碳对高温钛合金Ti-60组织和性能的影响

Effect of carbon on microstructures and mechanical properties of Ti-60 high-temperature titanium alloy

在Ti-60合金中碳的加入量大于0.17%时,组织中析出TiC结构的碳化物.在α+β相区再结晶,碳偏聚于初生α(α_p)相,导致碳化物主要在β转变组织中析出,其析出的百分数取决于α_p体积分数.在β相区热处理,析出的碳化物钉扎β原始品界,阻碍β晶粒的长大.β晶粒尺寸D、碳化物颗粒直径d和体积分数f三者遵循D/dαf^(-1/3)关系.随着碳含量的增加,β晶粒尺寸减小,α′片层通过界面迁移迅速长大以及形成α片层的合金元素的扩散速度加快,导致α′或α片层的厚度增加.碳的加入量小于0.09%时,碳完全固溶于基体中,产生固溶强化,β晶粒细小,导致合金的强度和蠕变抗力提高.碳含量增加导致粗大碳化物颗粒的析出,变形时产生应力集中使合金的塑性和蠕变性能降低.

Carbon additions greater than 0.17% produce carbide precipitation in the microstructure of Ti-5.6Al-4.SSn-2Zr-IMo-0.35Si-0.7Nd titanium alloy. During recrystallization in the α＋β phase field, carbon localizes in the primary α（αp） phase, resulting in that carbide particles preferentially form from the grains of bimodal microstructure and its volume fraction is determined by that of the αp. Precipitates of carbide during β annealing are distributed on the prior β grain boundaries or within the grain, and an obviousβ grain refinement was observed due to the grain-boundary pinning effect of carbide. The ratio of pinned β grain size （D） to carbide particle size （d） was found to be proportional to f-1/3, the volume fraction of carbide. The α＇ or α plate sizes increased because of the carbon addition. Carbon solubility in the phases concerned is closely related to the variation of mechanical properties.