Effect of Ti Addition on the Hot-Tearing Susceptibility of the AlSi5Cu2Mg Alloy

Abstract

The aluminum alloy AlSi5Cu2Mg finds application in the production of high-stress cylinder head castings. The AlSi5Cu2Mg alloy is specific for its high susceptibility to hot tearing. One effective way to reduce the susceptibility of Al-Si-Cu-Mg alloys to hot tearing is by grain refining. The AlSi5Cu2Mg alloy is designed with a specific chemical composition that significantly limits the Ti content to a maximum of 0.03 wt.%. This limitation practically limits the use of standard Al-Ti-B-based refiners. The present work focuses on the investigation of the influence of graded Ti addition on the susceptibility of the AlSi5Cu2Mg alloy to hot tearing. The Ti addition was deliberately chosen beyond the manufacturer’s recommendation (0.1, 0.2, 0.3 wt.%). The solidification process of the experimental alloys with Ti addition was evaluated in this research. On the basis of the thermal analysis, it was shown that due to the addition of Ti, the solidification interval of the AlSi5Cu2Mg alloy increases. An increase in the solidification interval is often associated with an increase in the susceptibility to tearing. The susceptibility of the experimental alloys to hot tearing was evaluated qualitatively and quantitatively. Based on the quantitative and qualitative evaluation, it was shown that the addition of Ti reduces the susceptibility of the AlSi5Cu2Mg alloy to hot tearing. A positive refining effect of Ti on the primary α-(Al) phase was demonstrated by microstructural evaluation. Based on this research, it was shown that despite the increase in the solidification interval due to the addition of Ti, the susceptibility of the aluminum alloy to the formation of hot tears is reduced due to the better filling of the material in the interdendritic spaces.