A lightweight zero thermal expansion magnesium alloy

Area of Science:

• Materials Science
• Metallurgy
• Solid State Physics

Background:

• Thermal expansion is a critical challenge for dimensional stability in lightweight alloys.
• Low atomic mass in lightweight materials can enhance lattice vibrations, exacerbating thermal expansion issues.

Purpose of the Study:

• To develop a lightweight alloy with significantly reduced thermal expansion.
• To achieve zero thermal expansion (ZTE) in a rare-earth magnesium alloy.

Main Methods:

• A strain recovery compensation strategy was employed.
• Al-stabilized MnCoGe particles were embedded in a rare-earth magnesium alloy (1.2 vol.%).

Main Results:

• Achieved a three-orders-of-magnitude reduction in thermally induced volume change.
• Reduced the coefficient of thermal expansion from 28 × 10⁻⁶ °C⁻¹ to 0.02 × 10⁻⁶ °C⁻¹ (25-150 °C).
• The alloy exhibits ZTE, high compressive strength (424 MPa), ductility (12%), and ultralow density (1.93 g/cm³).

Conclusions:

• The ZTE behavior is attributed to sustained compressive strain from reversible martensitic transformation of embedded particles.
• This work establishes a generalizable principle for achieving thermal dimensional stability in metals using recoverable strain.
• The developed alloy offers exceptional thermal stability for lightweight systems.