冷却速率对Zn-22%Al合金组织和性能的影响

Effect of Cooling Rate on the Microstructures and Mechanical Properties of Zn-22%Al Alloys

研究了冷却速率对Zn-22%Al合金组织和性能的影响。采用纯氩气保护感应熔炼炉制备了母合金,采用铜模喷铸法和熔体急冷法分别制备了5 mm圆柱样品和条带样品。通过X射线衍射分析表明,合金相主要由富铝相α和富锌相η组成,冷却速率没有改变合金的相组成,但随着冷却速率的增加,富铝相对应的晶面间距及晶格常数增大。冷却速率明显改变了合金的组织形态,母合金样品呈蠕虫状分布,圆柱样品呈树枝状和花朵状分布,条带样品呈等轴晶状分布,组织更加细小,很难区分富铝相α和富锌相η。在细晶强化和固溶强化的作用下,Zn-22%Al合金的显微硬度随着冷却速度的增加而增大。

Effects of cooling rate on the solidified microstructures and mechanical properties of Zn-22%Al alloys were studied. The master alloy was prepared by argon induction melting furnace. The 5 mm cylinder sample and ribbon sample were prepared by copper mould casting and melt spinning, respectively. The phases were investigated by X-ray diffraction. All the alloys are composed of α and η phases. The variation of cooling rates does not change the phase composition of alloys. With the increase of the cooling rates, the interplanar spacing and lattice parameter of α phase increase remarkably. The microstructures of the alloys changed with the change of cooling rate. The microstructure of master alloy showed vermiform, and the microstructure of the cylinder sample showed chrysanthemum-like and dendrite. The microstructure of the ribbon sample presents equiaxed crystals. The grain size is smaller than other samples. The microhardness of the ribbon alloys increases due to the grain strengthening and solid solution strengthening.