Hot deformation behavior of mechanically alloyed Al6063/0.75Al2O3/0.75Y2O3 nano-composite-A study using constitutive modeling and processing map

The hot deformation behavior of mechanically alloyed (MA'ed) Al6063/0.75Al(2)O(3)/0.75Y(2)O(3) nano-composite was characterized in the temperature and strain rate ranges of 300-500 degrees C and 0.001-1 s(-1) using compression test. Hot workability is interpreted by processing maps based on dynamic material modeling (DMM) and constitutive model was established based on sine-hyperbolic Arrhenius kinetic rate equation. Dynamic recrystallization (DRX) occurs in the temperature range of 400-500 degrees C and strain rate range of 0.001-0.1 s(-1). The optimum processing parameters for hot working of MA'ed Al6063/0.75Al(2)O(3)/0.75Y(2)O(3) nano-composite was identified to be in two domains, viz.: (i) T=395-440 degrees C and (epsilon) over dot = 0.001-0.01 s(-1) and (ii) T=440-500 degrees C and (epsilon) over dot = 0.003-0.01 s(-1) respectively with maximum efficiency of about 37-39% respectively. At strain rates ranging from 0.1 to 1 s(-1) the nano-composite exhibits flow instability for all temperatures investigated. The average apparent activation energy for hot deformation is calculated to be 181 kJ/mol and flow behavior of the material was styled through a constitutive model. The reasons for the flow instability have been observed to be the surface cracking, void formation, matrix cracking, pores and wedge cracking. (C) 2012 Elsevier B.V. All rights reserved.