Mechanical Behavior of a Medium-Entropy Fe₆₅(CoNi)₂₅Cr_9.5C_0.5 Alloy Produced by Selective Laser Melting

Area of Science:

• Materials Science
• Metallurgy
• Additive Manufacturing

Background:

• Medium-entropy alloys (MEAs) offer tunable properties for advanced applications.
• Additive manufacturing (AM) enables complex alloy designs but requires optimization for mechanical performance.
• Understanding the influence of processing on microstructure and mechanical behavior is crucial for alloy development.

Purpose of the Study:

• To investigate the microstructure and mechanical properties of a novel FeCoNiCr-based medium-entropy alloy produced by selective laser melting (SLM).
• To evaluate the alloy's performance at cryogenic and room temperatures, focusing on the role of the transformation-induced plasticity (TRIP) effect.

Main Methods:

• Selective laser melting (SLM) was employed to fabricate Fe65(CoNi)25Cr9.5C0.5 alloy specimens.
• Tensile testing was conducted at room temperature (approx. 293 K) and cryogenic temperature (77 K).
• Microstructural analysis was performed to correlate structure with mechanical behavior.

Main Results:

• SLM produced a high-density alloy (<0.5% porosity) with an elongated substructure and ~300 nm cells.
• At 77 K, the alloy showed high yield strength (680 MPa) and ultimate tensile strength (1800 MPa) with 26% elongation, attributed to a pronounced transformation-induced plasticity (TRIP) effect.
• At room temperature, the TRIP effect was less significant, resulting in lower strain hardening and YS/UTS of 560/640 MPa.

Conclusions:

• The FeCoNiCr-based medium-entropy alloy fabricated by SLM exhibits excellent mechanical properties at cryogenic temperatures, driven by the TRIP effect.
• The study highlights the potential of SLM for producing high-performance alloys with tailored microstructures.
• Further investigation into deformation mechanisms can optimize alloy design for specific temperature regimes.