Concurrent design for NiAl-based (β/γ′) two-phase alloys by controlling microstructure and texture

Toshiya Sakata, Hiroyuki Yasuda, Yukichi Umakoshi
2002 Science and Technology of Advanced Materials  
Control of the crystallography of Ni 3 Al(g 0 ) precipitates along grain boundaries of NiAl(b) was systematically studied using b bicrystals with controlled orientations. g 0 phase preferentially precipitated along b grain boundaries showing a ®lm-like shape. The variants of g 0 precipitates were uniquely selected, which satis®es the Kurdjumov±Sachs (K±S) relation with a neighboring b grain and deviates from the relation with another adjacent b grain. In the course of tensile deformation,
more » ... deformation, fracture occurred preferentially at the (b/g 0 -®lm) interface deviating from the K±S relation and the fracture stress decreased with increasing deviation angle from the K±S relation. For improvement of the coherency at the irrational (b/g 0 -®lm) boundaries, the control of microstructure and crystal orientation distribution in (b/g 0 ) two-phase polycrystals was next attempted by thermomechanical processing. After hot-compression in b phase region and subsequently annealing in (b/g 0 ) two-phase region, g 0 phase transformed from b phase with k111l b ®ber texture satisfying the K±S relation, resulting in the formation of k110l g 0 ®ber texture. In particular, a large number of (b/g 0 -®lm) boundaries became partially coherent. This thermomechanical processing was effective in controlling the crystallography of g 0 -®lm along b grain boundaries and leads to the harmonic design of strength and ductility for (b/g 0 ) two-phase alloys. q
doi:10.1016/s1468-6996(02)00006-2 fatcat:pcsn5fikx5gqlipgqw2gymteji