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当A356合金流经由底部反向水流冷却的斜板时将发生部分凝固。在板面上将连续形成柱状枝晶。由于强制对流作用,这些枝晶将被剪切成等轴晶并被出口的半固态浆体冲刷。板面冷却速度可为高质量半固态浆体提供需要的凝固过程,而板面长度可提供必需的剪切过程。将半固态浆体在金属模具中冷却以制备具有理想微观组织的半固态锭坯。此外,对半固态铸造锭坯进行热处理以提高表面质量,并对半固态铸造和热处理后锭坯的微观组织进行对比。研究板面长度和板面冷却速度对斜板冷却锭坯凝固过程和显微组织的影响。三种板面长度(200,250,300 mm)分别对应不同传热系数(1000,2000和2500 W/(m2K))。最佳板面长度和相应的传热系数分别为250 mm和2000 W/(m2K),在此条件下,由于没有浆体附着在板面上,锭坯具有细小的球状组织。
Partial solidification will occur when the A356 alloy flows through the swashplate cooled by the bottom reverse flow. Columnar dendrite will be continuously formed on the plate surface. Due to the forced convection, these dendrites will be sheared into equiaxed grains and washed away by the semi-solid slurry at the outlet. Plate cooling rates provide the needed solidification for high quality semi-solid slurries, while the plate length provides the necessary shearing. The semi-solid slurry is cooled in a metal mold to prepare a semi-solid ingot having the desired microstructure. In addition, the semi-solid cast billets were heat-treated to improve the surface quality, and the microstructures of the billets after semi-solid casting and heat treatment were compared. The effect of plate length and plate cooling rate on the solidification process and microstructure of a slab-cooling billet was studied. Three board lengths (200, 250, 300 mm) correspond to different heat transfer coefficients (1000, 2000 and 2500 W / (m2K) respectively). The optimum plate length and the corresponding heat transfer coefficient are 250 mm and 2000 W / (m2K), respectively. Under this condition, the blank has fine spherical structure because no slurry is attached to the plate surface.