往复挤压对A390铝合金力学及热膨胀性能的影响

Effect of reciprocating extrusion on mechanical and thermal expansion properties of A390 aluminium alloy

在380℃下对铸态A390铝合金进行往复挤压工艺实验,并利用金相显微镜、X射线衍射仪、万能拉伸机及热机械分析仪对往复挤压后坯料的显微组织、力学及热物理性能进行测试。结果表明,往复挤压对材料的基体及硅颗粒均有明显的细化作用;随着往复挤压道次的增加,基体晶粒尺寸、微晶尺寸、硅颗粒轴比和等效直径不断减小,位错密度逐渐升高。初晶硅的细化及硅颗粒轴比的降低,有利于抑制微裂纹的产生,提高往复挤压后的力学性能,减小其热膨胀系数。往复挤压变形能显著提升A390铝合金的强度及塑性,经3道次往复挤压后,坯料的抗拉强度由初始态的140 MPa提升至199 MPa,伸长率由1. 9%提升至6. 3%。相对于初始试样,变形后试样的热膨胀系数整体呈增加趋势,但随往复挤压道次的增加而有所降低。

Reciprocating extrusion(RE)processing of as-cast A390 aluminium alloy was studied at 380℃and the microstructure,mechanical and thermophysical properties of blank after RE processing were investigated by optical microscope,X-ray diffraction,universal tensile machine and thermal mechanical analyzer.The results show that the matrix grain and silicon particles are refined obviously by RE processing.With the increase of RE pass,the size of matrix grain and crystallite,the aspect ratio and equivalent diameter of silicon particles decrease continuously,while the dislocation density increases gradually.The refinement of primary silicon and the decrement of the aspect ratio of silicon particles are favorable for inhibiting the generation of microcracks,improving the mechanical properties and reducing the thermal expansion coefficient(CTE).The RE deformation can significantly improve the strength and plasticity of A390 aluminum alloy.The strength and elongation of A390 aluminium alloy processed by three passes increase significantly from 140 MPa and 1.9%to 199 MPa and 6.3%,respectively.Contrasted with the original sample,the CTE of deforamed sample increases generally.While,the CTE decreases with the increase of extrusion pass.