| High temperature creep behaviour of Al-5 wt.% Mg alloy matrix composite reinforced with 7.5 vol.% BN flakes was studied at temperatures of 300, 330, and 300℃ under the applied stress range of 15-80 ㎫. The composite was manufactured by the pressureless infiltration technique in a nitrogen atmosphere. The composite showed high apparent stress exponent and activation energy. Threshold stress was also shown, which was strongly temperature dependent. True stress exponent of the composite was measured as 5 and true activation energy was found to be 131 KJmol^(-1), which is close to the self-diffusion activation energy of pure Al. The major creep mechanism of the composite was found to be lattice self-diffusion of the matrix alloy. Aluminum nitride(AlN) and other compounds such as AlB₂, which were formed in the matrix during the pressureless infiltration process, seemed to be the cause of the threshold stress and the high creep resistance of the matrix alloy. |
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