An Analytical Model for Prediction of Solidification Cracking Susceptibility in Aluminum Alloys Taking into Account the
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KING during the solidification of an alloy is a serious defect occurring in the final solidification stages.[1,2] Processes involving high solidification rates do not follow equilibrium conditions.[3–5] Among the effects of deviation from the local equilibrium, solute trapping and interface undercooling below the equilibrium temperature can be mentioned.[6,7] As the solidification rate increases, the equilibrium partition coefficient has no longer time enough to draw back the atoms of the solute element into the liquid at the interface tip to maintain the local equilibrium.[8,9] As the growth rate accelerates, the partition coefficient, the
ZEINAB MALEKSHAHI BEIRANVAND, FARSHID MALEK GHAINI, and HOMAM NAFFAKH MOOSAVY are with the Materials Science and Engineering, Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran. Contact email: [email protected] MOHSEN SHEIKHI is with the Materials Science and Engineering, Department of Materials Engineering, Bu-Ali Sina University, Hamedan, Iran. MOHAMMAD JAVAD TORKAMANY is with the Laser Material Processing Group, Iranian National Center for Laser Science and Technology, Tehran, Iran. Manuscript submitted August 27, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
liquidus slope, the cell/dendrite tip radius, and the liquid composition in the cell/dendrite tip increase steadily from their equilibrium values.[8] In pulsed laser welding, rapid solidification conditions are created. It has been shown that the partition coefficient increases in the pulsed laser melting experiment (PLM) with the enhancing growth rate.[9] A solidification rate above 0.01 m/s is usually considered rapid solidification.[10,11] Several models have been proposed to describe the dependence of the partition coefficient on the solidification rates, including the Aziz model (CGM model) in 1982, with widely acceptable continuous growth.[10] In 2013, Galenko–Sobolev (LNDM model) improved the Aziz model by introducing the diffusive speed of the solute elements into the liquid bulk under local nonequilibrium conditions.[7,9] Experimental investigations have shown that maximum cracking susceptibility in the casting and laser welding do not occur at the same composition. The maximum cracking susceptibility in laser welding, in comparison with casting, increases.[12] Li showed that the maximum cracking susceptibility occurred in the casting of an Al-Mg alloy in the composition of about 1 wt pct Mg,[13] while other experiments have shown that the maximum cracking susceptibility of the Al-Mg alloy in the laser welding was about 2 wt pct Mg.[14] Some other researchers have shown that the maximum cracking susceptibility occurred in the casting process of
Al-Cu alloys at the composition of about 1.2 wt pct Cu,[15] while Michaud et al. showed that the maximum cracking susceptibility of the Al-Cu alloy in the pulsed laser welding occurred at the composition of about 3.7 wt pct Cu.[16] In 2015, Liu and Kou,[17,18] as well as Sheikhi et al.,[1] each provided criteria based on assuming local equilibrium at th
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