In-Situ Investigation of Hot Tearing in Aluminum Alloy AA1050 via Acoustic Emission and Cooling Curve Analysis

Abstract

Hot tearing in the AA1050 alloy was investigated in real time and in situ using acoustic emission (AE) and cooling curve analysis techniques and a ring mold. Activities involving AE have been detected in three zones of the solidification curve. The characteristic signals for hot tearing were an AE energy of over 600 e.u. and an average frequency of ~125 ± 15 kHz in zone II. For hot cracking, the AE energy was over 650 e.u. and the average frequency was ~128 ± 17 kHz in zone III. The hot-tear start temperature ranged from 636 °C to 653 °C; the nonequilibrium solidus T′S, from 556 °C to 614 °C; the fraction solid at hot-tear onset from 0.71 to 0.99; and the Clyne–Davis hot-tear susceptibility coefficient (HSC) from 0.25 to 0.81. The HSC correlated inversely with a total energy of solidification cracking (Etotal) \( {\text{HSC}} \cong 167\left( {E_{\text{total}} } \right)^{ - 0.8}. \) A hot-tear susceptibility factor (HSF) = (pct Fe)·(cooling rate (CR))2 was related to the HSC and T′S as HSC = 0.002 HSF + 0.3 and T′S = −0.3 HSF + 617.