SUPERPLASTIC BEHAVIOR OF THERMOMECHANICALLY TREATED P M-7091 ALUMINUM-ALLOY/

The superplastic behavior of thermomechanically treated P/M 7091 alumi num alloy was assessed in the temperature range-of 573 to 773 K. The t hermomechanical treatment (TMT) comprised of three steps of solution t reatment, overaging, and warm rolling. There are large eta-phase (MgZn 2) precipitate particles of average size of 1.30 mu m in the overaged condition. The warm-rolled alloy undergoes continuous recrystallizatio n at the test temperatures of 573 and 623 K, exhibiting a maximum tens ile elongation of 450 pct at 573 K and a strain rate of 8 x 10(-5) s(- 1). The precipitate particles play a major role in the process of cont inuous recrystallization. For a given volume fraction of precipitate p articles and constant amount: of warm rolling (in the course of TMT), an optimum precipitate particle size is expected to, maximize the rate of continuous recrystallization and render the finest recrystallized grain size. The warm-rolled alloy undergoes static recrystallization a t temperatures above 673 K. The grain growth accompanying the deformat ion at these test temperatures limits. the tensile ductility to a lowe r value. Irrespective of the test temperature and strain rate, the spe cimens undergo extensive cavitation when deformed at elevated temperat ures.