热处理对汽车用铝合金性能的影响

Effect of Heat Treatment on Properties of Automotive Aluminum Alloy

采用拉伸试验机、金相显微镜、扫描电镜、EDS等手段,分析了具有不同壁厚的Al-Mg-Si挤压型材的晶粒尺寸、不同时效制度下的拉伸力学性能以及拉伸断口形貌。研究结果表明,时效制度为175℃×16 h时,Al-Mg-Si合金强度达到了最大,断后伸长率达到了最低值,之后断后伸长率基本上保持不变;壁厚1 mm型材的粗晶层厚度大于壁厚2 mm和3 mm的粗晶层厚度;欠时效试样主要以韧性断裂方式断裂,峰时效和过时效为韧性-脆性混合断裂方式;欠时效断口韧窝均匀,韧窝深度大于峰时效和过时效,峰时效和过时效的韧窝大小不一;欠时效的塑性也优于峰时效和过时效。EDS分析结果显示Al-Mg-Si合金韧窝底部存在AlMgSi或AlMg第二相粒子,为韧窝的形成源。

In this paper,for Al-Mg-Si extruded profiles,tensile analysis machine,metallographic microscope,scanning electron microscope,EDS and other analytical methods were used to analyze the grain size of different wall thickness surfaces,tensile mechanical properties of different aging systems and tensile fracture morphology. The results show that the aging system is 175 ℃ × 16 h,the strength of Al-Mg-Si alloy reaches the maximum,the elongation after fracture reaches the lowest value,and then the elongation after fracture is basically unchanged. The coarse grain layer thickness of 1 mm wall thickness is larger than that of wall thickness 2 mm and 3 mm. The under-aged sample is mainly fractured by ductile fracture,and the peak-aged and over-aged samples are ductile-brittle hybrid fracture modes. The under-aged samples have uniform fracture dimples,the dimple depth is greater than the peak-aged and over-aged samples,dimple size is different between the peak-aged and over-aged samples,and the plasticity of the underaged sample is better than the peak-aged and over-aged samples. The EDS analysis results show that AlMgSi or AlMg second phase particles exist at the bottom of the Al-Mg-Si alloy dimple,which is the source of the dimple formation.