No abstract

The sliding wear behaviours of an unreinforced monolithic Al -Si -Cu alloy and SiC particles reinforced composites containing 5, 13, 38 and 50 vol.-% with diameters of 5 . 5, 11 . 5 and 57 mm were investigated. The results showed that the wear resistance of the composites is much higher than the monolithic alloy, and the larger and the more SiC particles, the higher the enhancement of the wear resistance. Metallographic examinations revealed that the subsurface of worn composites was composed of both fragmented particles and deformed matrix alloy. The depth of the particle fracture zone in the subsurface varied in the range of 20 -35 mm at a sliding distance of 1 . 8 km, while the plastic deformation zone of the worn subsurface on monolithic alloy was more than 100 mm. Scanning electron microanalyses of the worn surface, subsurface microstructure and debris suggested that the depth of the particle fracture zone became smaller as the diameter of SiC particles increased. Increasing the hardness and decreasing the applied wear stress changed the debris morphology from ake to very small lumps. MST/5643The authors are in the

In this study, 7075 aluminum matrix composites reinforced with 1.5 wt.% nanosized Al2O3 were fabricated by ultrasonic vibration. The effect of T6 heat treatment on both microstructure and hardness of nanosized Al2O3 reinforced 7075 (Al2O3np/7075) composites were studied via scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy, and hardness tests. The Mg(Zn,Cu,Al)2 phases gradually dissolved into the matrix under solution treatment at 480 °C for 5 h. However, the morphology and size of Al7Cu2Fe phases remained unchanged due to their high melting points. Furthermore, the slenderness strips MgZn2 phases precipitated under aging treatment at 120 °C for 24 h. Compared to as-cast composites, the hardness of the sample under T6 heat treatment was increased ~52%. The strengthening mechanisms underlying the achieved hardness of composites are revealed.

Wear behaviour was investigated for high volume fraction SiC particulate reinforced aluminum alloy composites by considering the shear stress acting on the specimen and the wear debris formed during sliding wear. The SEM morphology of worn subsurfaces showed that particles are fragmented, mechanically mixed, and then aligned in the wear direction caused by normal and tangential stresses. Wear debris were initially tiny lumps but nally delaminated due to the shear stress. A theoretical wear model was proposed for plastically deformable specimens worn by a rigid non-deformable steel ring by analysing the interspacing of SiC particles and the tangential stress applied to the worn surface. Predictions of this theoretical wear model were in good agreement with experimental results. MST/5686The authors are in the

A novel amorphous Al70Fe25Zr5 alloy was synthesised through high energy ball milling the mixtures of Al, Fe and Zr powder with the milling intensity of 150G (G is the gravitational acceleration). By comparing with the binary Al–Fe amorphous, differential scanning calorimeter results indicated the crystalline temperature of ternary Al70Fe25Zr5 amorphous alloy shifts higher temperature, and it showed two stages of crystalline reactions which corresponded to the formation of Al5Fe2 and Al3Zr phases respectively. Improvement of the thermal stability for this novel Al70Fe25Zr5 amorphous alloy is explained in terms of the total structure factor that was determined by the X-ray diffraction method.