Papers by Author: Gui Song Wang

Abstract: The dry sliding characteristics of three in situ Al₂O₃/Al-Si composites fabricated with volume fraction of 10, 20 and 30 vol.% were investigated. The effect of sliding parameters on the wear properties was investigated. As the sliding velocity increases the wear loss decreases systematically. When the volume fraction increased to 20 vol.%, an improvement of wear resistance was obtained. However, when the volume fraction was 30 vol.%, a further decrease of wear resistance was observed. In case of low volume fraction (10 vol.%), an extensive plastic deformation by plowing out the ductile Al matrix along with narrow grooves was observed. As the volume fraction increased to 20 vol.%, the abrasive wear by micro grooving is dominant as well as the low load is used. Whereas, when the volume fraction increased to 30 vol.%, besides the effect of large pores, the embedded Al₂O₃ in the massive Si blocks formed a weaker interface thereby behaving as source of crakes initiation and propagation. As result, fracture, micro-cutting and delaminating are observed as dominant abrasive wear mechanisms

Abstract: In this paper, the milling process of WO3 and aluminum particles is studied. Influences of rotate rate, milling time and ball-to-powder weight ratio on the morphology and grain size of the particles are studied by scanning electronic microscope and X-ray diffraction techniques. Al particle size decreases firstly and then increases with increasing milling time, while Al grain size decreases gradually as the milling time increases. WO3 particle is distributed uniformly in Al particles after milling for 9h, and has no marked change as further extension of milling time. With increasing the ball-to-powder weight ratio and rotate rate, both particle size and grain size of Al decreases. milling parameters have almost no effect on the grain size of the WO3 particles.

Abstract: (α+β)/β phase transformation temperature of a TC11 titanium alloy was confirmed to be 1035°C, which was obtained by three methods including the calculation method, differential scanning calorimetry and metallographic techniques. Based on this result, annealing treatments below and above the (α+β)/β phase transformation temperature were carried out, and the microstructure of the TC11 alloys before and after annealing treatment was analyzed by SEM. The result showed that conventional annealing below 1035°C does not change the Widmanstaten structure of TC11 alloy, though the thickness of α lamellar structure becomes thicker with increasing the annealing temperature. The microstructure of the TC11 alloy treated by annealing above the α+β/β transformation temperature is non-uniform because of the different forming temperature and growing duration of α phase in the TC11 alloy.

Abstract: The two (Al2O3+TiB2+Al3Ti)/Al composites were fabricated from Al-B2O3-TiO2 and Al-B-TiO2 raw powders by reactive hot pressing, respectively. The microstructure of in situ two composites was analyzed by OM, SEM and TEM. The results showed that coarse Al3Ti blocks with several tens of micrometers size were formed during hot pressing. The equiaxed Al2O3 particulates and hexagonal TiB2 particulates with finer sizes were formed in the composites simultaneously. The microstructure formation mechanism of (Al2O3+TiB2+Al3Ti)/Al composites were discussed. The results showed that Al2O3 reinforcements were formed on the surface of TiO2 or B2O3 powder and TiB2 particles were formed on B or B2O3 powders. The formation of coarse Al3Ti block is result from continuous diffusion of Ti in liquid Al during reactive hot pressing. In addition, there are fine Al3Ti precipitates exist in the composite fabricated from Al-B-TiO2 powders. This contributes to the improved mechanical properties in terms of yield and ultimate stresses and Young’s modulus of the composite.