An isotropic zero thermal expansion alloy with super-high toughness

Area of Science:

• Materials Science
• Metallurgy
• Solid State Physics

Background:

• Zero thermal expansion (ZTE) alloys are critical for applications requiring dimensional stability.
• Achieving both ZTE and high mechanical properties simultaneously in multicomponent alloys remains a significant challenge.

Purpose of the Study:

• To develop a multicomponent alloy that combines near-zero thermal expansion with superior mechanical toughness.
• To investigate the underlying mechanisms responsible for the dual functionality in a heterogeneous alloy system.

Main Methods:

• Synthesis and characterization of a novel LaFeCoSi alloy.
• Analysis of the alloy's thermal expansion properties using dilatometry.
• Evaluation of mechanical properties, specifically toughness, through experimental testing.
• Investigation of the material's microstructure and phase composition using advanced analytical techniques.

Main Results:

• A near-isotropic zero thermal expansion (α_l = 1.10 × 10^-6 K^-1 between 260-310 K) was achieved in the LaFe₅₄Co_3.5Si_3.35 alloy.
• The alloy demonstrated exceptionally high toughness (277.8 ± 14.7 J cm^-3).
• Chemical partitioning within the dual-phase structure was identified as key to modulating thermal expansion via magnetic interactions and enhancing mechanical properties through interface bonding.

Conclusions:

• The synergistic enhancement across lattice, phase interfaces, and heterogeneous structure is crucial for achieving high toughness.
• This work provides a pathway for designing multicomponent alloys with tailored thermal expansion and prominent mechanical properties for ultra-stable functional materials.