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本文阐述了到目前为止所进行的与 Al-7Si-Mg(重量%)合金的组织和机械性能有关的铸造和热处理参数的研究工作。虽然标准技术推荐有较宽的镁含量范围和相当高的铁含量,但是,为了获得最佳和均匀的机械性能,镁的含量应控制在由要求的性能所决定的上限或者下限附近的一个窄范围之内,而且铁的含量也应较低。一些研究揭示出共晶硅的变质作用略微增加合金的延性和断裂韧性,也有认为在低的铁含量情况下,变质作用效果明显。一般地说,较高的凝固速率可得到较好的机械性能。延迟时效(在沉淀硬化情况下,淬火和人工时效之间停留的时间)严重影响合金的强度。延迟时效机制可用 Pashlcy 的动力学模型解释。已有报道认为,某些微量添加剂(镉、铟、锡等)能抑制延迟时效的不利作用。尤其应注意的是,在任何技术标准中都未提及过延迟时效问题。关于微量添加剂对抑制延迟时效的作用机理提出过各种假说。而杂质——空位交互作用显然得到最广泛的认可。
This paper describes the work done so far on the casting and heat treatment parameters related to the microstructure and mechanical properties of Al-7Si-Mg (wt%) alloys. Although standard techniques recommend a wide range of magnesium contents and a relatively high iron content, the magnesium content should be controlled within a narrow or high limit near the upper or lower limit determined by the required properties in order to achieve the best and uniform mechanical properties Range, but also the content of iron should be lower. Some studies have revealed that the metamorphism of silicon slightly increases the ductility and fracture toughness of the alloy. It is also believed that the effect of metamorphism is evident at low iron contents. In general, higher solidification rates give better mechanical properties. Delayed aging (in the case of precipitation hardening, the time between quenching and artificial aging) seriously affects the strength of the alloy. The delay mechanism can be explained by Pashlcy’s kinetic model. It has been reported that some trace additives (cadmium, indium, tin, etc.) can inhibit the detrimental effects of delayed aging. In particular, it should be noted that there is no mention of delay-aging issues in any of the technical standards. Various hypotheses have been proposed regarding the mechanism of action of trace additives on the inhibition of delayed aging. The impurity-vacancy interaction is obviously the most widely accepted.