Lawrence Livermore National Laboratory, Livermore, California, 94550, USA.
Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts, 01003, USA.
Nat Commun. 2019 Sep 25;10(1):4338. doi: 10.1038/s41467-019-12265-8.
Additively manufactured (AM) metallic materials commonly possess substantial microscale internal stresses that manifest as intergranular and intragranular residual stresses. However, the impact of these residual stresses on the mechanical behaviour of AM materials remains unexplored. Here we combine in situ synchrotron X-ray diffraction experiments and computational modelling to quantify the lattice strains in different families of grains with specific orientations and associated intergranular residual stresses in an AM 316L stainless steel under uniaxial tension. We measure pronounced tension-compression asymmetries in yield strength and work hardening for as-printed stainless steel, and show they are associated with back stresses originating from heterogeneous dislocation distributions and resultant intragranular residual stresses. We further report that heat treatment relieves microscale residual stresses, thereby reducing the tension-compression asymmetries and altering work-hardening behaviour. This work establishes the mechanistic connections between the microscale residual stresses and mechanical behaviour of AM stainless steel.
增材制造（AM）的金属材料通常具有显著的微尺度内应力，表现为晶间和晶内残余应力。然而，这些残余应力对 AM 材料的机械性能的影响仍未得到探索。在这里，我们结合同步辐射 X 射线衍射实验和计算建模，在单轴拉伸下定量测量 AM 316L 不锈钢中具有特定取向的不同晶粒族的晶格应变和相关的晶间残余应力。我们测量了打印不锈钢屈服强度和加工硬化的明显拉压不对称性，并表明它们与源自不均匀位错分布和由此产生的晶内残余应力的背应力有关。我们进一步报告说，热处理可以消除微尺度残余应力，从而降低拉压不对称性并改变加工硬化行为。这项工作建立了 AM 不锈钢的微观残余应力和机械性能之间的机械联系。
