Evaluation of microstructural evolution of Mg–4Al–xRE in SIMA process based on statistical approach

Abstract

Strain induced melt activation (SIMA) for achieving as nearly as possible a spheroidal semisolid structure with minimum entrapped second phase is more practically/economically advantageous compared to other techniques. One prerequisite towards arriving at an effective SIMA process is the use of appropriate methodology for the evaluation/prediction of pertinent factors in such processes. In the present work, the effects of alloying element, induced strain and holding time on three responses, namely, shape factor, particle size diameter and fraction of liquid, were investigated using response surface methodology based on a central composite design. According to statistical analysis and the developed polynomial equation models, it was found that all the first order terms of the independent parameters as well as second order term of alloying element are statistically significant for all the responses. In the case of shape factor, the second order term of time and the interactive term of induced strain and alloying element have statistical significance.

Keywords:

• Strain induced melt activation
• Response surface methodology
• Magnesium alloy
• Rare earth

Acknowledgement

This experimental research was carried out at Sharif University of Technology, and one of the authors would like to thank Professor H. Ashuri for his valuable and helpful discussions.