Effect of Starting Grain Size on As-Deformed Microstructure in High Temperature Deformation of Alloy 718

Abstract

Two 7 18 alloys with initial grain sizes of 23 and 54 pm were tested in compression over wide ranges of temperatures (850-l 150 C) and strain rates (0.001-25 s-l) to investigate the effect of initial grain size on the flow behavior and. resulting microstructure. The flow behavior was similar in both alloys. Elongated deformed grains were observed in specimens tested at relatively low temperatures, and dynamic recrystallization occurred at high temperatures. Percentages of dynamic recrystallization were measured for partially recrystallized conditions, and the recrystallized grain sizes were compared for the two alloys in completely recrystallized conditions. Despite the different initial grain size, the resulting grain size after dynamic recrystallization at high temperatures is comparable for the two alloys. However, the fine grain 718 alloy exhibited higher temperature for complete recrystallization at low strain rates. Processing conditions to produce uniform fine microstructure are recommended.