Modeling of the mechanical properties of directionally solidified Al-4.3% Cu alloy using response surface methodology

Abstract

With increasing demand of high strength to low weight ratio materials, aluminum alloys are getting more commercial importance. Investment casting process following by directional solidification has the capability to produce cast parts with minimum or no grain boundary. These cast parts can perform even at elevated temperatures with improved mechanical properties, especially creep. Owing to these embedded capabilities, directional solidification process is preferred over conventional casting procedures for aluminum alloys. Properties of directionally solidified components highly depend on input parameters. This research aimed to develop the mathematical models for the prediction of ultimate tensile strength (UTS), percentage elongation, and hardness of directionally solidified Al-4.3% Cu alloy. A series of experiments were performed to investigate the effects of grain selector parameters including spiral thickness, spiral diameter, spiral pitch, and spiral rotations using Box-Bhenken design. For the adequacy and validity of mathematical models, analysis of variance (ANOVA) and confirmation experiments were performed, respectively. Spiral thickness was observed as most effective parameter affecting UTS, percentage elongation, and hardness followed by spiral pitch and spiral diameter. Microstructural analysis reveals that grain boundaries disappeared at low level spiral thickness and pitch and high level of spiral diameter and rotations. In comparison with base metal, percentage improvement in UTS, percentage elongation, and hardness ranging from 37.5~93.9%, 20.5~81.3%, and 37.6~85.3%, respectively, has been observed. Innovation in this research is the mathematical modeling of mechanical properties for Al-4.3% Cu alloy using directional solidification process.