金属多晶体晶粒长大时晶界的迁移行为

Migration behaviors of boundaries in polycrystalline metals during grain growth process

为克服传统三维多晶体晶粒正常长大基本理论的缺陷,以棱边或角隅迁移带动晶界迁移的方式推导出了新的晶粒长大关系式.以凯尔文十四面体为晶粒的基本形状,分析了多晶体晶粒长大时棱边及角隅密度的变化规律及其对晶粒长大速度和迁移激活焓的影响.以实验Fe-3%Si合金为例,用新关系式对其晶粒长大过程进行了模拟计算.结果显示,棱边或角隅迁移带动晶界迁移所反映出的规律,尤其是角隅迁移,更接近真实晶粒的长大过程,传统关系式中的缺陷得到明显改进,所推算激活焓的变化趋势也与实际观察相符.新关系式尚未能考虑金属三维多晶体中第二相粒子及溶质原子的作用,因此与实际观察结果尚存差异,有待进一步完善.

New equations for grain growth process induced by migration of boundary ligaments and corners were deduced, in order to overcome the shortcoming of the conventional basic theory for normal grain growth in three dimensional polycrystals. The Kelvin＇s 14-sided polyhedron was assumed as basic shape of the grains. The evolutions of ligament density and corner density during grain growth as well as their influences on grain growth rate and migration activation enthalpy were analyzed. The grain growth process of an experimental Fe-3%Si alloy was simulated based on the new equations. It was indicated that the boundary migration driven by motion of ligaments and corners, especially the latter one, comes closer to the real grain growth process, and the shortcoming in conventional equation has been modified obviously. The evolution tendency of activation enthalpy for boundary migration calculated agrees with the actual observations. The new equations did not yet include the effects of second phase particles and solute atoms in three dimensional polycrystalline metals, and therefore could not describe the real process perfectly, which needs to be improved further.