Influence of weld simulation on the microstructure and fatigue strength of 2195 aluminum-lithium alloy

Microstructure, tensile and fatigue properties of 2195 AI-Li alloy in the T8 temper (as-received alloy) and after weld simulation in Gleeble 1500 to temperatures of 550 degrees C and 600 degrees C were studied. The microstructure of the alloy consisted of a pancake shaped grains with the major strengthening precipitates of T-1 phase. The weld simulation resulted in the dissolution of T1 phase and the formation of G-P zones, delta' particles and dislocations. The higher simulation temperature enhanced the microstructural modification and resulted in larger grain size, more grain boundary precipitates and microcracks or voids. The weld simulation gave rise to a significant decrease in the yield and fatigue strength due to the absence of T1 phase and other microstructural modifications. Fatigue cracks in the base alloy were observed to initiate generally from the specimen surface, and at the interior defects in the weld simulated specimens, especially after the 600 degrees C simulation. Fatigue striations were typical features observed in the base alloy, while cleavage-like cracking occurred in the alloy after weld simulation.