The unique thermal history of different metal additive manufacturing processes would have profound impacts on the resulting microstructure and material properties. However, few have conducted benchmark research on the impacts. This work provides a comprehensive benchmark comparison on microstructure, mechanical properties, and their underlying mechanisms in selective laser melting (SLM), electron beam melting (EBM), and mill-annealing of Ti–6Al–4V alloys. The results have shown that the SLMed and EBMed samples possess very fine acicular α′ martensite while the conventional mill-annealed ones have granular α phase. The SLMed samples exhibit the highest tensile and yield strength resulted from the combined effects of refined α’ martensite and high microscale residual stress. The lowest tensile and yield strength and intermediate elongation of the EBMed samples are attributed to the relatively high number of type-II pores and in-situ annealing for residual stress relief during the printing process. The mill-annealed samples have the highest elongation due to the fully dense structure, the negligible microscale residual stress, and favorable grain orientation. It is expected to improve the ductility of SLMed samples via appropriate post-annealing and enhance the strength of EBMed samples by reducing the number of type-II pores through process optimization. The fundamental differences in microstructure and properties are attributed to the unique thermal histories of the concerned processes.

不同金属增材制造工艺的独特热历史将对所得的微观结构和材料性能产生深远的影响。但是，很少有关于影响的基准研究。这项工作对Ti-6Al-4V合金的选择性激光熔化（SLM），电子束熔化（EBM）和轧制退火中的微观结构，力学性能及其潜在机理进行了全面的基准比较。结果表明，SLMed和EBMed样品具有非常细的针状α'马氏体，而常规的退火退火样品则具有颗粒状α相。SLMed样品表现出最高的拉伸强度和屈服强度，这是由于精制的α'马氏体和高微观残余应力共同作用的结果。EBMed样品的最低拉伸强度，屈服强度和中间伸长率归因于相对大量的II型孔和原位退火，以减轻印刷过程中的残余应力。由于完全致密的结构，可忽略的微观残余应力和良好的晶粒取向，经过铣削退火的样品具有最高的伸长率。期望通过适当的后退火处理来提高SLMed样品的延展性，并通过工艺优化减少II型孔的数量，从而提高EBMed样品的强度。微观结构和性能的根本差异归因于有关工艺的独特热历史。