Microstructure and Mechanical Properties of Product from Extrusion-Consolidated 7075Al Prealloyed Powder.

摘要

Microstructural changes occurring during the extrusion-consolidation of prealloyed 7075stock were investigated and compared with those occurring in the wrought stock (from which the powder was produced) processed in the same manner as the powder. Emphasis is placed on two areas: 1. The effects of processing variables (starting material condition,processing temperature and amount of deformation) on the microstructure of the processed material. 2. Correlation of the product microstructures with product room tensile properties after a final standard T6heat treatment. The microstructure of the extrusion-consolidation powder product differed in several respects from that of the wrought stock product extruded by the same processing conditions. The latter had a uniform microstructure while the former contained a marked inhomogeneity of both the distribution of the precipitate and the size of the substructure or grain structure (from one powder particle to another) and the presence of oxide boundaries on deformed powder particles. The differences are attributed to the following characteristics of the starting materials: 1. The powder consisted of chilled cast particles coated with oxide films and containing elements (such as chromium) in various degrees of super-saturated solution in different particles. 2. The wrought material was homogeneous without any apparent oxide films.