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Construction of bimodal-grained Mg-Bi alloy composed of ultrafine grains and fine grains and its strengthening and toughening mechanisms
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国家自然科学基金资助(52265048);甘肃省科技重大专项(22ZD6GA008);甘肃省高等学校创新项目(2022A-025);中国博士后科学基金(2022M713656);温州市级科技计划项目(G2023018);甘肃省青年科技基金计划(21JR7RA261);兰州理工大学红柳优秀青年基金人才支持计划(062205)

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    Abstract:

    Low-temperature equal channel angular pressing (ECAP) processing technology has great potential in fabricating bimodal-grained alloys composed of ultrafine grains and fine grains. Besides, fine grain Mg-Bi based alloys demonstrate excellent low temperature plastic deformation performance. Based on this, a new inverse temperature field ECAP (ITF-ECAP) processing method was developed to realize the severe plastic processing of a fine grained Mg-6Bi (B6) alloy at low temperature (<100 ℃) to construct a bimodal-grained microstructure composed of ultrafine (<1 μm) and fine grains (1-10 μm). The microstructure and mechanical properties characterization results show that dynamic recrystallization preferentially occurred at the initial grain boundaries of the fine-grained B6 alloy during the multi pass ITF-ECAP processing. Besides a large amount of submicron sized Mg3Bi2 phase precipitated during ITF-ECAP processing. As a result, bimodal-grained microstructure consisting of ultrafine grains with an average grain size (AGS) of about 600 nm and fine grain region with an AGS of about 2 μm was successfully constructed in B6 alloy through 4-pass ITF-ECAP processing. The volume fraction of the ultrafine grain region accounts for about 72.5 %. Due to the combined effects of grain-boundary strengthening, precipitation strengthening, dislocation strengthening, and back stress strengthening, the bimodal-grained B6 alloy exhibits excellent strength and ductility, with yield strength and elongation reaching 315.6±3.6 MPa and 22.3±1.0 %, respectively.

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[mengshuaiju, songjinlong, chenkeyi, cuimin, wanglidong, biguangli, caochi, yangguirong. Construction of bimodal-grained Mg-Bi alloy composed of ultrafine grains and fine grains and its strengthening and toughening mechanisms[J]. Rare Metal Materials and Engineering,,().]
DOI:10.12442/j. issn.1002-185X.20240480

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History
  • Received:August 02,2024
  • Revised:September 18,2024
  • Adopted:September 27,2024
  • Online: November 21,2024
  • Published: