Effect of post-process and in-process cooling on wide-area stir zone processed via friction stir processing with pin overlapping
Boggaram V. S. Keerthana, M. V. N. V. Satyanarayana, K. Venkateswara Reddy, M. N. S. Shankar
Abstract
Abstract In the current investigation, the influence of post-process and in-process cooling on microstructural, mechanical and electrochemical behavior of wide-area stir zone (WSZ) processed with overlapping friction stir processing (OL-FSP) was studied. The WSZ was successfully prepared in Al5083 aluminum alloy using multi-pass friction stir processing (FSP) with 50% pin overlapping under both cooling conditions. The post-process cooling FSP (PP-FSP) used solid CO 2 as cooling media, whereas the in-process cooling FSP (IP-FSP) used water as cooling media. The microstructural investigations revealed that grain refinement is uniform in each overlapping pass for both cooling conditions. The IP-FSP resulted in better grain refinement than PP-FSP. Three different types of intermetallic particles (needle-shaped Fe-containing, rod-shaped Mg-containing, and very small Mg-containing grain boundary intermetallic particles) were identified in the base alloy and OL-FSP samples. The hardness was observed to be constant across the WSZ due to the uniform grain refinement, and the IP-FSP sample has better hardness and strength than the PP-FSP sample due to the better cooling effect. The elongation followed a similar trend of hardness. The electrochemical findings revealed that the IP-FSP sample has better corrosion resistance than the PP-FSP sample due to the better grain refinement and fine intermetallics.