Role of Impurities in Superplastic Flow and Cavitation

小行星9500316 这是细晶材料超塑性流动和空化的基础研究。 主要目的是评估在低应力下的超塑性流动的特性是否是杂质原子在边界处偏析的结果，并解决关于中间应力下的超塑性变形和空化的子结构细节和起源的几个问题。 实验方法包括：（a）深入研究杂质类型和含量对空化过程的影响，（B）表征变形前后杂质在边界上的分布，（c）研究不同形状和尺寸下的空化过程。（c）研究与超塑性变形有关的微观结构细节（边界滑动和迁移、晶粒形状、晶粒旋转、韧带和晶格位错）作为杂质水平和类型、应变和变形的函数，模式（拉伸和双剪切）;和（d）检查的蠕变行为和微观结构的影响，引入氧化物弥散到超塑性合金使用新的工艺反应雾化和沉积。 使用三种不同的模型材料，Zn-22%Al、Pb-62%Sn和Al-33%Cu，并控制杂质量。 %本项目不仅将增进对杂质原子在超塑性合金变形和断裂中作用的理解，而且还将为控制超塑性流动的变形过程的起源提供新的见解。 ***

9500316 Mohamed This is a fundamental investigation of superplastic flow and cavitation in fine-grained materials. The main objective is to assess if the characteristics of superplastic flow at low stresses are a consequence of impurity atom segregation at boundaries and to address several issues regarding the substructure details and origin of superplastic deformation and cavitation at intermediate stresses. The experimental approach involves: (a) an in-depth study of impurity type and level on the cavitation processes; (b) a characterization of impurity distribution at boundaries before and after deformation; (c) an investigation of microstructural details associated with superplastic deformation (boundary sliding and migration, grain shape, grain rotation, ligaments, and lattice dislocations) as a function of impurity level and type, strain, and deformation, mode (tension and double shear); and (d) an examination of the effects on creep behavior and microstructure of introducing oxide dispersoids into a superplastic alloy using the new process of Reactive Atomization and Deposition. Three different model materials, Zn-22%Al, Pb-62%Sn, and Al-33%Cu, are used with controlled amounts of impurities. %%% This project will not only enhance the understanding of the role of impurity atoms in the deformation and fracture of superplastic alloys, but also provide new insights into the origin of deformation processes controlling superplastic flow. ***