During casting the semi-solid microstructure is frequently subjected to the tensile stresses, which are closely related to cast defects such as hot tearing, porosity and macrosegregation.To examine the micromechanics of semi-solid deformation, a modified experimental set-up is employed in Gleeble 3800 thermomechamical testing unit to achieve a uniform temperature distribution in partially remelted aluminum samples.The temperature variation in the vicinity of the target temperature was markedly reduced to one degree for a length of 4-5 mm in the middle of the tensile samples.