铝粉粒径和热压温度对15%SiC/2009Al复合材料力学性能的影响

Effect of Aluminum Powder Size and Temperature on Mechanical Properties of Hot Pressed 15%SiC/2009Al Composite

将不同粒径(13μm和32μm)的Al粉在不同温度用粉末冶金加热挤压工艺制备出复合材料15%SiC/2009A1,用光学显微镜(OM)、扫描电镜(SEM)、电子探针(EPMA)和电子万能试验机对其表征,研究了Al粉的粒径对其微观组织和力学性能的影响。结果表明,用小粒径Al粉在任一温度热压制备的复合材料其强塑性都优于用大粒径Al粉的材料。其原因有:一,大粒径Al粉使SiC颗粒分布不均匀;二,在用大粒径Al粉制备的复合材料中Cu、Mg元素扩散不均匀,与引入的Fe、O元素生成大尺寸难溶相;三,用大粒径Al粉制备的复合材料中SiC颗粒与铝基体的界面结合较弱(尤其是热压温度较低时),在拉伸变形过程中大量SiC颗粒与铝基体脱粘。用两种粒径Al粉制备的复合材料,随着热压温度的变化其断裂方式不同。用小粒径Al粉在不同温度热压制备的复合材料,其断裂方式均为铝基体的韧性撕裂和SiC颗粒断裂。用大粒径Al粉制备的复合材料低温热压时其断裂方式为SiC-Al界面脱粘,热压温度提高可改善界面结合,使断裂方式变为铝基体的韧性撕裂和SiC颗粒断裂。热压温度为580℃用两种粒径Al粉制备的复合材料力学性能最佳,尤其是用小粒径Al粉制备的材料其抗拉强度、屈服强度分别达到556 MPa、381 MPa,延伸率达到9.2%。

Hot pressed Al-based composites of 15%SiC/2009A1(volume fraction)were prepared by powder metallurgy method.The effect of the variation of Al powder sizes(13μm,32μm)and temperatures(560oC,580oC,600oC)on their microstructure and mechanical property was studied using optical microscopy(OM),scanning electron microscopy(SEM),electron probe microanalysis(EPMA)and tensile tests.The results show that the composite prepared with small Al powders has higher strength and ductility than that prepared with large Al powders.The reason could be attributed to the following three aspects.First,large Al powders result in the uneven distribution of SiC particles in the matrix.Secondly,in the composites prepared with large Al powders,Cu and Mg spread unevenly and which then react with the extrinsic contaminants such as Fe and O,forming large-sized insoluble phases.Thirdly,in the composite prepared with large Al powders,the bonding between SiC particles and the aluminum matrix is weak,which is particularly obvious when the hot pressing temperature is low,resulting in debonding of SiC-Al interface during tensile tests.The fracture mechanism of the composites prepared with the two Al powders was analyzed.At all hot-pressing temperatures,the composites prepared with small Al powders are fractured due to the tearing of the Al-matrix and fracture of SiC partculates.However,for the composite prepared with large Al powders,SiC particles and aluminum matrix tend to debond when hot pressing at low temperature,while the interfacial bonding is improved with the increase of hot pressing temperature.When hot pressing at 580oC,the mechanical properties of the composites are the best,especially for that withsmall Al powders.Correspondingly,the tensile strength and yield strength reach 556 MPa and 381 MPa respectively,and the elongation reaches 9.2%.