SUPERCOOLING INVESTIGATION AND CRITICAL COOLING RATE FOR GLASS FORMATION IN Pd-Cu-Ni-P ALLOY

摘要

Based on the previous results of undercooling investigation, the critical cooling rate for glass for- mation (R_c) and crystallization behavior of the Pd_4oCu_30Ni_10P_20 alloy are determined and compared with theoretical calculation results using-the classical nucleation theory (CNT). As nucleating homogeneously, the R_c is evaluated to be 2.08 ×10~(-5) K/s under continuous cooling, which is underestimated by four orders of magnitude against the experimental results. Actual crystallization of the alloy is dominated by a hetero- geneous nucleation mechanism. Considering foreign substrate-induced nucleation, the wetting angle (θ) between crystalline embryo and undercooled melt is evaluated to be about 62.5°Furthermore, other het- erogeneous nucleation mechanisms beyond the CNT are discussed to fit the experimental results.