Ali Haider, Ghadbeigi Hassan, Mumtaz Kamran
Department of Mechanical Engineering, University of Sheffield, Sheffield, UK.
J Mater Eng Perform. 2018;27(8):4059-4068. doi: 10.1007/s11665-018-3477-5. Epub 2018 Jul 17.
Selective laser melting (SLM) process is characterized by large temperature gradients resulting in high levels of residual stress within the additively manufactured metallic structure. SLM-processed Ti6Al4V yields a martensitic microstructure due to the rapid solidification and results in a ductility generally lower than a hot working equivalent. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. Residual stress buildup and the mechanical properties of SLM parts can be controlled by varying the SLM process parameters. This investigation studies the effect of layer thickness on residual stress and mechanical properties of SLM Ti6Al4V parts. This is the first-of-its kind study on the effect of varying power and exposure in conjunction with keeping the energy density constant on residual stress and mechanical properties of SLM Ti6Al4V components. It was found that decreasing power and increasing exposure for the same energy density lowered the residual stress and improved the % elongation of SLM Ti6Al4V parts. Increasing layer thickness resulted in lowering the residual stress at the detriment of mechanical properties. The study is based on detailed experimental analysis along with finite element simulation of the process using ABAQUS to understand the underlying physics of the process.
选择性激光熔化（SLM）工艺的特点是温度梯度大，这会在增材制造的金属结构中产生高水平的残余应力。由于快速凝固，经SLM工艺处理的Ti6Al4V会产生马氏体微观结构，其延展性通常低于热加工等效物。可以对SLM部件进行后处理热处理，以消除内置的残余应力并提高延展性。通过改变SLM工艺参数，可以控制SLM零件的残余应力积累和机械性能。本研究探讨了层厚对SLM Ti6Al4V零件残余应力和机械性能的影响。这是同类研究中首次探讨在保持能量密度恒定的情况下，改变功率和曝光量对SLM Ti6Al4V部件残余应力和机械性能的影响。研究发现，对于相同的能量密度，降低功率并增加曝光量可以降低残余应力，并提高SLM Ti6Al4V零件的伸长率。增加层厚会导致残余应力降低，但会损害机械性能。该研究基于详细的实验分析以及使用ABAQUS对该过程进行的有限元模拟，以了解该过程的基本物理原理。
