EXPERIMENTAL INVESTIGATION OF STRAIN HARDENING BEHAVIOUR OF SINTERED ALUMINIUM PREFORMS

摘要

Cold upset - forming, densification and strain hardening behaviour of sintered aluminium preforms were investigated. Cylindrical preforms of four initial theoretical densities 82, 86, 89 and 92 percent with aspect ratio 0.75, were prepared using a suitable die, a punch and a die bottom insert on a 1.0 MN capacity hydraulic testing machine. The instantaneous strain hardening exponent n_i. and strength coefficient k_i of the aluminium preforms were calculated and found to have reached the peak value when the deformation or packing density was at low value. Further, it has been observed that the value of n_i and k_i decreased and settled to a constant value for both of the fractional densities of the preforms tested irrespective of the lubricant.