楔压加工对Al-20Si合金铸造管坯组织性能的影响

Effects of Microstructures and Mechanical Properties of Casting Al-20Si Alloy Pipe During Wedge Pressing

为了消除铸造铝硅合金中的孔洞、疏松等缺陷,改善合金组织,提高合金性能,采用基于多道次局部小变形累积致整体成型的楔形压制工艺,对通过重力铸造方法制备出直径为Ф328mm的Al-Si管坯,进行楔形压制.通过金相组织、室温拉伸、布氏硬度和SEM等手段,研究了楔形压制的规律及合金的组织与性能的演变.结果表明:管坯中的孔洞显著闭合,材料的有效承载面积增加,粗大的初生硅被破碎变小,初生硅和共晶硅在铝基体上分布更加均匀.当楔形压制的变形程度达到40%时,管坯的力学性能及密度与铸态相比,由σb=112 MPa,δ=1.2%,ρ=2.48 g/cm3分别提高到203 MPa,5.2%及2.68 g/cm3.

In order to eliminate the pores and shrinkage porosity in the casting aluminum silicon alloy,and improve the microstructures and the mechanical properties of the alloy,large size Al-Si alloy pipes were prepared with gravity casting.A new wedge pressing process for compressing large scale porous tubular performances was adopted on the basis of the idea of accumulating local small deformation as to integral forming.The rule of the wedge pressing process and microstructures and the mechanical properties of the alloy were investigated with hardness tests,tensile tests and SEM.The results have shown that the wedge pressing process can markedly eliminate the pores and shrinkage porosity in gravity casting performances.The coarse primary silicon was crushed,and most of the eutectic silicon was refined and distributed uniformly in the matrix.The mechanical properties and density of the gravity casting increased from 112 MPa,1.2% and 2.48g/cm3 to 203 MPa,5.2% and 2.68g/cm3 respectively after the reduction of 40%.