Hot tear susceptibility of aluminium–silicon binary alloys

Abstract

Hot tear susceptibility (HTS) of Al–Si alloys in the 0–5–3·0 wt-%Si has been determined using a constrained rod casting test and a quantitative index. Hot tear susceptibility was seen to decrease with increasing silicon content. Hot tear severity varied directly with solidification shrinkageβ, the non-equilibrium freezing range ΔT′, dendrite arm spacing and the effective grain size deff. The highest HTS was seen in the Al–0·5%Si alloy with the largest ΔT′, the highest β, the largest dendrite arm spacing, the lowest amount of eutectic phase feu, and, hence, the longest local freezing time tf. Correlation was observed between HTS and the theoretical hot tear criteria Clyne–Davies CSC, Feurer and Campbell CSCb indices, with Campbell's criterion showing a very strong correlation as HTSc≈0·03CSCb + 6 with R2=0·93, where HTSc is HTS of rod C.