The strain rate dependence of mechanical property in a selective laser melted (SLM) 17–4 precipitation hardening (PH) stainless steel with different states was investigated systematically by microstructure characterization, texture measurement and tensile test in the present study. The results reveal that as-built and annealed specimens have different initial microstructure and show the strain rate dependence of mechanical property, and their microstructure and texture have great changes during tensile deformation. Before tensile deformation, both as-built and annealed specimens are comprised of mixed grain structure, texture along building direction and dual austenite and martensite phases, however, the latter contains a larger amount of martensite phase. No matter as-built specimen or annealed specimen, the yield strength, ultimate tensile strength and elongation increase with the increase of strain rate. In contrast to the as-built specimen, the annealed specimen exhibits the higher ultimate tensile strength, but lower elongation at the corresponding strain rate, and the higher strain rate sensitivity. After the tensile deformation, the completely different microstructure and texture were developed including finer grain structure, more high angle grain boundaries (HAGBs), new texture along tensile direction and more martensite phase. There is a significant austenite-to-martensite phase transformation during tensile deformation. No matter as-built specimen or annealed specimen subjected to tensile deformation, the grain size, HAGBs and texture almost have no change with the increase of strain rate, but the phase transformation degree changes a lot.

通过微观结构表征，织构测量和拉伸试验，系统地研究了不同状态的选择性激光熔融（SLM）17-4沉淀硬化（PH）不锈钢的力学性能对应变率的依赖性。结果表明，建成后和退火后的试样具有不同的初始微观结构，并显示出应变率对机械性能的依赖性，并且它们的微观结构和织构在拉伸变形过程中有很大的变化。在拉伸变形之前，建成和退火的试样均由混合晶粒结构，沿构造方向的织构以及双奥氏体和马氏体相组成，但是后者包含大量的马氏体相。无论是试件还是退火试件，屈服强度，极限抗拉强度和伸长率随着应变率的增加而增加。与制成的试样相反，退火试样表现出较高的极限抗拉强度，但在相应的应变速率下伸长率较低，并且应变速率灵敏度较高。拉伸变形后，形成了完全不同的微观结构和织构，包括更细的晶粒结构，更大的高角度晶界（HAGB），沿拉伸方向的新织构和更多的马氏体相。在拉伸变形过程中，奥氏体向马氏体有明显的相变。无论是试件还是退火试样，均会发生拉伸变形，其晶粒尺寸，HAGBs和织构几乎都不会随应变速率的增加而变化，但相变程度却发生了很大的变化。