Abstract:

Herein, a hot cracking initiation criterion based on the characteristics of solidification liquid film and the microstructure was proposed, which integrated both the mechanical and non-mechanical factors during solidification. The criterion also took the effect of the shrinkage volume of the solid-liquid two-phase in the mushy zone, the flow behavior of the liquid film and the microstructure on the feeding behavior into account. Meanwhile, the effect factors of hot cracking initiation such as alloy composition, microstructure, mold design and process condition were included in this criterion, and it could quantitatively calculate whether hot cracks occurred under a certain state or not during solidification. The criterion was utilized to predict whether hot cracks occurred in Al-4.0 wt% Cu alloy in different initial solidification states or not, which was consistent with the experimental results and verified its reliability. According to the criterion expression, V_feeding^* was related with five effect factors including η, ΔP^*, l^*, r^* and n, in which r^* and n were in positive correlation with V_feeding^* while η, ΔP^* and l^* were in negative correlation with that, which provided a good instructive significance for mold design, process optimization and composition and microstructure regulation of alloys and simultaneously further enriched the mechanism and influencing factors of hot cracking initiation. Furthermore, a multiscale simulation method for calculating the characteristic parameters of hot tearing behavior during solidification was also provided in this study.

Key words: Hot cracking criterion, Liquid film characteristic, Microstructure, Aluminum alloy, Multiscale simulation