Fabrication And Study On Properties Of Al₃Ti Particles Reinforced Magnesium Matrix Composites

Al₃Ti/Mg composite has been in situ synthesized by the powder metallurgy of Mg-Al-Ti system.The phases and microstructures of the composite were studied using thermodynamics analysis,X-ray diffractometry(XRD),scanning electron microscopy(SEM)and energy dispersive spectrum(EDS).The properties of the composites were also evaluated.Based on these studies,the affects of ingredient, sintering temperature and holding time on microstructures and properties were analyzed.The heats of formation of Mg-Al,Mg-Ti and Al-Ti system were counted out through Miedema's model and Gibbs' free-energy.Al₃Ti intermetallics could be forecasted to form by Al-Ti reaction in Mg-Al-Ti system.It was found that based on the mol ratio of Al and Ti equalling 3,the additional amount of Al and sintering temperature below 1400K should require to eliminate residual Ti by whole reaction of Al₃Ti.The experimental results show that the in-situ Al₃Ti reinforced Mg matrix composites are composed of Al₃Ti and Mg,with dense microstructures.The composites are characterized by a relatively homogeneous distribution of Al₃Ti particulates with a size range of 2-4μm and a good cohesion at the matrix/particulate interfaces.Compared with AZ31 magnesium alloy,the coefficient of thermal expansion(CTE)values of Al₃Ti/Mg composite are lower;hardness,strength and wear resistance property are improved.The CTE values of Al₃Ti/Mg composite are reduced with the increase of the volume fraction of Al₃Ti.The compressive ultimate stress of 30vol.%Al₃Ti/Mg composite are 2 and 1.5 times higher than those of pure magnesium and AZ31 magnesium alloy respectively.The compressive ultimate stress of Al₃Ti/Mg is enhanced with the volume fraction of Al₃Ti.The wear loss of 25vo1.% Al₃Ti/Mg composite are 6 and 3 times lower than those of pure magnesium and AZ31 magnesium alloy,respectively.