采用真空感应熔炼与等温固溶相结合,研究了稀土Y对铜模喷铸Mg-6Al合金快冷组织形成及其热稳定性的影响。结果表明:非平衡凝固Mg-6Al-1Y合金中形成亚稳稀土Mg 24 Y 5相,能够促进晶粒细化,抑制溶质偏析,形成细小球状晶组织。随铜模内径降...采用真空感应熔炼与等温固溶相结合,研究了稀土Y对铜模喷铸Mg-6Al合金快冷组织形成及其热稳定性的影响。结果表明:非平衡凝固Mg-6Al-1Y合金中形成亚稳稀土Mg 24 Y 5相,能够促进晶粒细化,抑制溶质偏析,形成细小球状晶组织。随铜模内径降低,凝固冷速增加,晶粒细化效果更加显著,其中内径为2 mm时所获得的平均晶粒尺寸减小到2μm以内。Y的加入导致晶界处β相转变温度由425.57℃升高到429.46℃,提高了快冷Mg-6Al合金的高温热稳定性。高冷速引起的细晶强化有利于增加快冷Mg-6Al-1Y合金的显微硬度。经400℃/2 h固溶处理后β相的溶解导致快冷合金硬度下降。展开更多
The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of ...The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of the temperature of the undercooling liquid. If the increment rate of the critical nucleus radius, owing to the heating process, is higher than the growth rate of the nuclei, the nuclei generated at the low temperature will become the embryos at the high temperature. This means that the high heating rate can make no nucleation happen in the heating process. In consideration of the interfacial energy, the growth rate of the nuclei increases with the increase of their size and the growth rate of the critical nucleus is zero. Thus, the lower heating rate can also make the nuclei decline partially. Finally, this theory is used to analyze the nucleation process during laser remelting metallic glass.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50971102)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20116102110016)+1 种基金the National Basic Research Program of China(Grant No.2011CB610402)the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China(Grant No.SKLSP201306)
文摘The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of the temperature of the undercooling liquid. If the increment rate of the critical nucleus radius, owing to the heating process, is higher than the growth rate of the nuclei, the nuclei generated at the low temperature will become the embryos at the high temperature. This means that the high heating rate can make no nucleation happen in the heating process. In consideration of the interfacial energy, the growth rate of the nuclei increases with the increase of their size and the growth rate of the critical nucleus is zero. Thus, the lower heating rate can also make the nuclei decline partially. Finally, this theory is used to analyze the nucleation process during laser remelting metallic glass.
