Grain Boundary α and β Grain Boundary Orientation in Titanium Alloys

Abstract

The formation of grain boundary in titanium alloys has been extensively investigated in the past since its morphology, crystallography and distribution affect the mechanical behavior of titanium alloys. It is known that grain boundary forms with the Burgers orientation relationship to one the grains on either side of the grain boundary and therefore can form with 24 possible variants arising from this orientation relationship. The criteria for variant selection have been explored but lack of knowledge on the grain boundary plane in prior investigations has inhibited a complete understanding of the variant selection process. In this study we have developed a technique using EBSD and stereo pair imaging to relate crystallography to the prior grain boundary plane and reexamine the criteria for variant selection.

Hierarchical criteria to promote fast and selective αGB precipitation at β grain boundaries in β-metastable Ti-alloys

“…The corresponding {334} HPs are listed in the right column. The HP has also been proposed to play a role in the selection of the a layer forming at a b GB: the a GB is considered to preferentially form if its HP is close to the prior b GBP [10].…”

“…Recently, the HP VS criterion was analyzed by 3D analysis at one GB of a triple junction for a water quenched Ti-64 [10]. The HP was assumed to be of {556} b type (it was defined by the plane containing the lattice invariant direction <335> b and the One could thus question about the fraction of GBs able to potentially respect this HP condition.…”

“…Also, VS analysis requires statistics. Especially, results on the role of the 3D GB character are often limited to few GB configurations as they require time-consuming 3D imaging analysis [10,11]. Moreover, the transformation kinetics is rarely taken into account.…”