(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 苏州大学 高性能金属结构材料研究院，苏州 215137)
摘 要: 本文研究了在25 ℃和250 ℃条件下不同Cr、Mn质量比Al-0.9Mg-1.1Si合金的组织和力学性能，对铸锭进行550 ℃、10 h均匀化随后进行水淬，再加热到540 ℃条件下进行热压缩变形，随即进行180 ℃、6 h时效处理得到实验样品，分别在25 ℃和250 ℃进行拉伸试验，最后对合金显微组织进行了分析。结果表明：在25 ℃条件下，Cr、Mn质量比为0.1时，屈服强度达到峰值389 MPa；在250 ℃时，Cr、Mn质量比为0.3时，达到峰值293 MPa。选取Cr、Mn质量比为0.3能够使合金高温强度最大，同时室温强度也较高。析出相、织构和小角度晶界都对合金强度产生了不同程度的影响，但是不同温度下三者对强度的影响强弱显示出差异。在25 ℃时，织构对合金强度的影响起主要作用，而在250 ℃时，小角度晶界对合金强度的影响起主要作用。
关键字: Al-Mg-Si合金；力学性能；析出相；织构；小角度晶界
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. High-Performance Metal Structural Materials Research Institute, Soochow University, Suzhou 215137, China）
Abstract:The microstructure and mechanical properties of Al-Mg-Si alloy with different Cr-Mn mass ratios at 25 ℃ and 250 ℃ were studied. The ingot was homogenized at 550 ℃ for 10 h, then water quenched, and deformed by hot compression at 540 ℃. After that, age treatment was carried out at 180 ℃ for 6 h to get ready for the tensile test at 25 ℃ and 250 ℃. Finally, the microstructure of the alloy was analyzed. The results show that the yield strength reaches the peak value of 389 MPa when Cr-Mn mass ratio is 0.1 at 25 ℃. At 250 ℃, the yield strength reaches the peak value of 293 MPa when the ratio is 0.3. The optimal Cr-Mn mass ratio is confirmed to be 0.3, which can maximize the alloy''''s high temperature strength while the room temperature strength can be retained as well. The precipitated phase, texture and low angle grain boundary (LAGB)all have different effects on the strength of the alloy, but shows difference at 25 ℃ and 250 ℃. At 25 ℃, the texture plays a major role in the alloy strength while the effect of LAGB on the alloy strength plays a major role at 250 ℃.
Key words: Al-Mg-Si alloy; mechanical property; precipitation; texture; low angle grain boundary
