AXIAL COLD COMPRESSION OF SINTERED AL-4CU DISCPREFORMS AND RING-PREFORMS

Experiments were conducted to evaluate the densification behaviour of sintered Al-4Cu disc- and ring-preforms during axial cold compression under a given set of lubricating conditions and also to establish the effect of initial aspect/geometric ratio on the aforesaid behaviour. D isc- and ring-compacts of different aspect/geometric ratios were prepa red using a 60 tonne capacity UTM. These compacts were then coated wit h an indigenously developed ceramic coating and allowed to dry at room temperature for a period of 6 h. Sintering of these ceramic coated co mpacts was carried out at 823 K for 90 min, followed by cooling in the furnace itself. The cold compression of sintered Al-4Cu disc preforms of three initial aspect (H/D) ratios, namely 0.35, 0.60 and 0.65 and ring preforms of four geometric (OD:ID:H) ratios, namely 6:2:2, 6:2:3, 6:3:2, 6:3:3 was carried out both with and without graphite as a lubr icant. The characteristic nature of the densification curves for both disc- and ring-preforms is similar and conforms to a second-order poly nomial. However, disc- and ring-preforms with lower initial aspect/geo metric ratios exhibited better densification. Further, the densificati on under graphite lubricating condition was inferior, but delayed the appearance of circumferential cracks, which facilitated the achieving of higher densities in the disc- and ring-preforms.