Phase transformation and properties of quasicrystal particles/Al matrix composites

摘要

Diffusion controlled phase transformations and tribological properties and hardness of Al 65 Cu 20 Cr 15 quasicrystal particles(QC p)/Al matrix composites have been studied. The mixtures of the quasicrystal particles with volume fractions of 15%, 20%, 25% , 30% and pure Al powder were hot pressed at 600, 650, 700 ℃. During the diffusion controlled phase transformation induced by hot pressing, a simple cubic icosahedric quasicrystal (SIQC) phase transforms into stable Θ phase with the microstructure of monoclinic of Al 13 Cr 2 through a transitional faced cubic icosahedric quasicrystal (FIQC), a decagonal quasicrystal (DQC) and an approximant of decagonal quasicrystal (DA) phases. And G. P. zones and Al Cu precipitates, θ′ Al 2Cu and θ Al 2Cu, are separated out from the Al matrix respectively after hot pressing. The QC p/Al composites have double strengthening effect after hot pressing. One is the strengthening of the particles that reinforce the matrix Al; the other is the dispersion strengthening of the precipitates in the Al matrix. The hardness of the composites increases with increasing volume fraction of quasicrystal particles. The maximum hardness reaches 1 200 MPa, being 4 times that of Al. The frictional coefficient and the wear rate of the QC p/Al are lower than those of Al. In comparison with SiC p/Al matrix composites, QC p/Al composites have higher hardness and lower frictional coefficient.