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熔体过热处理的弛豫过程和引起的不可逆过程使熔体状态变化出现滞后效应,从而影响定向凝固界面形态稳定性.在熔体过热处理后的结构滞后状态下,合金熔体的粘滞性η减小.非平衡溶质分配系数κ增大（在κ0<1的条件下）,同时成分过冷度也趋于增加.当过热处理温度T+低于合金的临界过热温度T+C时,随着T+提高,η值减小和κ值增大,增加了平界面的稳定性;当过热处理温度T+高于合金的临界过热温度T+C时,随着T+提高,成分过冷度有显著增大,又导致了平界面的失稳.
The relaxation process and the irreversible process caused by the melt overheating process cause the hysteresis effect on the melt state, which affects the morphological stability of the solidified interface. Under the structural lag condition after the melt overheat treatment, the viscosity of the alloy melt η decreases, the unbalanced solute partition coefficient κ increases (under the condition of κ0 <1), and the component undercooling also tends to increase.When the overheating temperature T + is lower than the critical overheating temperature T + C, The increase of T +, the decrease of η and the increase of κ value increase the stability of the flat interface. When T + is higher than the critical superheating temperature T + C of the alloy, as the T + increases, the undercooling is significant Increase, but also led to the instability of the flat interface.