Effect of Casting Wall Thickness on the Microstructure and Properties of the ZL205A Alloy

Author of the article:YANG Ling1 , GAO Yanli1,2, HAO Huilin1,2, LIU Chongzheng1,2, PAN Junjie1,2, LIU Shanguang1,2, WANG H

Author's Workplace：1. Beijing Institute of Aeronautical Materials, Beijing 100095, China; 2. Beijing Engineering Research Center for Advanced Aluminum Alloys, Beijing 100095, China

Key Words：ZL205A alloy; wall thickness; cooling rate; heat treatment

Abstract：The effects of different wall thicknesses on the microstructure and mechanical properties of casting ZL205A alloy were studied. The results show that the cooling rate of the ZL205A alloy decreases with increasing casting wall thickness, which leads to an increase in alloy grain size. The ultimate tensile strength and elongation of the as-cast alloy thus decrease with the reduced cooling rate due to the coarsened grain, while the yield strength slightly increases considering the annealing effect. The eutectic structure along the grain boundaries of castings with different cooling rates is almost completely dissolved after solution quenching treatment. When the cooling rates are 7.4 and 2.0 K/s, the density and size of the precipitates in the casting are close to each other. When the cooling rate is 0.5 K/s, the density of the precipitates decreases while the size increases. The ultimate tensile strength, yield strength and elongation of the alloy decrease with the reduced cooling rate. The hole defects of the casting with a cooling rate of 0.5 K/s increase significantly, but the strength does not decrease abruptly.