Investigating the Hot Tear Formation in Eutectic Al-Fe Alloys in ‎Mushy ‎Temperatures Ranges by Simulation of Solidification

In the present study, solidification process of Al-Fe eutectic alloys at a metallic mold was done by finite difference method; and the hot tearing sensitivity was investigated. The mold was designed for directional solidification toward the mold center. The results of simulation revealed that the solidification was done in two stages. In the first stage, the mushy zone thickness was increased and in the second stage it was decreased. As the Fe content was increased, the time of first stage was decreased while the time of second one was independent of Fe amounts. In this work, it was supposed that the hot tear is formed only in a pero-eutectic continuous solid network, so, a criterion for hot tearing susceptibility was introduced based on the mushy zone thickness and local solidification time. In this criterion, the hot tears filled with eutectic melt were account as healed hot tears. The results depicted that all alloys could be sensitive to hot tearing during first stage. Because of low cooling rate during the second stage, the melt experiences near equilibrium solidification; therefore the pero-eutectic solid network could not be formed in Al-1.5wt% alloy and consequently this alloy was not sensitive to hot tear. The most sensitivity was related to Al-1wt%Fe and Al-1.5wt%Fe alloys. At the second stage of solidification, the most sensitivity was related to Al-1wt%Fe alloy.