【摘要】 考察了Sr、Sr+B对近共晶Al-11.6%Si-0.4%Mg合金组织与力学性能的影响,并测定了T6状态下枝晶α相的显微硬度。Sr变质处理可增加组织中枝晶α相的数量,初晶α相呈细长的高度分枝的柱状枝晶,可显著改善合金的力学性能,特别是塑韧性。T6状态下,枝晶α相的显微硬度先随Sr量的增加而增加,在0.025%Sr处达到峰值,随后下降。在Sr变质的合金中加入B,细长的柱状枝晶转变成等轴枝晶;随着合金中B量增多,枝晶团尺寸显著减小,T6状态下枝晶α相的显微硬度增加。对于近共晶Al-Si-Mg合金,Sr变质+B细化联合熔体处理是非常必要的,可同时显著提高合金的抗拉强度和伸长率。更多还原

【Abstract】 Influences of Sr-modification and combination of Sr-modification and B-refinement on the microstructures and mechanical properties of near eutectic Al-11.6%Si-0.4%Mg casting alloys were investigated, and micro-hardness of the dendritic α phase after T6 temper was measured. Sr-modification could increase the amount of the dendritic α phase, which was present as fine and slender columnar dendrites. And the mechanical properties, especially the ductile, of as-cast samples and that after T6 temper, increased considerably with the increase of Sr content in the alloy. With increase of Sr content in the alloy, the micro-hardness of the dendritic α phase after T6 temper increased first, maximized at 0.025%Sr and then decreased. Addition of B in the 0.030%Sr modified alloy resulted in a transition of primary α phase from fine and slender columnar dendrites to fine equaixed dendrites. With increase of B content in the alloy modified with strontium, the size of the dendrite cells decreased remarkably and the micro-hardness of the dendritic α phase after T6 temper increased. For the near eutectic Al-Si-Mg alloy, the combination of Sr-modification and B-refinement was very necessary in practice and it could simultaneously increase the ultimate tensile strength and elongation.更多还原