Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problem...Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problems,but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys.Here,an intera-tomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed.The ternary potential can accurately predict the structure and thermodynamic properties of the Nb-Al-Ti system.The potential shows that the optimal Nb content for high-temperature strength-ductility synergy of TiAl single crystals is 8%,consistent with the amount of miracle synthesis of TiAl single crystals.Tensile simulations further show that the developed potential can make an effective prediction at high temperatures,indicating the potential for the development and applications of high-temperature Nb-Al-Ti ternary systems.展开更多
激光定向能量沉积(laser-directed energy deposition,LDED)成形Ti-Al合金的微观组织通常表现为贯穿多个熔池的粗大柱状晶,使得该合金较难获得均匀的力学性能。本文选用Nb作为Ti-Al二元合金的添加元素,通过LDED技术成形一系列Ti-6Al-x N...激光定向能量沉积(laser-directed energy deposition,LDED)成形Ti-Al合金的微观组织通常表现为贯穿多个熔池的粗大柱状晶,使得该合金较难获得均匀的力学性能。本文选用Nb作为Ti-Al二元合金的添加元素,通过LDED技术成形一系列Ti-6Al-x Nb(x=5、6.5、7.5,质量分数)三元合金,采用光学显微镜、X射线衍射仪、扫描电镜和电子背散射衍射仪对合金的微观形貌、室温拉伸性能以及变形机制进行研究,探究Nb含量对LDED成形Ti合金微观组织及拉伸性能的影响。结果表明:不同Nb含量合金的微观组织形貌较为接近,均主要由细长的针状或片层状α/α′相组成,且存在少量的残余β相。当Nb质量分数为6.5%时,合金具有最高的极限抗拉强度((902±35)MPa)和屈服强度((849±20)MPa),这主要归因于晶粒尺寸的减小。此外,随Nb含量增加,合金的伸长率逐渐降低。当Nb质量分数为7.5%时,合金的伸长率最低,为(10.2±1.4)%。展开更多
基金the National Key Research and Development Program of China(Grant No.2019YF40705400)National Natural Science Foundation of China(Grant Nos.51535005,51731006,and 51771093)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Me-chanical Structures(Grant Nos.MCMS-I-0418K01,MCMS-I-0419K01)the Fundamental Research Funds for the Central Universities(Grant Nos.NZ2020001,NC2018001,NP2019301,NJ20I 9002,and 30919011295)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problems,but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys.Here,an intera-tomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed.The ternary potential can accurately predict the structure and thermodynamic properties of the Nb-Al-Ti system.The potential shows that the optimal Nb content for high-temperature strength-ductility synergy of TiAl single crystals is 8%,consistent with the amount of miracle synthesis of TiAl single crystals.Tensile simulations further show that the developed potential can make an effective prediction at high temperatures,indicating the potential for the development and applications of high-temperature Nb-Al-Ti ternary systems.
文摘激光定向能量沉积(laser-directed energy deposition,LDED)成形Ti-Al合金的微观组织通常表现为贯穿多个熔池的粗大柱状晶,使得该合金较难获得均匀的力学性能。本文选用Nb作为Ti-Al二元合金的添加元素,通过LDED技术成形一系列Ti-6Al-x Nb(x=5、6.5、7.5,质量分数)三元合金,采用光学显微镜、X射线衍射仪、扫描电镜和电子背散射衍射仪对合金的微观形貌、室温拉伸性能以及变形机制进行研究,探究Nb含量对LDED成形Ti合金微观组织及拉伸性能的影响。结果表明:不同Nb含量合金的微观组织形貌较为接近,均主要由细长的针状或片层状α/α′相组成,且存在少量的残余β相。当Nb质量分数为6.5%时,合金具有最高的极限抗拉强度((902±35)MPa)和屈服强度((849±20)MPa),这主要归因于晶粒尺寸的减小。此外,随Nb含量增加,合金的伸长率逐渐降低。当Nb质量分数为7.5%时,合金的伸长率最低,为(10.2±1.4)%。
