Regression analysis of the effect of Ge and Si on the torsional strength and fracture angle of aluminium alloys using one-way ANOVA

INTRODUCTION: Aluminium alloys represent a highly sought-after category of structural materials, ranking just below iron-carbon alloys in their application within the manufacturing sector.  In this study, the effect of germanium as an oxide (GeO2) form and Si, introduced as modifying additives into aluminium casting alloys on their torsional strength was investigated. OBJECTIVES: Aluminium alloys ZL201 and AA5056 were selected as a study objective which are widely used in the production of shaped castings. METHODS: During the study, germanium as an oxide (GeO2) form and silicon were introduced into the composition of selected aluminium alloy grades in various combinations, after which their torsional strength was tested using WP 500 testing equipment. Specimens melted in an induction furnace and cast at 720 °C into sand-clay moulds. The moulds were prepared as standardized specimens. During the study, the torsional failure angle and torsional strength of the aluminium specimens were determined. These parameters were calculated using a computer program linked to the WP 500 testing equipment. The effect of adding germanium and silicon on torsional strength and fracture angle of ZL201 and AA5056 aluminium alloys was investigated. One-way ANOVA was used to verify the reliability of the experimental tests. RESULTS: It was found that the torsional strength of the alloy increased under the influence of germanium and silicon; however, when the germanium content exceeded 2%, the torsional strength of the studied aluminium alloys decreased. Based on the obtained results, graphs of the fracture angle and torsional strength as a function of the germanium and silicon content in the alloy were constructed. CONCLUSION: Obtained results demonstrated that the addition of GeO2 with Si led to significant grain refinement, dispersion of eutectic and intermetallic phases, and improvement in structural homogeneity. The findings highlight the existence of a well-defined optimal Ge% concentration around 2%, at which both frictional and mechanical properties are maximized.