Changes in Microstructure and Mechanical Properties during Solid Sintering of Ni-Al Mixed Powder Compact
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Low temperature reactive sintering of Ni–Al mixed powder compact is performed, and the effects of temperature, time and pressure of sintering on the microstructure, density, hardness and ductility of the compact at room temperature are investigated. During sintering, intermetallic phases and pores are formed and grow. The growth of the former increases the hardness of the compact, while the growth of the latter reduces the density. The volume fraction of aluminum phase decreases in accordance with the parabolic law, and the parabolic rate constant is described as<BR><B>k</B>=3000exp(−60400<B>R</B><SUP>−1</SUP><B>T</B><SUP>−1</SUP>)<BR>where <B>R</B> and <B>T</B> are the gas constant and absolute temperature. The ductility of the compact, evaluated by the critical rolling reduction, dramatically increases by short sintering and then gradually decreases with sintering time. The increase in the ductility is caused by the diffusion junction at the interface between powder particles, while the decrease by the formation of intermetallic compound phases at the interface. Application of pressure to the compact during sintering brings about remarkable increase in the density and hardness of the compact.
- MATERIALS TRANSACTIONS
MATERIALS TRANSACTIONS 37(5), 1067-1072, 1996-05
The Japan Institute of Metals