激光选区熔化AlSi7Mg合金高周疲劳性能研究

Research on High Cycle Fatigue Performance of AlSi7Mg Alloy Fabricated by Selective Laser Melting

为研究激光选区熔化(SLM)成形AlSi7Mg合金的高周疲劳性能,对合金沉积态试样进行静态拉伸试验和不同应力载荷的疲劳试验,通过金相显微镜和电子显微镜观察试样微观组织和疲劳断口形貌,并探究疲劳失效机理。结果表明,SLM AlSi7Mg试样的拉伸性能明显高于铸造AlSi7Mg,且抗拉强度和屈服强度均小于SLM AlSi10Mg,但二者疲劳极限相当。与传统制备方法相比,试样微观组织分为三个区域:细晶区、粗晶区和热影响区,Si相呈网状结构均匀嵌入α-Al基体中。通过断口分析,发现SLM成形AlSi7Mg试样的疲劳裂纹在气孔和夹杂物等缺陷处萌生,呈半圆形向四周放射状扩展,在剩余截面无法承受疲劳载荷时试样瞬间断裂,瞬断区具有解理面和韧窝的形貌特征。将SLM AlSi7Mg沉积态与SLM AlSi10Mg沉积态进行对比发现,二者拉伸性能和疲劳性能目前在宏观上差异较小,SLM成形试样的微观组织相似且均含大量分散的缺陷。

In order to study the high-cycle fatigue properties of AlSi7Mg alloy fabricated by selective laser melting(SLM),the static tensile test and fatigue test under different stress loadings were performed on the as-built specimens.The microstructure and fatigue fracture morphology of the as-built specimens were observed by metallographic microscope and electron microscope,and the fatigue failure mechanisms were investigated.The results show that the tensile properties of SLM AlSi7Mg specimens are significantly higher than those of cast AlSi7Mg,and the tensile strength and yield strength are lower than those of SLM AlSi10Mg,but their fatigue limits are similar.Compared with traditional manufacturing method,the microstructure of the specimens is divided into three regions,namely the fine zone,coarse zone,and heat-affected zone.The Si phase is uniformly embedded inα-Al matrix in a network structure.Through fracture morphology analysis,it is found that the fatigue cracks of SLM AlSi7Mg specimens are initiated at the defects such as pores and inclusion,and propagate radially in a semicircle manner.When the remaining section cannot bear the fatigue load,the samples fracture instantaneously,and the fracture zone has the morphology characteristics of cleavage surface and dimple.Comparing the as-built specimens of SLM AlSi7Mg and SLM AlSi10Mg,it is found that the macroscopic differences between the tensile properties and fatigue properties of the two specimens are currently small.The microstructure of specimens formed by SLM is similar and contains a large number of scattered defects.