注射成型低碳生物医用β钛合金碳化物析出机理与调控研究

The titanium (Ti) carbides in carbide-strengthened Ti-based materials usually exhibit large size, which is difficult to control. Based on a new discovery, i.e., the carbon solubility decreases significantly in Ti matrix after adding β-stabilizers, the present proposal focuses on the mechanism and control of carbide precipitation in Ti alloys with low carbon content, aiming at the development of precipitation-strengthened Ti alloys for biomedical applications. In this project, Ti-Mo alloys with carbon content lower than 0.08 wt.% will be fabricated by metal injection moulding (MIM). This research includes: 1) the investigation of the relationship between β-stabilizers in Ti matrix, lattice parameters of the matrix, the formation energy of the titanium carbide and temperature, by using first principle theory; 2) the study of the orientation relationship between the titanium carbide and the matrix, and the kinetics model of carbide growth, by using in situ microstructure and phase characterization; 3) the development of a MIM process to fabricate precipitation-strengthened β-Ti alloys with low carbon content, by investigating the influence of iron addition on the activated sintering of Ti-Mo alloys and the titanium carbide precipitation, as well as the effects of heat treatment processes on the morphology and content of titanium carbides. This project has important scientific significance for the study of the precipitation-strengthening phase in Ti alloys, and for the development of new powder metallurgy processed Ti alloys as biomaterials.

碳化物强化钛基材料中通常存在碳化钛颗粒尺寸较大，不易控制的问题。本项目利用添加β相稳定元素后，钛合金中碳固溶度显著下降的新现象，研究低碳含量下钛合金中碳化物沉淀析出新机理与调控方法，旨在开发沉淀强化生物医用钛合金。项目以注射成型(MIM)低碳(含碳量低于0.08 wt.%)钛钼(Ti-Mo)合金作为研究对象，拟通过第一原理计算β相稳定元素的种类与含量、基体晶格常数、碳化钛的形成能和温度的内在关系，揭示β相稳定元素对碳在钛合金中溶解度影响的内在机理；通过对显微组织与相组成进行原位测试，建立碳化钛析出位向关系与长大动力学模型；通过研究添加铁对Ti-Mo合金活化烧结和碳化钛析出的影响，以及热处理制度对碳化钛形貌与含量的影响，建立碳化钛沉淀强化低碳β钛合金MIM制备技术原型。项目成果将对钛合金中强化相的沉淀析出提供新的理论依据，而且对新一代粉末冶金生物医用钛合金的开发具有重要的工程意义。

碳化物强化钛基材料中通常存在碳化钛颗粒尺寸较大，不易控制的问题。本项目利用添加β相稳定元素后，钛合金中碳固溶度显著下降的新现象，研究低碳含量下钛合金中碳化物沉淀析出新机理与调控方法，旨在开发沉淀强化生物医用钛合金。项目主要以注射成型（MIM）低碳(含碳量低于0.08wt.%)钛铌（Ti-Nb）基合金作为研究对象，通过计算与试验方法揭示了β相稳定元素的种类与含量对基体晶格常数和碳固溶度的影响机理；利用原位方法研究了碳化钛的溶解动力学及其析出过程中和基体之间的位向关系；通过研究添加Fe对Ti-Nb基合金的活化烧结机制，优化了烧结制度；通过研究添加Hf、Zr和B等元素以及热处理制度对碳化物析出相的含量与分布的影响。经过优化，沉淀强化低碳MIM Ti-Nb基合金中碳化物含量显著降低，分布更加均匀，力学性能也得到了明显改善。初步的体外试验显示，沉淀强化低碳MIM Ti-Nb基合金具有比传统商用纯钛更好的细胞相容性。由此基本形成了沉淀强化低碳β钛合金的MIM制备技术原型。项目的开展对了解钛合金中强化相的沉淀析出以及新一代粉末冶金生物医用钛合金的开发具有重要的科学及工程意义。