间隙原子O对高Nb-TiAl合金显微组织与相转变的影响  

EFFECT OF OXYGEN ON MICROSTRUCTURE AND PHASE TRANSFORMATION OF HIGH Nb CONTAINING TiAl ALLOYS

作　　者：吴泽恩[1] 胡锐[1] 张铁邦[1] 周欢[1] 寇宏超[1] 李金山[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《金属学报》2013年第11期1381-1386,共6页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51001086;51371144;国家重点基础研究发展计划项目2011CB605503资助~~

摘　　要：采用真空非自耗电弧炉制备了不同含O量的Ti-46Al-8Nb-xO(原子分数)合金铸锭,研究间隙原子O对高Nb-TiAl合金凝固组织及相转变的影响规律和作用机制.结果表明,随着O含量的增加,Ti-46Al-8Nb-xO铸锭中α_2相含量逐渐增加.O的加入明显细化合金组织,并且使得组织由双态组织向全片层组织转变.间隙原子O的添加使得Ti-46Al-8Nb合金由β相领先的凝固方式转化为以α相领先的凝固方式,同时使包晶反应α+L→γ向低Al区移动,共析反应α→α_2+γ向高Al区移动,扩大了α相区的范围.通过DSC分析表明,O原子可以明显提高合金的共析反应温度,但随着含量的增加作用效果逐渐减弱.Due to the low density, high specific strength, elastic modulus and oxidation resistance at high temperature, TiAl-based alloys have attracted much attention as a candidate of the next generation high temperature materials in aerospace and automobile application. Meanwhile, the excellent properties oxidation resistance, creep strength and tensile strength at the elevated temperature make the high Nb containing TiAl alloys be one of the promising development directions of future TiAl alloys. During the studies about alloying which is an efficient way to improve the performance of TiAl alloys, researchers have found that interstitial atoms B, C and N notably refine the grains and then improve mechanical properties including yield strength, micro-hardness, and tensile ductility of TiAl alloys. During the melting, casting, forging and the application environment, the TiAl alloys also are always inevitable to be contaminated by the O. In this work, the high Nb containing Ti-46Al-8Nb-xO alloys （atomic fraction） were prepared by non-consumable vacuum arc remelting under the protection of Ar atmosphere. The aim of the present work is to study the influence and the corresponding mechanism of oxygen atoms on the microstructure evolution and phase transformation of high Nb-TiAl alloys. The results indicate that oxygen atoms in Ti-46Al-8Nb-xO alloys remarkably increase the amount of α2 phase. The increasing oxygen content leads to the grain refinement. Meanwhile, the duplex microstructures translate into fully lamellar. It indicates that the interstitial oxygen essentially reduces the kinetics of α→γ. Consequently, the fully lamellar is easier formation than the duplex microstructures. It is found that interstitial oxygen atoms preserve significantly influence on the microstructure of Ti-46Al-8Nb-xO alloys. With the increase of oxygen content, the β solidification translates into αsolidification and the peritectic reaction α＋L→γ moves to a lower Al content. At the same time, the eutectoid reactionα→α2＋

关 键 词：高Nb—TiAl合金 间隙原子O 凝固行为 相转变 

分 类 号：TG146.2[一般工业技术—材料科学与工程]