is determined by the heating temperature and holding time, forms on t h e b o u n d a r i e s of these compounds. Thus, these studies demonstrated that the plasticizing effect of molten aluminum and its alloy containing 6% of magnesium by weight appears in the temperature region up to 900~ With a further increase in test temperature, the plasticity of the titanium in contact with the molten metal diminishes, being virtually the same as the plasticity of the titanium in air. LITERATURE 1. 2.
102
CITED
A . A . Presnyakov, Superplasticity of Metals and Alloys [in Russian], Nauka, Alma-Ata (1969). V . L . Kolmogorov, V. A. Chichigin, V. G. Burdukovskii, and B. M. Antoshechkin, Metal Series [in Russian], No. 1, Izv. Akad. Nauk SSSR (1976), pp. 70-74.