在高梯度定向凝固装置中采用枝晶方向与热流偏离的籽晶制备AM3晶体,分析晶体生长过程中杂晶的形核原理和不同晶粒的竞争淘汰机制.结果表明,枝晶方向与热流偏离造成的过冷可促使杂晶的形成.枝晶生长方向与热流偏离较大的晶粒在一定条件下可淘汰枝晶方向与热流接近的晶粒;晶粒的竞争与淘汰过程受晶粒间枝晶的相对位向、晶粒生长方向与热流方向的夹角大小、晶粒的晶体取向等因素有关.
Nickel based superalloy AM3 was prepared in high thermal gradient directional solidification apparatus with a seeding technique. Off-axial seeds were used in the experiments to investigate the nucleation and competitive growth of stray grains. The results indicate that the local undercooling caused by off-axial dendrites could result in stray grains formation. The grains with dendrite direction close to the heat flow direction can be overgrown by those grains which have larger deviation from the heat flow direction. The results reveal that the competitive growth of stray grains depends upon the synthetical effects of the comparative position of the dendrites, the angles between the dendritic direction of the grains and the heat flow direction, and the orientations of the crystal grains.
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