基板预热温度对选区激光熔化AlSi9Mg1ScZr微观组织及力学性能的影响

Effect of Substrate Preheating Temperature on Microstructure and Mechanical Properties of AlSi9Mg1ScZr Alloy Produced by Selective Laser Melting

摘要:

本文研究了基板预热温度对选区激光熔化制备AlSi9Mg1ScZr合金样品微观组织及力学性能的影响,在35℃、85℃、135℃三种不同基板预热温度下,制备了SLM样品并分别进行微观组织观察及性能测试。结果表明,基板预热温度设置为135℃时,由于基板预热温度和激光扫描热输入的共同影响,使合金在打印过程产生了原位时效效应,在保留细小枝晶和Si网格的同时促进了元素从过饱和固溶体中析出。相比基板预热35℃的样品,纳米尺度的Mg2Si相和Si相在α-Al基体及枝晶界析出的数量显著增加,起到了提高强度的作用；但微米尺度富Fe相的析出对塑性产生了负面影响。在基板预热温度设置为135℃时,制备的AlSi9Mg1ScZr合金在0°方向上屈服强度高达360 MPa、抗拉强度高达502 MPa、伸长率为7%；90°方向上屈服强度高达331 MPa、抗拉强度高达511 MPa、伸长率为5.4%。本研究通过提高基板预热温度,在SLM过程中实现了SLM样品的原位时效,改善了SLM制备AlSi9Mg1ScZr合金的微观组织,在不经过后续热处理的情况下,大幅降低了残余应力,得到了超高强度的AlSi9Mg1ScZr合金样品。

Abstract:

In this paper, the effects of substrate preheating temperature on the microstructure and mechanical properties of AlSi9Mg1ScZr alloy samples prepared by selective laser melting were investigated. SLM samples were prepared at three different substrate preheating temperatures of 35°C, 85°C and 135°C and subjected to microstructure observation and property testing, respectively. The results showed that the substrate preheating temperature set to 135℃ caused the in-situ aging effect of the alloy during the printing process due to the combined effect of the substrate preheating temperature and laser scanning heat input, which promoted the precipitation of elements from the supersaturated solid solution while retaining fine dendrites and Si lattices. Compared to the sample with the substrate preheated at 35 °C, the nanoscale Mg₂Si and Si phases precipitated significantly more in the α-Al matrix and dendrite boundaries, which served to improve the strength; however, the precipitation of the micron-scale Fe-rich phase had a negative effect on plasticity. At a substrate preheating temperature setting of 135°C, the prepared AlSi9Mg1ScZr alloy exhibited a yield strength of 360 MPa, a tensile strength of 502 MPa, and an elongation of 7% in the 0° direction, and a yield strength of 331 MPa, a tensile strength of 511 MPa, and an elongation of 5.4% in the 90° direction. In this study, the microstructure of AlSi9Mg1ScZr alloy prepared by SLM was improved by increasing the substrate preheating temperature and achieving in situ aging of the SLM samples during SLM, which significantly reduced the residual stresses and obtained ultra-high strength AlSi9Mg1ScZr alloy samples without subsequent heat treatment .