Liquid phase sintering of P/M aluminium alloys: effect of processing conditions

Four commercial aluminium alloy premixed powders (Ecka Alumix 123, 321, 13 and 431) have been sintered in a broad range of experimental conditions in order to establish the optimum processing sintering cycle. Compacts were pressed at 400 MPa reaching a green density (wax weight excluded) of ∼92.5–95%TD, depending on the powder mixture. Sintering under nitrogen was carried out within a temperature range between 550 and 650 °C during 20 min. After determination of the optimum sintering temperature, additional experiments were performed between 0 and 120 min. The heating rate was varied between 5 and 15 °C/min. The influence of sintering atmosphere was also investigated repeating some of these cycles in hydrogen and vacuum. The effect of the sintering conditions (temperature, time and atmosphere) was evaluated by measuring density and hardness. After sintering, some samples were heat-treated using T4 and T6 treatments. SEM was used for the microstructural characterisation of the resulting materials.