Microstructural and Texture Evolution in Pure Niobium during Severe Plastic Deformation by Differential Speed Rolling

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Understanding microstructure evolution is crucial for optimizing material properties.
• Body-centered cubic (BCC) metals like niobium (Nb) are vital in various industrial applications.
• Severe plastic deformation techniques are explored for advanced material processing.

Purpose of the Study:

• To compare the microstructural and textural evolution of BCC Nb processed by conventional rolling and high-ratio differential rolling (HRDSR) at room temperature.
• To investigate the effectiveness of continuous dynamic recrystallization (CDRX) under different rolling conditions.
• To analyze the resulting tensile strength and strengthening mechanisms in HRDSR-processed Nb.

Main Methods:

• Conventional rolling and high-ratio differential rolling (HRDSR) at room temperature.
• Microstructural analysis to observe grain refinement and recrystallization.
• Texture analysis to study the development of crystallographic orientations (α-fiber and γ-fiber).
• Tensile testing to determine mechanical properties and strengthening mechanisms.

Main Results:

• HRDSR resulted in more effective grain refinement via continuous dynamic recrystallization (CDRX) compared to conventional rolling, though overall refinement was limited.
• CDRX preferentially occurred on {111} γ-fiber grains over {001}<110> α-fiber grains.
• HRDSR processing led to weaker α-fiber and stronger γ-fiber textures, indicating shear deformation's influence.
• HRDSR-processed Nb exhibited a high tensile strength of 450 MPa, primarily due to dislocation-density strengthening at large thickness reductions.

Conclusions:

• HRDSR is a promising technique for refining BCC Nb microstructure and enhancing its mechanical properties.
• The observed texture evolution under HRDSR highlights the role of shear deformation in texture development.
• Dislocation-density strengthening is the dominant mechanism for enhancing the tensile strength of severely deformed Nb through HRDSR.