富氮网状核壳结构Ti-6Al-4V合金组织和力学性能研究

Microstructure and Mechanical Properties of a High-Nitrogen Core-Shell Network Structured Ti-6Al-4V Alloy

采用放电等离子烧结(SPS)技术将经过高温渗氮处理的Ti-6Al-4V (TC4)粉末制备成致密的核壳(core-shell,CS)结构TC4。并对核壳结构TC4合金在1000℃下进行固溶处理,研究了采用不同冷却速度的冷却方式以及不同温度时效处理对核壳结构TC4合金微观组织和力学性能的影响。利用光学显微镜(OM)和扫描电子显微镜(SEM)对核壳结构TC4合金的显微组织和截面形貌进行分析。发现壳层具有接近单一的α相,而核心为α+β相,并且β相连续分布在α相之间,最终形成了这种新颖的核壳结构。在氮的固溶强化和核壳结构的双重作用下,核壳结构TC4合金屈服强度达1180 MPa,断裂延伸率约为10%,力学性能显著提高。通过固溶和时效处理调节壳和核的微观结构,可以进一步提升材料的性能。

Completely densified core-shell （CS） structured Ti-6Al-4V （TC4） compact was fabricated by powders nitriding and subsequent spark plasma sintering （SPS） technique. The nficrostructures and mechanical properties of CS-TC4 after solution treatment and ageing were investigated. The cross-section microstructures of nitrided TC4 powder and sintered core-shell structured TC4 compact were characterized by optical microscope （OM） and scanning electron microscope （SEM）. The mechanical properties of the compacts were also measured. Results showed that the shell consists of near single a phase while core is mainly composed of α laths and β lamellae. Phase transformation from （α＋β） phase to a near single a phase in shell is attributed to the nitrogen diffusion, which results in such a novel CS structure. The CS-TC4 compact exhibits yield strength of about 1180 MPa and a fracture elongation of 10%. Such mechanical properties should be attributed to the effects of solid strengthening of nitrogen and the unique core-shell structure. The mechanical properties can be further enhanced through solution and aging treatment for a reasonable microstructure controlling.