Unusual precipitation induced by solute segregation in coherent twin boundary in titanium alloys
Unusual precipitation induced by solute segregation in coherent twin boundary in titanium alloys
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DOI：
10.1016/j.actamat.2022.118466
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发表时间：
2022-10
期刊：
影响因子：
9.4
通讯作者：
Chaoqiang Liu;Xingye Hu;Lin Qi;Houwen Chen;Zhiqiao Li;Xiaoyong Zhang;Hongge Yan;Kechao Zhou;M. Song;Yunzhi Wang;J. Nie
中科院分区：
文献类型：
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作者：
Chaoqiang Liu;Xingye Hu;Lin Qi;Houwen Chen;Zhiqiao Li;Xiaoyong Zhang;Hongge Yan;Kechao Zhou;M. Song;Yunzhi Wang;J. Nie
α+ β钛合金中α相和β相的不均匀析出及其分布对合金的力学性能有很大影响。通常观察到β相在α′马氏体板和马氏体内部位错之间的边界处不均匀地沉淀，特别是在增材制造的α+ β钛合金中，与周围的基体相具有Burgers取向关系。本文报道了Ti-4wt%Mo合金中一个有趣的现象，即β相在α′马氏体中Mo偏聚的{10 1 <$1}全共格孪晶界（CTB）上不均匀析出，并与α′具有不寻常的Potter取向关系。发现CTB具有类似β相的结构，Mo在CTB中的偏聚导致偏聚的原子柱发生异常的面外位移，使局部结构与β结构几乎相同，从而作为β沉淀的模板，具有独特的取向关系。我们的研究结果揭示了一种新的机制，通过该机制可以有效地控制β析出物的分布以获得更好的机械性能，并且可以扩展到一组钛合金，包括当前的主力合金Ti-6Al-4V，以及更广泛地扩展到其他工程合金。
Heterogeneous precipitation and hence the distribution of α and β phase in α+ β titanium alloys can impact strongly on alloy mechanical properties. The β phase is commonly observed to precipitate heterogeneously at boundaries between α′ martensite plates and dislocations inside the martensite, especially in the additively manufactured α+ β titanium alloys, with a Burgers orientation relationship with the surrounding matrix phase. Here, we report an interesting phenomenon in a Ti-4wt% Mo alloy where the β phase precipitates heterogeneously on Mo-segregated {10 1¯ 1} fully coherent twin boundaries (CTBs) within α′ martensite, with an unusual Potter orientation relationship with α′. We find that the CTB has a structure resembling that of the β phase and that Mo segregation in the CTB leads to an unusual out-of-plane shift of the segregated atomic columns that makes the local structure almost identical to the β structure, hence serving as a template for β precipitation with the unique orientation relationship. Our findings reveal a novel mechanism via which the distribution of β precipitates can be manipulated effectively for better mechanical properties and could be extended to a group of Ti alloys including the current workhorse alloy Ti-6Al-4V and more broadly to other engineering alloys.