Ni_（78.6）Si_（21.4）合金的深过冷与凝固组织演化

深过冷技术研究是凝固科学中重要的研究领域之一.文中采用玻璃熔融净化与循环过热法使Ni78.6Si21.4合金获得了318K的过冷度,研究了其凝固组织随初始过冷度（ΔT）的演化规律,并对凝固组织中的亚稳相进行了分析.研究发现：当ΔT〈193K时,凝固组织为Ni3Si＋（Ni3Si＋α-Ni）非规则共晶;193K〈ΔT〈250K,凝固组织为α？Ni＋（Ni3Si＋α-Ni）非规则共晶;ΔT〉250K时,凝固组织为完全的非规则共晶;随过冷度的增加,过冷合金熔体中依次出现了亚稳相Ni31Si12相和Ni3Si2相.

Solidification Microstructure Evolution of Highly Undercooled Ni78. 6 Si21.4 Alloy

High undercooling technique is one of the important research fields in solidification science. Ni78.6 Si21.4 alloys were undercooled to achieve an undercooling of 318 K with the molten glass denucleation and cycling superheating methods. The solidification microstructure evolution with the initial undercooling （ΔT） and the metastable phase in solidification microstructure were investigated. It is found： When the undercooling is lower than 193 K, solidification structure is composed of primary Ni3Si and （NiaSi＋α-Ni） irregular eutectic; when the undercooling is greater than 193 K but lower than 250 K, solidification structure is composed of primary a-Ni and （Ni3Si＋α-Ni） irregular eutectic; when the undercooling is greater than 250 K, solidification structure is complete irregular eutectic. With the increase of undercooling, the metastahle phases （Ni31Sil2 and Ni3 Si2） were formed in the undercooled melt.