| Particle-reinforcement aluminum matrix composites fabricated by in-situ reaction method have been a research foucs of the aluminum matrix composites, because of their low density, high specific strength and wear-resistance property, etc. But the reinforced particles are fine and the interfacial energy of system is high. In order to reduce the interfacial energy of system, the particles tend to segregation in matrix, which would have negative influence on the organization and properties of composites. However, rare earth is active substance, which reduces effectively the viscosity and interfacial energy of system and improves the wettability. The segregation tendency of particles reduces. So adding a balanced amount of rare earth has great effect on the micro structure and properties of composites.In this article, rare earths were added when fabricating TiC-Al2O3co-reinforced aluminum matrix composites through in-situ Contact Reaction method and Exothermic Dispersion method (XDTM). The effect of rare earths on the phase composition, morphology of microstructure and properties of composites were analyzed by SEM, XRD, EDS, hardness test and electrochemical testing.The experimental results show that the grains of TiC-Al2O3p/ZL205composites refine and their hardness and self-corrosion current density (Icorr) increase, their corrosion resistance reduces with the increasing of particles contents. When the contents of particles reach tol5wt%, the hardness of composite can reach96.32HV, compared with the matrix increase by65%. The self-corrosion current density (Icorr) of composite can reach4.501×10-4A·cm-2(the matrix:1.890×10-5A·cm-2). Compared with the matrix, the Icorr obvious increased. Thus, the adding extra particles can improve the hardness. Conversely, reduce the corrosion resistance of composites.Heat treatment is shown to have no effect on the distribution, shape and size of reinforced particles. But a mass of dispersion0" phase and T phase were precipitated in the matrix, which lead to increase the hardness and to reduce the Icorr, and to improve the corrosion resistance of the composites. The hardness of10wt%TiC-Al2O3p/ZL205composite without added rare earth improves from78.84HV to155.23HV. The Icorr of composite reduces from2.128×10-4A·cm-2to5.589×10-5A·cm-2. Thus, the hardness and corrosion resistance of composites are improved simultaneously.The microstructure and properties of10wt%TiC-Al2O3p/ZL205composites trend to better firstly and then worse with increasing of the Ce or La contents. When the contents of Ce or La are0.3wt%or0.2wt%respectively, the contents of TiC and Al2O3particles increase and the distribution of particles becomes uniform. The rodlike Al3Ti phases of the composites are decreased or passivated. The microstructure and hardness of the composites are the best. The hardness at casting condition of the composites is95.73HV and85.74HV respectively. The hardness at heat treatment condition is211.03HV and202.23HV respectively. The Icorr of composites achieves the minimum. The corrosion resistance is best. The Icorr at casting condition of composites is3.036×10-5A·cm-2and4.053×10-5A·cm-2respectively. The Icorr at heat treatment condition is8.735×10-6A·cm-2and9.169×10-6A·cm-2respectively. Thus, the micorostructure, hardness and corrosion resistance of composites are simultaneously improved.10wt%TiC-Al2O3p/Al composites were fabricated by the Exothermic Dispersion method (XDTM), the XDTM reinforcements are in-situ TiC phases and Al2O3phases, and the two phases combine together in the process of reaction. CeO2or La2O3in high temperature could decompose into releasing [Ce] or [La]. So there is the same influence with pure Ce or La. When the contents of CeO2or La2O3are0.3wt%or0.2wt%respectively, the rodlike Al3Ti phases disappear. The contents of TiC and Al2O3particles increase and their distribution is more uniform. So the hardness of the composites is the highest with60.21HV and56.26HV respectively. Compared with the matrix (21.34HV), their hardness significantly increases. |
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