马氏体是选区激光熔化TC4的常见物相， 其分解过程调控对优化成形件性能尤为重要。 采用激光扫描 SLM-TC4 全 α′ 马氏体试样，对沉积态试样施加不同热循环，结合数值模拟分析不同热循环条件下的α′马氏体相变序 列，明确了α′→β高温 →(α+β)与 α′→(α+β)两种转变路径及其组织特征，前者的α相不再具有α′的层级结构，而表现为 魏氏集束与网篮组织的混合形态，后者的α相继承了马氏体的晶体取向和层级结构。在第二种转变路径条件下，当热循 环温度逼近β转变温度且峰谷温差值较大时，α′马氏体可以在较短时间内依赖孪晶界完成分解，进而形成细小的球化 α 相，有助于选区激光熔化TC4合金的性能提升。

 α′ martensite is the major phase in selective laser melted TC4 alloy, and the controlling of its decomposition is very important for the optimization of the formed components. Laser scanning was applied to the SLM-TC4 samples with full α′ martensite microstructure, the thermal history curves at different locations of the samples were derived with the aid of numerical simulations, and the phase transformation sequence of α′ martensite under thermal cycling conditions was analysed. Two transformation pathways are identified: α′→β→(α+β) and α′→(α+β), with different thermal histories. In the former pathway, the α phase no longer maintains the hierarchical structure of α′, which typically exhibits a mixed morphology of Widmanstätten colonies and basketweave structures. In the latter pathway, the α phase retains the crystallographic orientation and hierarchical structure of the martensite. It has also been shown that in the second transformation pathway, when the temperature of thermal cycling approaches βtr and the temperature difference between the peak and valley is significant, the decomposition of α′ martensite and the globalization of the α phase are accelerated, with β precipitating at the twin boundaries, which can further contribute to the enhancement of the properties of the SLM TC4 components.