Effect Of Solid Solution Treatment On Semisolid Microstructure Of AM60B Magnesium Alloy And The Determinants In The Coarsening Of Semi-solid Magnesium Alloy

The effects of solution heat treatment on semisolid microstructures of AM60B magnesium alloys with developed and small equiaxed dendrites have been investigated. Simultaneously, the effect factors determing the coarsening of primary particles in semisolid magnesium alloys have also been studied. The results indicate that the primary particles in semisolid AM60B alloy are in irregular morphologies after the developed dendrite alloy is solutionized for less 2h at 415℃while those are in spherical shape after the alloy is solutionized for about 16 h. When the solution time exceeds 60h, the solid particles become irregular again.When the alloy with small equiaxed dendrites is solutionized for 0~4h, the primary particles in the resulting semisolid microstructures are in spheriocal shape. But when the solution time is prolonged to 8h, some wormlike particles appear. As the solution time is within 8~60h, most of the particles are spheroical and wormlike shapes. After the time is increased to 72h, the particles are in wormlike shape.The colescence of primary particles of semisolid AM60B alloy is more obvious then that of AZ91D alloy when the solid fractions of these two alloys are same. For a same alloy, the coalescence possibility decreases as the solid fraction decreases. When the solid fraction is kept a constant, the smaller the primary particles, the larger the coalescence frequency, and the longer the time that the coalescence operates. After 1% Ce-rich RE is added, the Ce atoms agglomerate in the regions among the primary particles and thus prevent the particles from coalescence.