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<p>Continuous variable cross-section recycled extrusion (CVCE)&#xa0;is an advanced technique of severe plastic deformation. Ti–6Al–4V alloy was deformed with different processing parameters by CVCE, and then the microstructure characterization, refinement mechanism and deformation mechanism were investigated simultaneously. The results demonstrate that the average size of grain is refined from 14 to 2.78&#xa0;μm as Ti–6Al–4V alloy is deformed at 800&#xa0;°C with a speed of 2&#xa0;mm/s over 6 passes, and the microstructure is equiaxed and distributed homogeneously along the radial direction. Furthermore, in the process of CVCE, basal slip (0001) &lt; 11 <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\overline{2 }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mn>2</mn> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> 0 &gt; is transformed to prismatic slip (10 <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\overline{1 }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mn>1</mn> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> 0) &lt; 11 <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\overline{2 }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mn>2</mn> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> 0 &gt; system and pyramidal slip (11 <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\overline{2 }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mn>2</mn> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> 2) &lt; 11 <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\overline{2 }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mn>2</mn> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> 3 &gt; system, with a reduction in low angle grain boundaries from 69.6% to 61.2%. Moreover, the grain refinement mechanism of CVCE is dislocation multiplication and cross-slip migration within the grain at the initial stage of deformation, which results in the formation of substructures and micro-shear bands as well as grain refinement. In addition, the nucleation and growth of dynamic recrystallization grains are beneficial to eliminating the dislocations, subgrain boundaries and other defects in the matrix, which finally results in the grains refinement.</p>

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Continuous variable cross-section recycled extrusion of Ti–6Al–4V alloy: microstructure evolution, deformation mechanism and refinement mechanism

  • 期刊论文

  • 发表日期：

    2026年1月24日

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  • Ying-Ying Liu,
  • Jun-Yi Zhang,
  • Fang-Lin Wu,
  • Wen-Rui Ma,
  • Ze Wu,
  • Jia-Yi Li,
  • Jiang-Bo Zhai,
  • Shi-Feng Liu,
  • Wen Wang,
  • Kuai-She Wang

摘要

Continuous variable cross-section recycled extrusion (CVCE) is an advanced technique of severe plastic deformation. Ti–6Al–4V alloy was deformed with different processing parameters by CVCE, and then the microstructure characterization, refinement mechanism and deformation mechanism were investigated simultaneously. The results demonstrate that the average size of grain is refined from 14 to 2.78 μm as Ti–6Al–4V alloy is deformed at 800 °C with a speed of 2 mm/s over 6 passes, and the microstructure is equiaxed and distributed homogeneously along the radial direction. Furthermore, in the process of CVCE, basal slip (0001) < 11 \(\overline{2 }\) 2 ¯ 0 > is transformed to prismatic slip (10 \(\overline{1 }\) 1 ¯ 0) < 11 \(\overline{2 }\) 2 ¯ 0 > system and pyramidal slip (11 \(\overline{2 }\) 2 ¯ 2) < 11 \(\overline{2 }\) 2 ¯ 3 > system, with a reduction in low angle grain boundaries from 69.6% to 61.2%. Moreover, the grain refinement mechanism of CVCE is dislocation multiplication and cross-slip migration within the grain at the initial stage of deformation, which results in the formation of substructures and micro-shear bands as well as grain refinement. In addition, the nucleation and growth of dynamic recrystallization grains are beneficial to eliminating the dislocations, subgrain boundaries and other defects in the matrix, which finally results in the grains refinement.