选区激光熔化高强韧铝合金的异质结构调控及力学性能

Heterogeneous Structure and Mechanical Properties of Strong and Tough Al Alloys Prepared by Selective Laser Melting

同时采用共晶成分设计和晶粒细化的策略,通过异质结构调控提升SLM成形的Al-Fe系列合金的强韧性。结果表明,SLM成形AlFe_(5)合金呈现柱状粗晶和等轴细晶并存的组织结构,其中细晶的体积分数较低,整体显微结构未表现出明显的非均匀性;随着Zr元素的添加,SLM成形AlFe_(5)Zr_(1)合金中细晶体积分数增加,呈现粗、细晶交替分布的非均匀异质结构。同时,SLM成形AlFe_(5)和AlFe_(5)Zr_(1)合金在纳米尺度均呈现胞状结构特征。这种纳米级胞状结构、过饱和Fe元素及高位错密度主导的强化机制使得SLM成形Al-Fe-Zr系列合金的屈服强度达400 MPa,且异质结构可进一步提升AlFe_(5)Zr_(1)合金的应变强化能力,使其抗拉强度达450 MPa。原位断裂韧性测试结果表明,异质结构可促使裂纹在扩展过程中发生偏折和尖端钝化,从而增加裂纹扩展阻力,使AlFe_(5)Zr_(1)合金具有优异的断裂韧性。

Aluminum alloys have been widely used in fields such as automotive and aerospace industries,owing to their excellent mechanical properties,lightweight,and low recycling costs.However,aluminum alloys processed by selective laser melting(SLM)typically suffer from insufficient strength and fracture toughness.To tackle this issue,a new strategy that integrates eutectic composition design and grain refinement has been adopted to create a heterogeneous structure that can improve strength and toughness of SLMed Al-Fe_(5)-Zr alloys.The SLMed AlFe_(5)5 alloy consists of high-volume-fraction of coarse and columnar grains and low-volume-fraction of fine grains,and no obvious heterogeneity is visible across the microstructure length scale.With the addition of Zr,the volume fraction of fine grains significantly increases,leading to the heterogeneous distribution of coarse and fine grains in the SLMed AlFe_(5)5Zr_(1) alloy.Meanwhile,both AlFe_(5)5 and AlFe_(5)5Zr_(1) alloys show a nanoscale cellular structure.This type of a nanosized cellular structure,together with supersaturated Fe_(5) and high-density dislocations,contributes to a high yield strength of 400 MPa for the SLMed AlFe_(5)Zr alloys.The heterogeneous structure can further improve the strain strengthening capability,enabling a tensile strength as high as 450 MPa for the AlFe_(5)5Zr_(1) alloy.Furthermore,the heterogeneous structure promotes crack deflection and crack tip blunting,which can effectively increase crack growth resistance and impart superior fracture toughness to the AlFe_(5)5Zr_(1) alloy.