(华南理工大学 机械与汽车工程学院,广州 510640)
摘 要: 采用拉伸性能测试、光学显微镜、扫描电镜、透射电镜、电子探针、X射线衍射等研究了T7热处理态的挤压铸造Al-5.0Cu-0.6Mn-1.0Fe-1.0Ni合金的显微组织及力学性能,重点研究了挤压压力对合金高温力学性能的影响。结果表明:当挤压压力从0 MPa增加到75 MPa时,合金的高温力学性能明显提高,但抗拉强度和屈服强度的增加值随温度升高而逐渐减小。挤压压力可以消除合金中的缩松,抑制合金中针状Al7Cu2Fe相的形成,使块状Al7Cu2Fe相及Al9FeNi相分布更为弥散,并形成联通的骨骼状结构。但是,挤压压力也使合金晶间热稳定性好的富铁相数量减少,同时,细化合金晶粒及二次枝晶,增加晶界数量。
关键字: 铝铜合金;挤压铸造;高温;力学性能
(School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China)
Abstract:The microstructures and mechanical properties of the T7 heat-treated Al-5.0Cu-0.6Mn-1.0Fe-1.0Ni alloy prepared by squeeze casting were studied by tensile test, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro analysis (EPMA), X-ray diffraction analysis (XRD). The effect of applied pressure on the elevated temperature mechanical properties of the alloy was investigated mainly. The results show that the mechanical properties of the alloy at elevated temperatures are improved significantly when the applied pressure increases from 0 to 75 MPa. However, the increments of the ultimate tensile strength and yield strength decrease with the increase of the temperature. The applied pressure can eliminate the porosity and suppress the formation of needle-like Al7Cu2Fe phase. Meanwhile, the block-like Al7Cu2Fe and Al9FeNi phases become smaller and more dispersive and form the interconnected bone-like structure. Unfortunately, the applied pressure reduces the volume fraction of the thermo-stable iron-rich phases and it also refines the grain size and secondary dendrite arm space of the alloy, which leads to the increase of grain boundary.
Key words: aluminum-copper alloy; squeeze casting; elevated temperature; mechanical property