Microstructure and microhardness of Ti₃Al matrix composites produced by XD^TM synthesis

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ÎÄÕÂÒ³Â룺1138 - 1141

Key words£ºTi₃Al; Ti₃AlC; TiC; microhardness; elastic modulus

Abstract: XD^TMªªmethod was used to prepare titanium aluminide(Ti₃Al) matrix composites. The phase constitution and the as-cast microstructure of Ti-25Al alloy with different carbon contents have been investigated using XRD and SEM. Microhardness and elastic modulus of the matrix and reinforcements were tested by mechanical property microprobe. In Ti-25Al-0.5C alloy, blocky Ti₃AlC and lath Ti₃AlC were in-situ formed as reinforcement, and homogeneously distributed in the matrix. The microhardness and elastic modulus of blocky Ti₃AlC are 14.2GPa and 281.3GPa respectively, higher than those of the lath Ti₃AlC about 3GPa and 60GPa respectively. When C content is more than 0.5%, dendritic TiC and Ti₃AlC were formed as reinforcement in a core structure, where the TiC core is coated with Ti₃AlC phase. The microhardness and elastic modulus of the reinforcement decrease with increasing distance from the center of the reinforcement and matrix. The maximum microhardness and modulus of TiC and Ti₃AlC are 22.8GPa, 302.7GPa and 20.2GPa, 313.5GPa, respectively.