搅拌摩擦加工对Al-Si-Fe合金组织和性能的影响

为改善再生铝中富铁相形态,提高其合金性能,本文采用搅拌摩擦加工对Al-Si-Fe合金进行了研究。利用金相显微镜、扫描电镜、万能拉伸试验机、显微硬度计及图形分析仪等研究了加工速度对Al-Si-Fe合金组织和性能的影响。研究结果表明:搅拌摩擦加工后,第二相形态由针状、棒状向细小且均匀分布的球状、粒状和短棒状转变,前进侧热机械影响区组织得到一定程度的细化且具有明显的取向,而返回侧热机械影响区的组织则保持铸态形貌特征的组成。加工中心区的富铁相和共晶硅平均长度较基材分别降低了86.5%、37.4%,而圆整度则分别提高了7.8倍和2.1倍以上,富铁相细化效果优于共晶硅;随着加工速度的提高,富铁相的平均长度逐渐增大,而圆整度则逐渐降低;但加工速度对共晶硅的平均长度影响较小,但圆整度逐渐降低。加工区的抗拉强度、屈服强度大幅降低,最高降幅达55.4%,而伸长率最大可提高6.8倍。随着加工速度的提高,其抗拉强度、屈服强度有所提高,伸长率则逐渐降低,最大降幅达到19.3%。搅拌摩擦加工后,Al-Si-Fe合金晶粒细化,材料性能提升。

Effect of friction stir processing on microstructure and properties of Al-Si-Fe alloy

To improve the morphologies of iron-rich phase in recycled aluminium and the properties of the alloy,microstructure and properties of Al-Si-Fe alloy prepared by friction stir processing(FSP) were investigated. Effects of friction stir processing speed on the morphologies of iron-rich phase and properties in recycled aluminum were studied by using microscope, scanning electron microscope, universal tensile testing machine, micro hardness tester and graphic analyzer. The results show that the morphologies of second phase transform from needle-like and rod-shaped to spherical, granular and short rods with small size and evenly distribution after friction stir processing. The microstructure of thermo-mechanical affected zone at advancing side is refined to a certain extent and has obvious distribution orientation,while thermo-mechanically affected zone at returning side maintains as-cast topography. The average length of iron-rich phase and eutectic silicon in the central region is 86.5% and 37.4% lower than those of substrate, respectively, while the roundness is increased by 7.8 times and 2.1 times, respectively. So the refinement effect of iron-rich phase is better than that of eutectic silicon. As the processing speed increases, the average length of iron-rich phase increases gradually, while roundness decreases gradually. But the processing speed has little effect on the average length of eutectic silicon, while roundness gradually decreases. The tensile strength and yield strength of processing zone are greatly reduced by a highest drop of 55.4%, while elongation is improved by 6.8 times. As the processing speed increases, the tensile strength and yield strength increase lightly, while elongation decreases gradually by the maximum drop reaching 19.3%. The grain size of Al-Si-Fe alloy is refined and the material properties are improved by friction stir processing.