TiC增强相对Mo合金力学性能与显微组织的影响

【作者】 卢明园；

【导师】 范景莲；

【作者基本信息】 中南大学 ， 粉体材料科学与工程， 2009， 硕士

【摘要】 碳化物增强钼合金由于具有良好的室温强韧性、高温强度和高的再结晶抗力等优良的力学性能,可在高温、高应力等条件下稳定服役,是应用于新一代高速飞行器动力系统、火箭推进器及其供能系统的一种颇具发展潜力的耐热钼材。本论文在Mo-Ti合金的基础上,引入TiC增强相,探索TiC的添加对Mo-Ti合金力学性能及显微组织的影响,同时对碳化物相在钼基体中的强化作用进行讨论。由此,本实验采用粉末冶金方法制备TiC成分在0.05-0.25wt.%及2-12wt.%内的Mo-Ti-TiC合金,测试合金的室温及800℃下的拉伸性能,并对合金的显微组织形貌进行表征。研究结果如下：(1)微量TiC(0.05-0.25wt.%)的添加使得Mo-Ti合金的强度得到了提高。其中,TiC的添加量为0.05wt.%时,Mo-Ti-TiC合金的强度最高,强度较Mo-Ti合金提高31.7%。(2)微量TiC在Mo-Ti-(0.05～0.25wt.%)TiC合金中形成0.5～1.5μm的(Ti,Mo)xOyCz的第二相粒子,起到净化晶界氧及细化晶粒作用,合金的晶粒尺寸随着TiC添加量的增加而降低。(3)高TiC含量(2～12wt.%)的Mo-Ti-TiC合金具有更为良好的力学性能,当TiC含量为4wt.%时,1920℃烧结的Mo-Ti-TiC合金的室温及800℃拉伸强度均达到最高,分别为700MPa和476MPa。800℃下拉伸,Mo-Ti-2TiC和Mo-Ti-4TiC合金存在明显屈服现象,屈服强度分别为325MPa及410MPa, TiC含量较高的Mo-Ti-6TiC和Mo-Ti-8TiC合金无屈服现象,为典型的脆断。(4)随着TiC含量的提高,Mo-Ti-(2～12wt.%)TiC合金中的碳化物相数量增多,尺寸变大,从而使得合金的晶粒尺寸降低,硬度提高。更多还原

【Abstract】 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.更多还原