Strong, ductile, and hierarchical hetero-lamellar-structured alloys through microstructural inheritance and...

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• The ubiquitous strength-ductility trade-off limits material performance, particularly in brittle intermetallic-containing multiple principal element alloys (MPEAs).
• Hierarchical heterogeneities offer a microstructural solution for simultaneous strength and ductility enhancement.
• Conventional methods for creating hierarchical heterostructures are often costly and time-consuming.

Purpose of the Study:

• To develop an efficient and low-cost strategy for overcoming the strength-ductility trade-off in MPEAs.
• To design and implement a multiscale microstructural inheritance and refinement approach.
• To achieve superior mechanical properties in Al_0.7CoCrFeNi MPEAs through a novel hierarchical hetero-lamellar structure (HLS).

Main Methods:

• Processing of "structural hierarchy precursors" in as-cast heterogeneous Al_0.7CoCrFeNi MPEAs.
• Simple rolling and annealing to form a hierarchical hetero-lamellar structure (HLS).
• Rapid annealing (10 minutes) to achieve desired microstructural features and properties.

Main Results:

• A hierarchical hetero-lamellar structure (HLS) was successfully created in Al_0.7CoCrFeNi MPEAs.
• Record-high strength-ductility combinations were achieved with significantly reduced processing time.
• The HLS design triggered unusual deformation mechanisms, including profuse dislocations and stacking faults, leading to sustained strain hardening and extrinsic ductilization.

Conclusions:

• The proposed microstructural inheritance and refinement strategy provides an efficient, fast, and low-cost approach to overcome the strength-ductility trade-off.
• This method is applicable to a broad range of structural materials.
• The hierarchical HLS design enables multiple unusual deformation and reinforcement mechanisms for enhanced mechanical performance.