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应用铸件在凝固时的倾出方法详细观察了工业纯铝试样中晶区的形成过程。研究结果表明,在低过热度浇注时,游离晶的运动速率和凝固界面生长速率之间的相互作用决定了晶区的形成以及晶粒的尺寸与形状。当游离晶的沉降堆积速率V大于底部凝固层增长速率R时,将形成尺寸、形状都较均匀的等轴晶。当界面生长方向与游离晶游离运动方向一致时,如果界面生长速率R与游离晶垂直于界面方向的运动速率V之差远远大于界面捕获游离晶的临界速率V临,即R—V》V临,被捕获的游离晶将形成尺寸、形状均匀的等轴晶;如果R—V仅稍大于V临,则形成拉长状等转晶;如果R—V小于V临,则形成柱状晶。对游冷等轴晶区的形成也以游离晶的捕获进行了解释。
The pouring out method of castings during solidification was used to observe in detail the formation of crystalline regions in industrial pure aluminum specimens. The results show that the formation of grain boundaries and the size and shape of the grains are determined by the interaction between the rate of free crystal movement and the growth rate of the solidified interface at low superheat casting. When the deposition rate of free crystal deposition rate V is greater than the growth rate of the bottom solidified layer R will form a more uniform size and shape of the equiaxed crystal. When the growth direction of the interface is consistent with the free movement of free crystal, the difference between the interfacial growth rate R and the moving velocity V of the free crystal perpendicular to the interfacial direction is much larger than the critical rate Vmin of the intercalated free crystal, that is, R-V "V Proximally, the trapped free crystals will form equiaxed grains of uniform size and shape; if R-V is only slightly greater than V, then elongated isomorphous crystals will be formed; if R-V is less than V, then columnar crystals will be formed. The formation of a cold equiaxed zone is also explained by the capture of free crystals.