The Dry Friction And Wear Behavior Of In-situ TiB₂/ZL203Composites

Particle reinforced aluminum composites have taken great attentions for theirexcellent physical and mechanical properties. Especially the particle reinforcedaluminum composite prepared by in-situ synthesis is considered to be a substitute oftraditional casting wearable materials, since it has high resistance to temperature, highresistance to abrasion and fatigue resistance, and it has become a new hotspot ofcurrent researches. Explore the preparation technology of particle reinforcedaluminum composite and study on its friction and wear properties has theoreticalsignificance and practical value for the preparation of particle reinforced aluminumcomposites.In this paper, TiB₂/ZL203composites were fabricated by a new method called“mixed-salt reaction in-situ synthesis process”, and the effect of TiB₂contents on theas-cast microstructure, mechanical properties and tribology behavior of thecomposites were investigated. This TiB₂/ZL203composites had well solved theproblems of traditional particle reinforced aluminum composites have low mechanicalproperty index and low wear-resisting performance, because of the unevenmicrostructures, coarse grains, interface pollutions, and other defects in vary degree.Crystalling phase structure analysis and mechanical properties test results showthat: the distribution of TiB₂particles which was prepared of in-situ was uniformlyand had small size. As the content of TiB₂increasing, the matrix grain sizesignificantly reduced, and the matrix microstructure of the composites had beenrefined. Though the hardness, tensile strength and yield strength of compositesincreased gradually, the elongation declined as the content of TiB₂increasing. Whenthe content of TiB₂particle reached up to10%, the tensile strength, yield strength andhardness of composites was335MPa,433MPa and238HV and compared with matrixalloy they were respectively increased60%,66%and118%. But the elongation was2.1%, declined75%compared with matrix alloy. The fracture mechanism of thecomposites was ductile fracture, and the strengthening mechanisms were fine-grainstrengthening, dispersion strengthening and dislocation proliferation strengthening.Dry sliding friction and wear test results show that：the wear resistance of thecomposites had increased dramatically as the content of TiB₂increasing; with thenormal load, sliding time and sliding speed increasing, the wear loss of the composites increased, and the increasing trend particularly in the low content of TiB₂;the wear loss of the composites was less than matrix alloy in general. The analysisresults of wear surface, subsurface and wear debris showed that the frictionphenomenon of matrix alloy and composites were the comprehensive effect of severalfriction mechanisms, with the friction conditions changing, the wear mechanisms ofthe material changed also. The wear mechanism of matrix alloy was mainly adhesivewear along with oxidative wear and delamination wear. The wear mechanism ofcomposites was mainly abrasive wear along with oxidative wear and delaminationwear. Because of the addition of the particle-reinforced TiB₂, the wear resistance ofthe composites was superior to the alloy. The particle-reinforced TiB₂has doublefunction to the composites during the course of friction. Before fracturing, TiB₂protected matrix material from sticking friction. When TiB₂broke, it changed toabrasive grain and resulted in drastic abrasive wear.