Fundamental and Application‐Oriented Research on Gamma Alloys

Abstract

Recent activities of 7 -T i A l related research at I M R is reviewed in this p a p e r . O n t h e f u n d a m e n t a l side, first principles computations were performed t o relate site occupancies and atomic interactions t o t h e mechanisms of s t r e n g t h e n i n g and phase t r a n s f o r m a t i o n , and to u n d e r s t a n d surface adsorption of oxygen a n d oxidation. D e f o r m a t i o n f u n d a m e n t a l s such as nucleation of superdislocations in t h e 7 phase were studied t h r o u g h molecular d y n a m i c s modeling. O u r application-oriented work covers extrusion a n d n e t -s h a p e forming t h a t includes b o t h precision casting a n d powder metallurgy. T h e evolution of textures d u r i n g t h e coupled process of deformation, phase transformation, recrystallization a n d grain g r o w t h during extrusion and subsequent heat t r e a t m e n t was characterized a n d related to mechanical properties. Centrifugal casting was employed to obtain quality p a r t s having thin sections b u t large size in 1-or 2-dimensions, a n d t h e problems such as misrun, cavities, surface porosity a n d inclusion as well as dimension distortion were tackled. Powder metallurgy was studied essentially as a technology u p g r a d e of precision casting, forming c o m p o n e n t s of complex s h a p e .