Aluminum Magnesium Scandium Alloy During Hot Working Process On The Basis Of Research

The Al-Mg-Sc casting alloy prepared by semicontinuous ingot metallurgy method under the conditions of industrial production was studied in the paper. Using thermal simulation, thermoplastic, metallographic analysis and electronic microscopy, thermal processing performance of Al-Mg-Sc casting alloy were investigated. The results show:(1) The flow stress of Al-Mg-Sc alloy increases with the rising ture strain rapidly at first and tends to be constant after a peak value. The flow stress increases with strain rate increasing and decreases with deformation temperature increasing.(2) When Al-Mg-Sc alloy deforming at high temperature, the natural logarithm of strain rate ln(?) and lnσ,ln[sinh(ασ)] , ln[sinh(ασ)] and the reciprocal of tempurture 1/T satisfy linear relationship. That's to say, the deformation process of this alloy is a thermal activation process similar to high-temperature creep process. Thus, the high temperature deformation material constant of this alloy are:The flow stress a, strain rate (?) and temperature T of Al-Mg-Sc alloy under thermal deformation conditions meet the following relationship:(?) = 4.38×10⁹[sinh(0.0126σ)]^4.81exp(-153086/RT)(3) When deforming at about 400℃according to thermal simulation, thermal cracks will not produce on the sample surface in the strain rate range. When thermal deformation temperature was 440℃or 480℃, only in low strain rates, thermal cracks will not produce on the sample surface.(4) At the same temperature strain rate faster, the slower dynamic recovery is. At the same strain rates higher deformation temperature, the faster the dynamic recovery is. Typical subgrain was formed in Al-Mg-Sc alloy at 360℃deformation, and the size of subgrain increases with the rising deformation temperature. When the deformation temperature is to 480℃, it begins to re-crystallization. With the increased strain rate, the size of subgrain decreases.(5) The tensile and yield strength of Al-Mg-Sc alloy decreases with the rise of temperature. Its elongation increases with the rise of temperature.(6) For Al-Mg-Sc alloy, tensile fracture is transgranular under 300℃, morphology gradually changes from transgranular fracture into a fracture appearance with the intergranular above 300℃, and fracture is intergranular in substance above 400℃, at which time, the strength within the grain is higher than that of grain boundaries and tensile deformation occurs priority at the grain boundary region.(7) With the increase of temperature in thermoplastic experiment, the possibility of crack in rolling is bigger. The best thermal processing temperature of Al-Mg-Sc alloy should be in the range of 400℃to 420℃, in which conditions, deformation resistance of alloys are lower and thermoplastic are better without any hot cracks.(8) Under the manufacture conditions, the temperature of hot rolling is 420℃, and the pass and reduction in pass should be controlled strictly. Reduction in pass and rolling speed should not be oversized at the beginning of rolling. And after the displacement is over 25%, the reduction in pass and rolling speed should be enhanced generally to make sure the deformation distributing in the whole workpiece.