TWI

An experimental investigation is presented into the precipitation and hardening mechanism during FSW (friction stir welding) of Ni model alloys (Ni, 20%Cr, 2%Al, 2%Ti and Ni, 20%Cr, 3%Al, 3%Ti) in which Al and Ti contents were varied to control the degree of supersaturation. Slice specimens (thickness 12.5 mm) were prepared from cast ingots and subjected to annealing and ageing heat treatments. Bead-on-plate welds were fabricated by FSW at a travel speed of 12.5 mm/min and a rotation speed of 150 rpm. Gamma precipitate formation in the stir zone, HAZ and TMAZ (thermomechanically affected zone) was examined by SEM, and hardness variations were measured by Vickers microhardness mapping. The relationship between precipitate dissolution and stir zone temperature is discussed.

6th International Symposium, 10-13 Oct 2006, Session 2A: FSW of High Temperature Alloys, Paper 01