Sintering mechanism of Cu-9Al alloy prepared from elemental powders.

The sintering behavior of Cu-9Al alloys prepared from die pressing of elemental powders was investigated. The experimental results and kinetic analysis showed the formation of three consecutive layers of Al 2 Cu, Al 4 Cu 9 , and AlCu phases, with Al 2 Cu appearing first in the initial solid phase sintering stage. A liquid phase formed in the intermediate stage, resulting from the eutectic reaction between Al and Al 2 Cu phases at 500 °C, which is 47 °C lower than the equilibrium reaction temperature. Swelling occurred when the liquid phase infiltrated the gaps between the copper particles, leaving pores at the original sites of Al particles and Al 2 Cu. In the final stage of sintering, the Al-rich phases (Al 2 Cu and AlCu) transformed to Al-poor phases (Al 4 Cu 9 and α-Cu) in the temperature range of 500–565 °C. Al 4 Cu 9 and α-Cu then transformed to AlCu 3 (β) above the eutectoid reaction temperature (565 °C), whereas AlCu 3 transformed to α-Cu and eutectoid phases (α-Cu + Al 4 Cu 9) during cooling. The pure copper transformed to AlCu 3 , and the pore volume decreased at 1000 °C. The microstructure study helps manipulate precisely the sintering process of Cu-Al alloys and optimize the microstructure with a high dimensional accuracy. Image 1 • The microstructure evolution of Cu-Al alloys during sintering were studied. • The swelling mechanism of Cu-Al alloys during sintering were studied. • Three consecutive layers form in the temperature range of 480–500 °C. • Eutectic liquid forms between the Al and Al 2 Cu phases at 500 °C. [ABSTRACT FROM AUTHOR]