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

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 solidi. cation curve. The characteristic signals for hot tearing were an AE energy of over 600 e.u. and an average frequency of similar to 125 +/- 15 kHz in zone II. For hot cracking, the AE energy was over 650 e.u. and the average frequency was similar to 128 +/- 17 kHz in zone III. The hot-tear start temperature ranged from 636 degrees C to 653 degrees C; the nonequilibrium solidus T's, from 556 degrees C to 614 degrees 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 solidi. cation cracking (E-total) HSC congruent to 167 (E-total)(-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.