摘要
为了制定新型β凝固γ-TiAl合金合理的热加工和热处理工艺,研究其相变行为和组织变化规律具有极其重要的指导意义。本工作设计出一种新型的Ti-Al-Mn-Nb合金,该合金的名义成分(原子分数,%)为Ti-43Al-1.5Mn-3Nb-0.2Si-0.2C-0.1B,采用Pandat热力学软件计算、EPMA、TEM、EBSD和XRD等方法,系统研究了该新型合金在1440℃至1000℃温度范围内的组织演变行为。结果表明,铸态合金组织由片层组织(α2/γ)和片层组织周围少量β_o/γ混合相组成。合金的凝固和固态相变路径为:liquid→liquid+β→β→β+α→α→α+γ→(α2+γ)→(α2+γ)+β_o→(α2+γ)+β_o+γg,其β转变温度(Tβ)约为1420℃,γ相溶解温度(Tγ,solv)约为1280℃,共析转变温度(Teut)约为1160℃。当温度略低于Tγ,solv时,由α相析出的γ呈片层状,α相和γ相始终存在Blackburn位向关系:(111)γ//(0001)α2、<1■0)>γ//<11■0>α2;由α相析出的β_o呈块状,遵循Burgers位向关系:(110)βO//(0001)α2、<111>βO//<11■0>α2。新型合金淬火组织的Vickers硬度位于385~512 HV范围内,随着淬火温度的升高淬火组织显微硬度提高,在β单相区淬火后生成的马氏体组织使得硬度达到512 HV。该新型合金同时具有β和α单相区,对发展可调控出全片层结构的易变形、高承温新型β凝固γ-TiAl合金具有重要指导意义。
γ-TiAl based alloys are advanced structural materials use in the automotive and aero-space industries.Their notable characteristics,including low density,high specific yield strength,and ex-ceptional resistance to creep and oxidation,make them highly viable for being used as structural compo-nents in high-temperature applications of internal combustion engines.The novelβ-solidifyingγ-TiAl alloy designed in this study demonstrated excellent oxidation resistance at temperatures of 750,800,and 850℃.However,research regarding the solid-state phase transformations and microstructure control of this alloy is lacking.The study of the phase transformation behavior and microstructural evolution of alloys is crucial for developing appropriate thermal processing and heat treatment techniques forβ-solidifyingγ-TiAl alloys.This work introduces a novel Ti-Al-Mn-Nb alloy,with a nominal composition of Ti-43Al-1.5Mn-3Nb-0.2Si-0.2C-0.1B(atomic fraction,%).Using Pandat software for thermodynamic calculations,along with techniques such as EPMA,TEM,EBSD,and XRD,an extensive and meticulous investigation of the microstructural transformations within the range from 1440℃to 1000℃for this innovative alloy was undertaken.The results indicate that the as-cast microstructure of the alloy comprises a lamellar colony(a_(2)/γ),grainγphase,and a small amount of_(o).The solidification pathway of the alloy can be determined as follows:liquid→liquid+β→β→β+α→α→α+γ→(α_(2)+γ)→(α_(2)+γ)+β_(0)→(α_(2)+γ)+β_(o)+γ_(g).The temperature at which the alloy exists as a singleβphase(T_(β))is approximately 1420℃,while the decomposition temperature ofγphase(T_(γ.solv))is approximately 1280℃;additionally,the eutectoid transformation temperature(T_(eut))is approximately 1160℃.Slightly below T_(γ.solv),theγprecipitated from theαphase exhibits a lamellar structure.Theαand y phases consistently demonstrate a Blackburn orientation relationship:(111)_(γ)/(0001)_(α)_(2),<110>_(γ)/<1120>_(α)_(2),respectively.The secondaryβ_(o)phase precipitated from theαphase appears as a block shape and follows the Burgers orientation relationship:(110)_(β)_(o)/(0001)_(α)_(2)<111>_(β)_(o)//<1120>_(α)_(2),The Vickers hardness of the quenched microstructure of the novel alloy ranges between 385 and 512 HV.With an increase in the quenching temperature,there is an observable enhancement in the microhardness of the quenched microstructure.The martensite microstructure formed after quenching in theβsingle-phase area contributes to the hardness of 512 HV.This novel alloy encompasses theβand a single-phase areas;thereby holding significant implications for the development of novel,highly deformable,and high-temperature-resistantβ-solidifyingγ-TiAl alloys characterized with fully lamellar structures.
作者
王强
李小兵
郝俊杰
陈波
张滨
张二林
刘奎
WANG Qiang;LI Xiaobing;HAO Junjie;CHEN Bo;ZHANG Bin;ZHANG Erlin;LIU Kui(Key Laboratory for Anisotropy and Texture of Materials,Education Ministry of China,School of Materials Science and Engineering,Northeastern University,Shenyang 110819,China;Ji Hua Laboratory,Foshan 528200,China)
出处
《金属学报》
北大核心
2025年第7期1060-1070,共11页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51971215
季华实验室科研项目No.X210291TL210。
关键词
β凝固γ-TiAl合金
固态相变
显微组织
凝固路径
显微硬度
βsolidifyingγ-TiAl alloy
solid-state phase transformation
microstructure
solidification pathway
microhardness
