激光选区熔化成形Al-Mg-Sc-Zr合金孔隙缺陷对拉伸性能的影响研究

Effect of Pore Defects on Tensile Properties of Al-Mg-Sc-Zr Alloy Formed by Selective Laser Melting

激光增材制造合金内部存在的孔隙缺陷会对合金的力学性能产生不利影响。为研究激光选区熔化(SLM)成形Al-Mg-Sc-Zr合金中孔隙缺陷对其拉伸性能的影响,通过SLM成形技术制备了Al-Mg-Sc-Zr合金试样,利用X射线计算机断层扫描技术表征了合金内部孔隙缺陷的三维特征,并通过室温拉伸试验获得了合金的拉伸性能。基于SLM成形Al-Mg-Sc-Zr合金的孔隙数据及室温拉伸试验结果,建立能够反映材料本构以及孔隙特征的代表体积单元(RVE)模型,在SLM成形Al-Mg-Sc-Zr合金基体保持不变的情况下,通过改变RVE模型中的孔隙率和孔隙尺寸研究孔隙对SLM成形Al-Mg-Sc-Zr合金拉伸性能的影响。计算结果表明:当孔隙率增加时,合金的抗拉强度和弹性模量明显降低;当孔隙尺寸增大时,合金的抗拉强度明显降低,但弹性模量没有明显变化;当孔隙尺寸增大到一定程度(大于100μm)时,孔隙周围会出现明显的应力集中。

Pore defects adversely affect the mechanical properties of laser-additive manufacturing alloys.To elucidate the effect of pore defects on the tensile properties of Al-Mg-Sc-Zr alloy formed by selective laser melting(SLM),this study characterizes the internal pore defects of the alloy in three dimensions using X-ray computed tomography and obtains the tensile properties of the alloy through room-temperature tensile tests.Based on the pore data and tensile-test results of the Al-Mg-Sc-Zr alloy,a representative volume element(RVE)model that reflects the constitutive and pore characteristics of the material is established.Assuming an unchanging matrix of the Al-Mg-Sc-Zr alloy formed by SLM,the tensile properties of the alloy are evaluated for different porosities and pore sizes in the RVE model.The calculations show that the tensile strength and elastic modulus of the alloy decrease obviously when the porosity increases.And,when the pore size increases,the tensile strength of the alloy decreases significantly,but the elastic modulus does not change significantly.When the pore size exceeds 100μm,obvious stress concentration appears around the pores.