On the Competition between Intergranular and Transgranular Failure within 7xxx Al Alloys with Tailored...

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• 7xxx aluminium alloys offer high strength but suffer from Precipitate-Free Zones (PFZs) at grain boundaries, leading to intergranular fracture and reduced ductility.
• Understanding fracture mechanisms is crucial for optimizing the formability and crashworthiness of thin aluminum sheets used in various applications.

Purpose of the Study:

• To experimentally investigate the competition between intergranular and transgranular fracture in 7075 Al alloy.
• To analyze how microstructural variations, induced by Friction Stir Processing (FSP), influence failure modes under different loading conditions.

Main Methods:

• Utilized Friction Stir Processing (FSP) to create distinct microstructures in 7075 Al alloy.
• Controlled grain structure and intermetallic (IM) particle size distribution while maintaining similar hardening precipitates and PFZs.
• Evaluated the effect of these microstructures on tensile ductility and bending formability.

Main Results:

• Microstructure significantly influenced failure modes, with differing effects on tensile ductility versus bending formability.
• An equiaxed grain structure with smaller intermetallic (IM) particles enhanced tensile ductility compared to elongated grains with larger particles.
• Conversely, the microstructure that improved tensile ductility exhibited reduced bending formability.

Conclusions:

• The study highlights a critical trade-off between tensile ductility and formability in 7075 Al alloy, dictated by microstructural characteristics.
• Tailoring grain structure and IM particle distribution through methods like FSP is essential for optimizing performance in specific applications.
• Findings are vital for enhancing the design and manufacturing of components requiring high strength and specific deformation behaviors.