Effect of Solidification Rate and Heat Treating on the Microstructure and Tensile Behavior of an Aluminum-Copper Alloy

An aluminum-copper alloy of the A206 type was melt and cast in molds that promote a thermal gradient during solidification to study the effects that solidification rate exerts on the microstructure of the material. The stress-strain characteristics of heat-treated samples were related to microstructural parameters. The reactions occurring during solidification and cooling were detected and identified by means of thermal analyses. The microstructure of the material was assessed by measuring the secondary dendrite arm spacing, grain size, and porosity. It was found that these parameters increase as the solidification rate decreases. The material was heat treated to T4 and T7 conditions and tested in tension. The stress-strain curves were analyzed to determine the yield and ultimate strengths, as well as the strain to failure and that at which the ultimate strength was achieved. It was found that these properties are enhanced by microstructural refining in either testing condition. It was also found that porosity increased due to dissolution of copper-rich particles during heat treating. The best combination of strength and ductility were achieved in the T4 condition.