Large undercoolings up to 395K (0.28TE) are obtained for 15g samples of Ni-32.5%Sn eutectic alloy by superheating the alloy melt to 108-700K above its eutectic temperature and consequently destroying most of the inher...Large undercoolings up to 395K (0.28TE) are obtained for 15g samples of Ni-32.5%Sn eutectic alloy by superheating the alloy melt to 108-700K above its eutectic temperature and consequently destroying most of the inherent heterogeneous nuclei. The recalcscence phenomenon and its dependence on undercooling and on crystal nuclcation and growth, as well as its relationship to solidification microstructures are studied. The crystalli/ation fraction during recalcsccnce is also calculated. Experiments reveal that recalcscence degree increases with undercooling when the latter is below a certain critical value∧Te, but it decreases as undercooling increases above A 7'( (under present conditions∧Te= 245K, i. c. 0.17TE). The greater the recalescencc degree, the larger the proportion of anomalous eutectic in solidified structures. It is inferred that anomalous eutectic is the product of rapid solidification while lamellar eutectic forms at much slower nuclcation rate and growth velocity.展开更多
文摘Large undercoolings up to 395K (0.28TE) are obtained for 15g samples of Ni-32.5%Sn eutectic alloy by superheating the alloy melt to 108-700K above its eutectic temperature and consequently destroying most of the inherent heterogeneous nuclei. The recalcscence phenomenon and its dependence on undercooling and on crystal nuclcation and growth, as well as its relationship to solidification microstructures are studied. The crystalli/ation fraction during recalcsccnce is also calculated. Experiments reveal that recalcscence degree increases with undercooling when the latter is below a certain critical value∧Te, but it decreases as undercooling increases above A 7'( (under present conditions∧Te= 245K, i. c. 0.17TE). The greater the recalescencc degree, the larger the proportion of anomalous eutectic in solidified structures. It is inferred that anomalous eutectic is the product of rapid solidification while lamellar eutectic forms at much slower nuclcation rate and growth velocity.
