Deformation Processing Maps for Control of Microstructure in Al-Cu-Mg Alloys Microalloyed with Sn

High-temperature deformation behaviors of Al-5.9 pct Cu-0.5 pct Mg alloy and Al-5.9 pct Cu-0.5 pct Mg alloy containing 0.06 wt pct Sn were studied by hot compression tests conducted at different temperatures and strain rates. Trace content of Sn resulted in a significant increase of flow stress at various processing conditions. Artificial neural network (ANN) modeling was carried out providing excellent prediction of flow stress at different combinations of strain, strain rate, and temperature. It was possible to predict 100 and 89 pct of the flow stress values of the respective alloys within an error less than +/- 10 pct. The generated flow stress data were used to develop processing maps to delineate the process domains for safe metal working. The power dissipation efficiency maps revealed a maximum efficiency of 60 and 40 pct, respectively, for the base alloy and the microalloyed material. The instability maps generated for the Sn containing alloy revealed only one instability regime. The safe processing zone of the investigated alloys primarily lies at lower regimes of strain rate, which is extended up to higher deformation temperatures, with trace addition of Sn. Optical microscopy characterized these stable regions as dynamic recrystallization (DRX), which resulted in considerable flow softening observed at a low strain rate of 0.001 s(-1). Instability was observed mainly due to shear band formation or intercrystalline cracking.