落管中Pd_(77.5)Au_6Si_(16.5)合金的固化动力学亚稳相的形成

PHASE FORMATION IN DROP TUBE PROCESSING FROM UNDERCOOLED Pd_(77.5)Au_6Si_(16.5) MELT

研究了落管中Pd_(77.5)Au_6Si_(16.5)合金的过冷、生核及亚稳相的形成。在小于400μm的金属小球中发现Pd的固溶体相;在较大的金属小球中则观察到Pd_3Si金属间化合物相。本文还在经典生核理论的基础上,计算了不同相的固液自由能差、成核功、生核速率及晶体生长速度随温度的变化关系,并由此得到时间-温度-转变曲线(t-T-t),计算与实验结果较为一致。

The Pd77.5 Au6 Si16.5 alloy was studied by means of a drop tube processing. Pd solid solution phase was found in smaller droplets (diameter D<400 μm). In larger droplets, the in-termetallic compound PdsSi was observed. The difference of free energy between underco-oled liquid and solid state, the activation energy for the formation of postcritical nuclei, tie nucleation rate and the speed of crystal growth were calculated as a function of temperature for Pd solid solution and PdsSi phases, these calculations led to time-temperature-transforma-tion curves which may be used to describe the experimental findings oa the kinetics of solidification of this alloy.