Tic Reinforced Relative Mo Alloy Mechanical Properties And Microstructure

Carbide reinforced molybdenum alloys are novel heat-resistance Mo-based materials developed for high temperature applications. Attributed to their high strength and toughness as well as resistance to recrystallization in high temperature, carbide reinforced molybdenum alloys are considered as promising candidate for high temperature structural materials used in future aerospace, nuclear power and military industries.This research aims to investigate the effects of TiC content on the mechanical properties and microstructure of TiC reinforced Mo-Ti-TiC molybdenum alloy and discuss the strengthening mechanism of the carbide phase in molybdenum matrix.Mo-Ti-TiC alloys were fabricated via Powder Metallurgy methods. The content of TiC was in the rage of 0.05-0.25wt.%and 2～12wt.%. Tensile properties of the alloys were tested and the microstructures of the alloys were characterized in terms of fracture morphology, grain size, as well as distribution and chemical composition of the carbide phase.(1) It is indicated in the result that tensile strength of Mo-Ti alloy is effectively enhanced by adding trace TiC (0.05-0.25wt.%). Mo-Ti-TiC with 0.05wt.%TiC in addition exhibits the highest tensile strength, which is 31.7.% higher than Mo-Ti alloy.(2) TiC particles form (Ti,Mo)xOyCz second phase particles during high temperature sintering. The number of second phase particles in the alloy increase with the rise of TiC content, which leads to the decrease of grain sizes since the second phase particles can inhibit the grain growth. Additionally, due to the affinity of TiC to oxygen at high temperature, TiC particles can suppress the oxygen segregation to the grain boundary.(3) Sintered at the temperature of 1920℃, Mo-Ti-TiC alloys with 2-12wt%TiC in addition show excellent mechanical properties both at room temperature (RT) and at 800℃. The highest tensile strengths of Mo-Ti-(2-12wt.%) TiC are obtained when 4wt.%TiC are added, which are 700MPa (RT) and 476MPa (800℃). The tensile load-displacement curves of Mo-Ti-2TiC and Mo-Ti-4TiC alloys at 800℃show obvious yield point elongation, with the yield strengths of 325MPa and 410MPa respectively. No sign of yielding is observed in Mo-Ti-6wt.%TiC and Mo-Ti-8wt.%TiC alloys which fracture immediately after elastic deformation.(4) With the increase of TiC content, the size and quantity of the carbide phases in Mo-Ti-(2-12wt.%)TiC alloy increase, thus leads to the decrease of the grain size and the increase of the hardness of the alloys.