Recrystallization and Grain Growth Behavior of Alloy 718 Casting during Hot Working

Abstract

Recrystallization and grain growth behavior of alloy 718 casting were investigated to obtain homogeneous microstructure during hot forging. For this purpose, compression tests were carried out for cylindrical specimens at the temperature range of 1000 to 1150°C and the strain rate of 10-1 and 10sec-1. The dynamic recrystallization behavior caused by the hot compression was investigated in terms of the recrystallized area fraction and average grain size. Reheating was followed to the hot compressed samples at the temperature range of 1050 to 1150°C for 100, 600 and 1800sec, and the static recrystallization behavior caused by the reheating was also investigated. As hot deformation temperature increased from 1000 to 1150°C, both the area fraction and average grain size of dynamically recrystallized grains increased. When higher strain rate of 10 sec-1 was used, the area fraction of dynamically recrystallized grains increased substantially, but the average grain size was not affected. When reheating the hot compressed samples at 1050°C for 100, 600 and 1800sec, respectively, microstructural change including grain growth was not noticed. On the other hand, when reheating the samples at higher temperatures, 1100°C and 1150°C, both the area fraction and the average grain size of the statically recrystallized grains increased considerably as the holding time increased from 100 to 1800sec.