Hot deformation behaviour of aluminium alloy 6061/SiC_pMMCs made by powder metallurgy route

Abstract

The hot deformation behaviour of a 20 vol.-%SiC particle reinforced Al alloy 6061 composite and Al alloy 6061, made via a powder metallurgy (PM) route and treated by a T4 temper, were studied by compression testing over a range of temperatures (300 ± 500³C) and at strain rates of 0 . 005, 0 . 05, and 0 . 09 s 21 . It was observed that the ¯ow stresses of the composites were signi®cantly higher than those of the alloy at lower deformation temperatures. However, the stress ± strain curves of both the composite and the alloy showed signi®cant softening during deformation at the lowest strain rate, the softening for the composite being faster than that of the alloy. The activation energy for hot deformation was determined for different strains, using a power law equation, and was found to change signi®cantly with strain for both the alloy and the composite. This phenomenon was explained by the occurrence of dynamic precipitation and coarsening during deformation.MST/4641

Effect of the heat treatment on the hot deformation behaviour of AA6082 alloy

“…This result agrees with that presented in the other papers [3][4][5][6][7][8][9][10][11][12][13][14][15]. It has been shown in several papers, that the flow softening of precipitation hardened aluminium alloys in the supersaturated condition during hot deformation was attributed to the occurrence of dynamic precipitation followed by coarsening [3,10,11,15,16]. The present experimental results can also be explained by the same hypothesis.…”

“…On the other hand, for the tempered alloy, due to dynamic precipitation and coarsening during deformation, Q varies significantly with strain. Zhang et al [15] have checked the variation of activation energy with strain for the AA6061 alloy and SiCp/AA6061 composite following a T4 temper and also found that Q changed significantly with strain due to dynamic precipitation and coarsening during deformation [15].…”

“…The results were used to compare with the calculated temperature increases due to adiabatic heating. Load-displacement data were converted into true stress-true plastic strain curves and corrected for friction and temperature changes using the method in previous paper [15].…”

“…The activation energy can be estimated from the slope (K) of ln σ versus 1/T plots by the relationship Q = KR/m. K, which is the slope of ln σ versus 1/T plots, was calculated at various strains, using the method given in a previous paper [15]. Using the values of m in Fig.…”

“…For some aluminium alloys, work softening occurs during hot deformation [4][5][6]11], and therefore it is necessary to establish constitutive equations that contain parameters as a function of strain [13][14][15].…”