Abstract

A statistical study has been made on the isothermal treatments of A356.0-type Al-Si-Mg alloy. The reprocessed alloy was subjected to hardness evaluation. The values obtained were processed using statistical package for social scientists (SPSS) software to compare all tempers and multiple-step thermal ageing treatment (MSTAT) values by analysis of variance (ANOVA) and Pearson Correlation Index. Equally, a non-parametric and parametric statistics consisting of sign test and t- test respectively were employed for further evaluation of results. This indicate that up to 47% (obtained from the adjusted R square) of the variation in hardness is explained by ageing time. From the statistical analysis of the reprocessed alloy, it was evidenced using one-way ANOVA that all the temper conditions and MSTAT showed six hardness values that have been computed with their corresponding mean and standard error bars. Most of the treatments conducted indicate a significant improvement in the hardness value of the alloy. The Post Hoc Test using the Pearson Correlation Index for all the ageing temperatures and time has been compared. A regression line analysis was also used to compare tempers. The results obtained from these statistical evaluations indicate positive correlations between all the groups of treatments considered in this work.

Key words: Significant level, ANOVA, statistical evaluation, reprocessed alloy.