The Study of Hot Deformation Behavior of Mechanically Milled and Hot Extruded Al-BN Nanocomposite

摘要

Hot deformation behavior of mechanically milled and hot extruded Al-BN nanocomposite is investigated by hot compression test in the temperature range of 350-500 A degrees C and strain rate of 0.001-1 s(-1). The plastic flow of the nanocomposite as a function of temperature and strain rate is described using a constitutive equation. Based on dynamic materials model, the processing map is developed at the strain of 0.7 representing stable and instable domains. The stable and instable domains in the processing map are verified by microstructural evaluation using transmission and scanning electron microscopes. The results show that the flow instability domains including micro voids and surface cracks have occurred in the range of: (1) T = 350-380 A degrees C, = 0.001-0.015 s(-1), (2) T = 370-430 A degrees C, = 0.1-1 s(-1), and (3) T = 460-500 A degrees C, = 0.001-0.03 s(-1). The safe and stable domains for hot deformation of nanocomposite have occurred in the range of: (1) T = 350-370 A degrees C, = 0.1-1 s(-1), (2) T = 390-450 A degrees C, = 0.003-0.05 s(-1), and (3) T = 440-500 A degrees C, = 0.1-1 s(-1). Finally, the investigation shows that the best processing parameters for this new nanocomposite are within the temperature range of 390-450 A degrees C and strain rate range of 0.003-0.05 s(-1).