The improvement of microstructure and mechanical properties of Ti alloys is of great significance for their industrial application. In this study, a developed multi-step hot deformation process was employed to regulate the grain boundaries (GBs), hetero-phase boundaries (PBs) and dislocation structure for dual-phase titanium alloy. The effects of accumulative thermal deformation ratios from 33% to 75% (2–8 cycles) on the microstructure and mechanical properties have been investigated. It is found that the sintered sample shows a typical Widmanstätten structure without obvious pores and micro-cracks. However, with the increase of the deformation ratio, for the hexagonal close packed (HCP) Ti, the crystal orientations of {} and {} were gradually transformed into {0001}, with the change of high-angle grain boundaries (HAGBs) to low-angle grain boundaries (LAGBs). The density of stored geometrically necessary dislocations (GNDs) density raised dramatically from 1.95×10 m to 6.5×10 m, and various types of dislocations have been characterized. For the β phase, in the thermal deformation process, high density α´-precipitates with an average thickness below 20 nm had formed with Burgers relationship of {110}//{0001} and < >//< >. Finally, the yield strength of the dual-phase titanium alloy increased dramatically from 881 MPa to 1178 MPa, and the ductility can still maintain at above 8.5%. The enhanced strength was mainly contributed by the increase of geometrically necessary boundaries (GNBs) and nano-lamellae boundaries (NLBs). Therefore, this strategy of combining hetero-phase boundaries (PBs) and dislocation engineering could open up new avenues to designing strong and ductile titanium matrix materials.

中文翻译：

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累积热轧对SPS烧结固结双相钛合金显微组织和力学性能的影响

钛合金显微组织和力学性能的改善对其工业应用具有重要意义。在这项研究中，采用了一种开发的多步热变形工艺来调节双相钛合金的晶界（GB）、异相边界（PB）和位错结构。研究了 33% 至 75%（2-8 个循环）的累积热变形率对显微组织和机械性能的影响。结果发现，烧结样品呈现典型的魏德曼组织结构，没有明显的气孔和微裂纹。然而，随着变形率的增加，对于六方密堆积（HCP）Ti，{}和{}的晶体取向逐渐转变为{0001}，高角度晶界（HAGB）转变为{0001}。小角度晶界（LAGB）。存储的几何必要位错（GND）密度从1.95×10 m显着提高到6.5×10 m，并且已经表征了各种类型的位错。对于β相，在热变形过程中，形成了平均厚度低于20 nm的高密度α´-析出物，其Burgers关系为{110}//{0001}和< >//< >。最终，双相钛合金的屈服强度从881 MPa大幅提高到1178 MPa，而塑性仍能保持在8.5%以上。强度的增强主要是由于几何必要边界（GNB）和纳米片晶边界（NLB）的增加。因此，这种将异相边界（PB）和位错工程相结合的策略可以为设计坚固且延展的钛基材料开辟新途径。