(西安工业大学 材料与化工学院,西安 710021)
摘 要: 对经过T6处理的两种铸造Al-Si合金(Si含量为12%和18%,质量分数)进行不同温度(250、350、450、550 ℃)、时间2 h的热暴露试验。采用表面粗糙度仪、金相显微镜、扫描电子显微镜、专业型同步热分析仪等测试方法相互结合,对两种Al-Si合金在高温热暴露条件下表面状态的变化进行研究。结果表明:Al-x%Si二元合金的粗糙度变化基本遵循Ra, T6>Ra, thermal exposure>Ra, as-cast的规律;随着热暴露温度的升 高,Al-12%Si粗糙度呈现先降低后升高的趋势,Al-18%Si粗糙度呈现不断升高的趋势;合金表面粗糙度的变化与热暴露试验过程中的Al/Si相界开裂和稀土相的析出有关;对比粗糙度及表面微观形貌变化发现:Al-18%Si比Al-12%Si具有更加优良的高温稳定性,即在较低温度下,随着Si含量的增加,Al-x%Si合金发生开裂的趋势逐渐降低。
关键字: Al-Si合金;粗糙度;微观组织;热暴露
(School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an 710021, China)
Abstract:Thermal exposure tests were performed on two cast Al-Si alloys by T6 heat treatment at different temperatures (250, 350, 450 and 550 ℃) for 2 h. The surface roughness tester, metallographic microscope, scanning electron microscope, simultaneous thermal analyzer and other testing methods were used to study the change of the surface state of two Al-Si alloys under high temperature thermal exposure conditions. The results show that the roughness change of Al-x%Si binary alloy basically follows the law of Ra, T6>Ra, thermal exposure> Ra, as-cast; with the increase of thermal exposure temperature, the roughness of Al-12%Si tends to decrease first and then increases, while that of Al-18%Si tends to increase continuously. The change of alloy surface roughness is related to Al/Si phase boundary cracking and precipitation of rare earth phase during thermal exposure test. By comparing the roughness and phase changes, it is found that Al-18%Si has better high temperature stability than Al-12%Si. That is to say, at lower temperature, with the increase of Si content, the tendency of Al-x%Si cracking gradually decreases.
Key words: Al-Si alloys; roughness; microstructure; thermal exposure