Research On The Preparation And Properties Of Al₃ti_p/mg Composite Materials

Magnesium matrix composites have become a research hotspot in the field of metal matrix composites for their advantages such as low density, high specific strength, high specific modulus, excellent damping capacity, and high wear resistance, etc. In this paper, Al3Ti particle reinforced magnesium matrix composites were prepared by two various powder metallurgy methods through in-situ synthesis method and mechanically mixing. The microstructure, the phase composition of the composite, mechanical properties, friction and wearing properties were discussed.The experimental results showed that the relatively pure Al3Ti powder could be prepared by heating the ball-milled mixed Al, Ti powder with the 3:1 atomic ratio at 750℃for 2h. After the mixed AlTi, Mg powders with a certain atomic ratio were ball-milled, pressed with 500MPa and heated at 750℃for 2h, Al3Tip/Mg composite materials were prepared by mechanically mixing, among which the Al3Ti phase were uniformly distributed and the particle size was 5-20um. After mixed the Mg, Al, Ti powders in accordance to a certain proportion ratio, ball-milled, pressed with 500MPa and heated at 700℃for 2h, Al3Tip/Mg composite materials, with uniform Al3Ti particle size distribution and particle size 1-5um, were prepared by in-situ synthesis method.The experimental results showed that the hardness and compressive strength could be improved by increasing the Al3Ti content, and the in situ synthesis method had lead to the higher performence than mechanically mixing method. The hardness of the composite is about 2-2.5 times that of pure magnesium and the compressive strength is about 1.5-2 times that of pure magnesium. When excess 5%Al, excess 5%Al+1% Zn,1% rare earth oxides were added espectinvely into the the mixed Al, Mg powders and the composite were prepared by in situ synthesis method, Al3Ti particle became smaller, and the material's shrinkage porosity and Al3Ti particle agglomeration were effectively reduced, so that the hardness and compressive strength of composite materials were improved. The best hardness was acquired when the excess 5%Al+1%Zn was added and the best compressive strength was acquired when 1% rare earth oxides was added.The composites perform the good wear resistance when prepared by both the two methods. Best wearability is acquired when the Al3Ti content is 20% for composite prepared by the in-situ synthesis method, but when the Al3Ti content is 30% for the mechanically mixing method. The main wear mechanism of the composites is abrasive wear.After the composite materials were processed by hot pressing at 400℃, a lot of the shrinkage porosity in powder metallurgy materials could be effectively eliminated. The density of the materials was increased, and the flexural strength was improved effectively, as which was about 1.5～2 times of pure Mg and would be improved with the of Al3Ti content increasing.