OPTIMIZATION OF HOT WORKABILITY OF AN AL-MG-SI ALLOY USING PROCESSINGMAPS

The hot workability of an Al-Mg-Si alloy has been studied by conductin g constant strain-rate compression tests. The temperature range and st rain-rate regime selected for the present study were 300-550 degrees C and 0.001-1 s(-1), respectively. On the basis of true stress data, th e strain-rate sensitivity values were calculated and used for establis hing processing maps following the dynamic materials model. These maps delineate characteristic domains of different dissipative mechanisms. Two domains of dynamic recrystallization (DRX) have been identified w hich are associated with the peak efficiency of power dissipation (34% ) and complete reconstitution of as-cast microstructure. As a result, optimum hot ductility is achieved in the DRX domains. The strain rates at which DRX domains occur are determined by the second-phase particl es such as Mg2Si precipitates and intermetallic compounds. The alloy a lso exhibits microstructural instability in the form of localized plas tic deformation in the temperature range 300-350 degrees C and at stra in rate 1 s(-1).