Temperature F

400 800

200 1600

i

i

200 400 600 Temperature 11C

800 1000

200 400 600 Temperature 11C

800 1000

Fig. 1 Dilatometer curve of dimensional changes in a copper P/M compact from sintering. The first portion of the curve up to 315 °C (600 °F) is identical to that of a specimen of solid copper and represents the thermal expansion of the metal with increasing temperature. When sintering begins, shrinkage counteracts thermal expansion, and the curve deviates from that for solid copper. As the temperature increases, the rate of shrinkage increases and the compact contracts. Immediately after reaching the maximum sintering temperature of 925 °C (1700 °F), the compact is cooled at the same rate at which it was heated. During cooling, contraction initially is faster than normal thermal contraction. Eventually, the dilatometer curve slope follows normal contraction. Compacts from -74+43 /'m copper powder pressed at 138 MPa (20,000 psi) and heated at a rate of 3.9 °C/min (7 °F/min) to 925 °C (1700 °F) and then cooled at the same rate.

Fig. 2 Shrinkage of copper powder compacts from -74+43 /'m sieve fraction. Compacted at 138 MPa (20,000 psi) and sintered at various temperatures as a function of sintering time
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