β型Ti-15Mo合金中α相变体选择

Variant selection ofαphase in β-type Ti-15Mo alloy

利用SEM、EBSD等方法研究了固溶时效后Ti-15Mo合金中β基体和晶界处析出α相的变体选择行为。结果表明,固溶态试样由无择优取向的单一β晶粒构成。固溶时效态试样中晶内α相不发生变体选择,但晶内α相变体之间存在自协调现象,并导致各α相变体呈现60°交叉状分布。膜状晶界α相的变体选择受到相邻β晶粒间取向差的影响,取向差较小时会与两侧的β晶粒均保持Burgers取向关系,而取向差较大时会受到界面取向的影响。晶界魏氏组织的变体选择取决于形核位置,形核于膜状晶界α相的魏氏组织选择与晶界α相相同的变体,形核于膜状晶界α相与β基体界面处的魏氏组织同时受到两者的共同影响。

SEM and EBSD were used to investigate the variant selection behaviour of theαphase in theβmatrix and at theβgrain boundaries in the Ti-15Mo alloy after solution treatment and aging.The results show that the solution treated specimen consists of singleβgrains without any preferred orientation.In the solution treated and aged specimen,the intragranularαphase does not undergo variant selection,instead,self-accommodation occurs amongαvariants,leading to a cross distribution ofαphase variants at 60°.The variant selection of the film-like grain boundaryαphase is influenced by the misorientation of adjacentβgrains.A minor misorientation causesαphase to retain a Burgers orientation relationship withβgrains on either side,whereas a major misorientation affects the precipitation of theαphase due to the interface orientation.The variant selection of the grain boundary Widmanstatten microstructure relies on the nucleation site.When the nucleation takes place at the film-like grain boundaryαphase,it selects the same variants as the film-like grain boundaryαphase.Nonetheless,when the nucleation occurs at the interface between the film-like grain boundaryαphase and theβmatrix,it is influenced by both.