PROCESSING MAP FOR HOT-WORKING OF AS CAST MAGNESIUM

The constitutive flow behaviour in hot working of as cast magnesium ha s been studied with the help of a processing map developed in the temp erature range 300-550-degrees-C and strain rate range 0.001-100 s-1. T he map, interpreted using the dynamic materials model, revealed that t he material undergoes dynamic recrystallisation at 425-degrees-C and 0 .3 s-1, which are the optimum parameters for hot working. At temperatu res higher than 450-degrees-C and strain rates lower than about 0.1 s- 1, wedge cracking occurs in as cast magnesium. The wedge cracking doma in has a high efficiency of power dissipation (60%), whereas the dynam ic recrystallisation domain has a value of 34%. At temperatures below 450-degrees-C and strain rates above 10 s-1, the material exhibits flo w instability in the form of mechanical twinning. At higher temperatur es and strain rates, instability is manifested by flow localisation.