(沈陽工業(yè)大學 材料科學與工程學院，沈陽 110870)
摘 要: 采用熱分析法和鑄造熱裂試驗研究MgZn4.5YxZr0.5(x=0.5，1，2，4，6(質(zhì)量分數(shù), %))合金的熱裂行為。結(jié)果表明：MgZn4.5Y1Zr0.5合金的枝晶干涉溫度Tcoh最高、在脆弱區(qū)域的溫度差ΔTc最大、在最后凝固階段剩余的液相量最少、形成的液膜厚度較薄，補縮程度較低，所能抵御的凝固收縮力最小、裂紋擴展速率最大。這些現(xiàn)象說明MgZn4.5Y1Zr0.5合金具有最高的熱裂敏感性。隨著Y含量的增加，聚集在晶界處的低熔點相對合金熱裂行為的作用以及合金的熱裂形成機制均發(fā)生變化：當Y含量不超過1%時，低熔點相主要對晶間結(jié)合力起破壞作用，合金的熱裂形成機制主要是晶間搭橋的斷裂；當Y含量超過1%時，低熔點相主要對枝晶分離區(qū)起補縮作用，合金的熱裂形成機制為晶間搭橋、枝晶分離區(qū)域的補縮和液膜共同作用。
關(guān)鍵字: Mg-Zn-Y-Zr系合金；凝固參數(shù)；熱裂敏感性
（School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870, China）
Abstract:Thermal analysis method and constrained rod casting (CRC) were used to study hot tearing behavior of MgZn4.5YxZr0.5 (x=0.5, 1, 2, 4, 6 (mass fraction, %)) alloys. The results show that MgZn4.5Y1Zr0.5 alloy possesses the highest hot tearing susceptibility (HTS) among the tested alloys due to the highest coherency temperature (Tcoh), the largest temperature difference (ΔTc) in vulnerable region, the least residual liquid in last stage of solidification, the lowest anti-contraction force of thinner film, the poorer feeding capability and the highest crack propagation rate. The role of low-melting point phases gathering at grain boundary on the HTS and the main mechanism of hot tearing shift gradually with different Y contents: when Y is not more than 1%, the role is mainly a damaging effect on intergranular binding force and the main mechanism is fracture of intergranular bridges; when Y is more than 1%, the role is mainly an intergranular feeding effect on formed separated dendrites and the main mechanism is the collective effect of intergranular bridges, intergranular feeding and film.
Key words: Mg-Zn-Y-Zr alloy; solidification parameter; hot tearing susceptibility
