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在高真空度下 ,采用熔融玻璃净化与循环过热相结合的方法 ,在宽的过冷度范围内 ,研究了Cu50 Ni50合金凝固组织形态演化过程。结果表明 ,随着过冷度增大 ,凝固组织发生了 3次转变。其中 ,当 1 2 0K(ΔT 2 ) <ΔT <1 92K(ΔT 3)时 ,凝固组织发生第 2次转变 ,由粒状晶演变为定向生长的深过冷枝晶。通过组织观察和过冷熔体枝晶生长过程的计算发现 ,快速凝固形成的枝晶在再辉和再辉结束后枝晶熟化过程被高度抑制是在该过冷度区间形成定向枝晶的原因。
Under the condition of high degree of vacuum, the morphology evolution of Cu50 Ni50 alloy was studied under the condition of a wide range of undercooling by combining the purification of molten glass and overheating. The results show that with the undercooling increases, the solidification organization has undergone three transformations. When the temperature is 120 K (ΔT 2) <ΔT <1 92K (ΔT 3), the second transformation takes place in the solidified microstructure and changes from granular to deep overcooling dendrite. Through the observation of microstructure and the calculation of the growth process of undercooled melt dendrites, it was found that the dendrite formed by rapid solidification was highly inhibited after the flashback and after flashback, which is the reason for the formation of directional dendrite in the undercooled region .