The interrelationship of fracture toughness and microstructure in a Ti-5.25Al-5.5V-0.9Fe-0.5Cu alloy
- PDF / 2,280,623 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 2 Downloads / 208 Views
[1]
= the f r a c t u r e s t r e s s of an equiaxed ~ aged/3 s p e c i m e n c o r r e c t e d for n e c k ing to obtain the a x i a l f r a c t u r e s t r e n g t h
d
= the equiaxed ~ t r a v e r s e p a r t i c l e diameter
~,
= m e a n f r e e path b e t w e e n a p a r t i c l e s
D
= $ matrix grain diameter
go, Kd, K D , KA. a r e c o n s t a n t s . Experimentally determined fracture strengths were found to fall within 10 pct of those p r e d i c t e d by Eq. [1], and f r a c t u r e s t r e n g t h was found to be l i m i t e d by void f o r m a t i o n . D u c t i l i t y , in the f o r m of r e d u c t i o n of a r e a was d e t e r m i n e d by the s p r e a d between the yield s t r e n g t h and f r a c t u r e s t r e n g t h . R e s u l t s of void f o r m a M. A. GREENFIELD and H. MARGOLIN are Graduate Student and Professor of MetallurgicalEn~neering, respectively, Department of Metallurgy and Materials Sciences, School of Engineering and Science, New York University, New York, N.Y. This paper is based on a thesis to be submitted by M. A. GREENFIELD in partial fulfillment of the requirements for the Ph.D. degree in metallurgy at New York University. Manuscript submitted June 15, 1970. METALLURGICALTRANSACTIONS
tion and growth s t u d i e s will be published in a s e p a r a t e paper.2 As p a r t of this c o n t i n u i n g study, the role of m i c r o s t r u c t u r e in d e t e r m i n i n g f r a c t u r e t o u g h n e s s was i n v e s t i g a t e d . C r o a n and R i z z i t a n o s had shown that f o r g ing in the /3 field and q u e n c h i n g to produce a t r a n s f o r m a t i o n s t r u c t u r e , s i g n i f i c a n t l y i m p r o v e d C h a r p y vnotch e n e r g y v a l u e s . A l s o , G e r b e r i c h 4 m o r e r e c e n t l y showed that the f r a c t u r e t o u g h n e s s was e n h a n c e d by an a c i c u l a r s t r u c t u r e and p r o p o s e d a f r a c t u r e m e c h a n i s m b a s e d on c r a c k tip d i s p l a c e m e n t s . The t e n d e n c y for c r a c k s in T i - 6 A1-4 V s p e c i m e n s to follow a - ~ i n t e r f a c e s was noted by G e r b e r i c h and is to be d i s c u s s e d m o r e fully in the following. EXPERIMENTAL
PROCEDURE
12 Ib, 3~ in. diam Ti-5.25 AI-5.5 V-0.9 Fe-0.5 Cu ingots were arc melted from 86 Bhn sponge, 99.9 pct Fe, Cu, and A1 and Union Carbide master alloy VQ, nominally 85 pct V-15 pet AI. Impurities from the master alloy amounted to 0.1 pct. The ingots were initially extruded in the ~ field at reductions of 15:1 and 11.7:1 from an initial diameter of 2.95 in. The ~ transus was 1700~ Final working consisted of swaging from the extruded diameter to 0.77 in. at 1400~ Standard 0.250 in. diam tensile specimens and standard Charpy v-notch blanks were prepared after heat treatments consisting of a final solution treatment at 1625~ in v a c u o plus water quench, followed by aging for 1 hr at 1150~ and air cooling. T i m e s at 1625~ were varied from 3 to 48 hr in order to obtain desired microstructures. Fracture to
Data Loading...
