Phase transformation and properties of quasicrystal
particles/Al matrix composites①
particles/Al matrix composites①
(1. Institute of Materials and Technology,
Dalian Maritime University, Dalian 116026, P.R.China;
2. State Key Laboratory of Structural Analysis of
Industry Equipment, Dalian 116024, P.R.China;
3. Department of Material Engineering,
Dalian University of Technology, Dalian 116026, P.R.China)
Dalian Maritime University, Dalian 116026, P.R.China;
2. State Key Laboratory of Structural Analysis of
Industry Equipment, Dalian 116024, P.R.China;
3. Department of Material Engineering,
Dalian University of Technology, Dalian 116026, P.R.China)
Abstract: Diffusion-controlled phase transformations and tribological properties and hardness of Al65Cu20Cr15quasicrystal particles(QCp)/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 phase with the microstructure of monoclinic of Al13Cr2through 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′-Al2Cu andθ-Al2Cu, are separated out from the Al matrix respectively after hot-pressing. The QCp/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 1200MPa, being 4 times that of Al. The frictional coefficient and the wear rate of the QCp/Al are lower than those of Al. In comparison with SiCp/Al matrix composites, QCp/Al composites have higher hardness and lower frictional coefficient.
Key words: composites; quasicrystals; aluminium alloys; phase transformation