Research On The Preparation Technology And Properties Of TiC Particulate Reinforced AZ91Magnesium Matrix Composites

Thermodynamic calculations were carried on in the Al-Ti-CaC₂system to analyze thefeasibility of in situ reaction synthesis TiC particles and the result was verified by experiment.The TiC_p/Al master alloy was prepared by the Al-Ti-C-CaC₂enhanced system and in situsynthesis reaction. TiC_p/AZ91magnesium matrix composites with different TiC content wereprepared by remelting dilution solution and by stir casting process. In order to improve thestrength, elongation and other significant properties, the TiC_p/AZ91magnesium composites wasalso rolled. The microstructure, mechanical properties, friction and wear characteristics ofTiC_p/AZ91magnesium matrix composites which was cast and rolled were test by using opticalmicroscope, SEM, XRD, EDS and other equipments.Thermodynamic calculation shows that the formation of TiC in the Al-Ti-CaC₂system hada lower ΔG and higher Tad, which came to the thermodynamics condition for preparation of TiC.The presence of the TiC was verified by the means of XRD and EDS test. Ca contained TiC_p/Almaster alloy was successfully prepared by the combining Al-Ti-CaC₂system with Al-Ti-Csystem.Different TiC content of4%,8%,12wt.%TiC_p/AZ91magnesium matrix composites wasprepared by semi-solid mixing. With increasing the amounts of TiC, the cast TiC_p/AZ91composite material grain could be refined. β-Mg17Al12can be attached to the precipitation of TiCparticles, and TiC was conducted as the heterogeneous nucleation. However, the more TiCcontents the more agglomeration and defects appeared in the microstructure such as obviouspores, shrinkage and so on. With the increase of TiC content, the hardness of the magnesiummatrix composites significantly improved, however, tensile strength and elongation declinedafter first going up with increasing the TiC content,8wt.%TiC of TiC_p/AZ91magnesium matrixcomposites had the best properties among these. The increasing TiC contents improved the wearresistance of TiC_p/AZ91magnesium matrix composites significantlyHot pressing and rolling of TiC_p/AZ91magnesium matrix composite was carried on under aheating temperature of653K and total deformation of70%. With the increasing of TiC content,the available rolling properties of the magnesium matrix composites decreased. Micro-cracksappeared on the surface of8wt.%TiC_p/AZ91magnesium matrix composites while the obviouscracking on the surface of TiC_p/AZ91magnesium matrix composites who contained12wt.%TiC.The grain of TiC_p/AZ91magnesium matrix composites was refined, whose tensile strength andelongation was significantly improved than the cast one. When the contents of TiC increasedfrom4wt.%to8wt.%, the tensile strength of the magnesium matrix composites did not variedvery much, meanwhile the elongation of the magnesium matrix composites decreased monotonically.