Au对Al-1.7Cu合金均匀化的影响

Effect of Au on the homogenization of Al-1.7Cu alloy

分别对Al-1.7Cu和Al-1.7Cu-Au(摩尔分数,%)合金铸锭在530℃/24 h条件下进行均匀化处理,采用X线衍射仪(XRD)、扫描电镜(SEM)、X线能谱仪(EDS)和电子探针(EPMA)等对合金的形貌与结构进行观察与分析,研究微合金化元素Au对该合金均匀化过程的影响以及Au在铸态和均匀化态合金中的存在形式。结果表明:铸态Al-1.7Cu和Al-1.7Cu-Au合金均析出大量Al_2Cu相,但Al-Cu-Au合金还析出一定量的Al-Cu-Au相,该相主要沿晶界分布,其形貌与初生Al_2Cu相明显不同,为白色骨头状组织,化学计量比为Al_2(Cu_(0.5),Au_(0.5))均匀化后初生Al_2Cu相大部分回溶,而Al_2(Cu_(0.5),Au_(0.5))相为难溶相,只发生熔断球化,其中的部分Cu回溶,化学计量配比转变为Al_2(Cu_(0.25),Au_(0.75)):均匀化后Al-Cu合金的Cu完全固溶到Al基体中,而Al-Cu-Au合金中只有约90%的Cu固溶到Al基体中,约10%的Cu仍偏聚在Al_2(Cu_(0.25),Au_(0.75))相中。可见添加微量Au影响Al-Cu合金中Cu原子的扩散和偏聚情况。

Al-1.7Cu and Al-1.7Cu-Au（mole fraction,%） alloys were homogenized at 530 °C for 24 h.The effect of Au on the homogenization of Al-1.7Cu alloys and its forms in casting and homogenization states were investigated by X-ray diffraction（XRD）,scanning electron microscope（SEM）,X-ray energy dispersive spectroscopy（EDS） and electron microprobe（EPMA）.The results show that primary Al2Cu phase precipitates in cast Al-Cu alloy and Al-Cu-Au alloy.In addition,some primary Al-Cu-Au precipitates in cast Al-Cu-Au alloy,distribute along the grain boundary with stoichiometric ratio of Al2（Cu（0.5）,Au（0.5）） and their microstructure is bone-like shape,different from the primary Al2Cu phase.After the homogenization,primary Al2Cu phase in both alloys dissolve significantly,while Al2（Cu（0.5）,Au（0.5）） phase in Al-Cu-Au allloy is just broken and spheroidized,and its stoichiometric ratio changes to Al2（Cu（0.25）,Au（0.75））.As a result,Cu in Al-Cu alloy dissolves into Al-matrix almost completely,while only 90%Cu in Al-Cu-Au ally dissolves into Al-matrix and another 10%Cu segregates in Al2（Cu（0.25）,Au（0.75）） phase.Diffusion and segregation of Cu in Al-Cu alloy can be affected by adding Au.