超细晶/纳米晶γ-TiAl基合金的流变行为研究（英文）  

Flow Behavior of Ultrafine Grain/Nanocrystalline γ-TiAl Based Alloys

作　　者：陈华[1] 裴文[1] 宫学博 段振鑫 Chen Hua;Pei Wen;Gong Xuebo;Duan Zhenxin(Changchun University of Technology,Changchun 130000,China)

机构地区：[1]长春工业大学

出　　处：《稀有金属材料与工程》2019年第11期3519-3526,共8页Rare Metal Materials and Engineering

基　　金：National Natural Science Foundation of China(51371038)

摘　　要：采用高能球磨及真空热压烧结方法制备超细晶/纳米晶双相γ-Ti Al基合金。将Ti、Al、Nb单质粉末经高能球磨配制成名义成分为Ti-45Al-5Nb(原子分数,%)的纳米级混合粉末。球磨后的混合粉末经真空热压烧结(烧结温度1200℃,压力30 MPa,保温保压1 h),原位合成Ti3Al及γ-Ti Al双相等轴状合金组织,烧结组织由小于500 nm的等轴γ-Ti Al相和纳米晶Ti3Al相组成。利用Gleeble-1500D对合金进行热压缩模拟实验,变形温度为1100~1200℃、应变速率1×10^-4~1×10^-2s^-1,研究该合金压缩组织及流变行为。结果表明:与γ-Ti Al合金微米级晶粒组织相比,超细等轴双相Ti Al+Ti3Al组织明显降低了流变峰值应力,使其在2%~2.5%应变量时就达到最大,流变应力随应变速率的降低和温度的升高而降低。同时建立流变应力本构方程,反映一定条件下流变过程中材料的结构特性。结果表明,变形机制主要是在基体γ-Ti Al相中的位错和γ/γ(001)的晶间孪晶。Ultrafine grain/nanocrystalline two-phaseγ-TiAl based alloy was prepared by high energy ball milling and vacuum hot pressing sintering.Ti,Al and Nb single powders were mixed together to make the nanocrystalline powder with a nominal composition of Ti-45Al-5 Nb(at%).After ball milling,the nanocrystalline powder was sintered at the temperature of 1200℃with the pressure of 30 MPa for 1h.The sintered microstructure consisted of nanocrystallineα2-Ti3Al and the equiaxedγ-TiAl with grains less than 500nm.The hot compressive flow behavior of Ti-45Al-5 Nb alloy was studied by the Gleeble-1500 D thermal simulator at deformation temperatures of 1100,1150 and 1200℃ and strain rates of 1×10^-4,1×10^-3 and 1×10^-2s^-1.The results reveal that the peak stresses of equiaxed ultrafine microstructure are significantly lower than that of the alloys with micron-scale structure.The value of peak stress is reached at the early stage of compression(2.5%~3%strain),and the flow stress decreases with the increase of temperature and decreasing strain rate.A constitutive equation was established based on experimental data which reflects the structural characteristics of the alloy during hot deformation.It shows that the deformation mechanisms are mainly intracrystalline dislocation inγ-Ti Al phase and intergranular twins inγ/γ(001).

关 键 词：Γ-TIAL基合金 超细晶/纳米晶 热压缩 本构方程 

分 类 号：TG1[金属学及工艺—金属学]