| In the process of aluminum melting, squeeze casting and die casting, the corrosion-wear of the molten aluminum is one of the main causes of the failure of the crucibles, barrel and mold. Studding the corrosion-wear mechanism of materials is of great significance to develop materials used for molten aluminum corrosion-wear condition. Ti Al3 intermetallic compound has excellent high temperature oxidation and wear resistance, and totally does not react with molten aluminum, so it is a potential material resistant to aluminum corrosion-wear.In this paper, Ti3 Al C2/Ti Al3 in-situ composite were successfully synthesized by mechanical milling and reactive hot pressing process of Ti/Al/C elemental powders. The influence of the sintering process and Ti3 Al C2 content on microstructure and properties of composite were systematically studied. The corrosion-wear behaviors of Ti3 Al C2/Ti Al3 composite in molten aluminum were investigated using a self-developed high temperature corrosion-wear teat apparatus in comparison to H13 tool steel. The corrosion-wear interaction mechanism were discussed. The main research results are as follows:(1) A large number of lattice distortion energy were stored in the mixed powders during50 h milling process, Ti Al3 can be generated through Ti-Al solid phase diffusion reaction before Al melt during heating process. When heated to temperature above the melting point of Al, violent exothermic reaction would occur between Ti-Al components, generating a large number of Ti Al3, some Ti Al3 would further react with Ti in Ti-rich area to produce Ti Al; at higher temperature, the remaining Ti would react with C and generate Ti C, the Ti C would further react with Ti Al, and generate Ti2 Al C and Ti3 Al C2, Ti2 Al C could continue react with Ti C at temperature above 1200℃ and generate Ti3 Al C2. The overall reaction included Ti Al,Ti C, Ti2 Al C as intermediate phases.(2) The optimum process parameters to fabricate composite is at 1250℃ for 30 min,and the optimum volume fraction of Ti3 Al C2 is 20vol%. The microstructure of the composite is three-dimensional network Ti3 Al C2 uniformly distributed in the matrix Ti Al3. The three point flexural strength, fracture toughness and compressive strength at room temperature was354MPa、14.3MPa/m1/2 and 1449.8MPa respectively. Compared to single-phase Ti Al3, the flexural strength and fracture toughness of the composite were increased by 118.5% and 6times. The strengthen mechanisms include grain refinement caused by network Ti3 Al C2 and residual compressive stress caused by thermal expansion coefficient difference between Ti3 Al C2 and Ti Al3. The fracture surface of composite showing a typical “quasi-plasticdeformation” feature, toughening mechanism included strip and spall of Ti3 Al C2 particles and crack deflection and bridging.(3) Compared to H13 tool steel, the corrosion-wear resistance of Ti3 Al C2/Ti Al3 composite has improved 7 times. The corrosion rate of composite in 750℃ aluminum is0.17×10-2mm/h, which is only 1/50 compared to H13 tool steel, because the composite does not form new interface product in liquid aluminum, only a small amount of Ti dissolved in the melt. In high temperature dry wear process, the wear mechanism of the composite is abrasive wear and adhesive wear caused by oxide layer. The wear rate of the composite is slightly higher than H13 tool steel because oxide film is not dense owing to the oxidation rate between Ti3 Al C2 and Ti Al3 is inconsistent. The corrosion of the Ti3 Al C2/Ti Al3 composite reduced the wear resistance of the material in one hand and corrosion products exacerbated abrasive wear on the other hand. While the composite wear in liquid aluminum, the rotating of the friction pair accelerated aluminum dilution near the composite and improved corrosion rate. The interaction between the corrosion and the wear at the same time, resulting in corrosion-wear failure. |
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