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超细晶/纳米晶γ-TiAl基合金的流变行为研究
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长春工业大学材料科学与工程学院

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国家自然科学基金项目(面上项目,重点项目,重大项目)


Study on the flow behavior of ultrafine grain/ nanocrystalline γ-TiAl based alloys
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Changchun University of Technology,College of Materials Science and Engineering

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    摘要:

    摘要:本文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-TiAl基合金。将Ti、Al、Nb单质粉末经25h高能球磨配制成名义成分为Ti-45Al-5Nb(at.%) 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30MPa,保温保压1h),原位合成Ti3Al 及γ-TiAl双相等轴状合金组织,烧结组织由小于500nm的等轴γ-TiAl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10-4-10-2s-1,研究该合金压缩组织及流变行为。研究结果表明:与γ-TiAl合金微米级晶粒组织相比,超细等轴双相TiAl+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。随温度升高γ相的孪生倾向显著增加,形变主要发生在基体γ-TiAl相中,晶界滑移、位错及孪晶为等轴双相γ-TiAl合金的高温形变机制,动态回复和再结晶为其软化制。

    Abstract:

    Abstract: In this study, ultrafine grain/nanocrystalline two-phase γ-TiAl based alloy was prepared by high energy ball milling and vacuum hot pressing sintering. Ti, Al and Nb single powder were mixed together to make the nanocrystalline powder with a nominal composition of Ti-45Al-5Nb (at.%). After ball milling, the nanocrystalline powder was sintered at the temperature of 1200 °C with the pressure of 30 MPa. The sintered microstructure consisted of nanocrystalline α2-Ti3Al and the equiaxed γ-TiAl with grains less than 500 nm. The hot compressive flow behavior of Ti-45Al-5Nb alloy was studied using the Gleeble-1500D thermal simulator at deformation temperatures of 1100°C, 1150°C and 1200°C and strain rates of 1×10-4 s?1, 1×10-3 s?1and 1×10-2 s?1. The results reveal that the peak stresses of equiaxed ultrafine microstructure are significantly lower than 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 increasing 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 in γ-TiAl phase and intergranular twins in γ/γ (001).

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陈华,裴文,宫学博,段振鑫.超细晶/纳米晶γ-TiAl基合金的流变行为研究[J].稀有金属材料与工程,2019,48(11):3519~3526.[chenhua, peiwen, gongxuebo, duanzhenxin. Study on the flow behavior of ultrafine grain/ nanocrystalline γ-TiAl based alloys[J]. Rare Metal Materials and Engineering,2019,48(11):3519~3526.]
DOI:10.12442/j. issn.1002-185X.20180529

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  • 收稿日期:2018-05-23
  • 最后修改日期:2018-07-27
  • 录用日期:2018-08-08
  • 在线发布日期: 2019-12-10
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