Microstructural Evolution and Mechanical Properties in Superlight Mg-Li Alloy Processed by High-Pressure Torsion

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Magnesium-lithium (Mg-Li) alloys are lightweight materials with potential applications in various industries.
• Understanding microstructural evolution and mechanical properties is crucial for optimizing alloy performance.
• High-pressure torsion (HPT) is a severe plastic deformation technique used for grain refinement.

Purpose of the Study:

• To investigate the microstructural changes in LZ91 Mg-Li alloy after high-pressure torsion (HPT) processing.
• To evaluate the mechanical properties, including microhardness and tensile elongation, of the processed alloy.
• To correlate microstructural evolution with observed mechanical property enhancements.

Main Methods:

• High-pressure torsion (HPT) processing at ambient temperature for up to 10 turns.
• Microstructural analysis using optical microscopy and X-ray diffraction (XRD).
• Microhardness testing and micro-tensile testing at various temperatures (298 K to 473 K).

Main Results:

• Significant grain refinement from 30 μm to approximately 230 nm was achieved after 10 HPT turns.
• LZ91 alloy retained its α (hcp) and β (bcc) phases throughout HPT processing.
• Microhardness increased with the number of HPT turns, attributed to Hall-Petch strengthening.
• Ultra-fine grain LZ91 Mg-Li alloy exhibited excellent tensile elongation of ~400% at 473 K.

Conclusions:

• HPT processing effectively refines the microstructure of LZ91 Mg-Li alloy, leading to enhanced microhardness.
• The alloy maintains its dual-phase structure after severe plastic deformation.
• The ultra-fine grained LZ91 Mg-Li alloy shows promising high-temperature mechanical properties, particularly in terms of ductility.