Ultrasonic spot welding of a clad 7075 aluminum alloy: Strength and fatigue life

[Display omitted] •The “unweldable” Al7075 alloy is successfully welded with a clad layer via USW.•Clad layer of AA7072 alloy contributes to the defect-free sound welded joints.•Tensile lap shear strength exceeds AWS D17.2 standards at higher energy levels.•The solid-state ultrasonic spot welded joi...

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Bibliographic Details
Published in:International journal of fatigue 2020-12, Vol.141, p.105869, Article 105869
Main Authors: Mohammed, S.M.A.K., Jaya, Y.D., Albedah, A., Jiang, X.Q., Li, D.Y., Chen, D.L.
Format: Article
Language:English
Subjects:
AA7072 clad
AA7075
Aluminum base alloys
Bonded joints
Cyclic loads
Dimpling
Dynamic recrystallization
Energy levels
Failure mechanisms
Fatigue
Fatigue failure
Fatigue life
Grain refinement
Heat treating
Materials fatigue
Mechanical properties
Metal fatigue
Shear strength
Spot welding
Striations
Tensile lap shear strength
Ultrasonic spot welding
Ultrasonic testing
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Summary:[Display omitted] •The “unweldable” Al7075 alloy is successfully welded with a clad layer via USW.•Clad layer of AA7072 alloy contributes to the defect-free sound welded joints.•Tensile lap shear strength exceeds AWS D17.2 standards at higher energy levels.•The solid-state ultrasonic spot welded joints exhibit superior fatigue resistance.•Depending on cyclic load levels, two types of fatigue failure modes are observed. The purpose of this study was to examine weldability of an AA7072-cladded high-strength AA7075-T6 via ultrasonic spot welding, focusing on the influence of welding energy on mechanical properties and failure mechanisms. Defect-free sound joints were achieved with robust bonding and grain refinement via dynamic recrystallization at the weld interface, leading to superior static and fatigue properties. The nominal tensile lap shear strength increased with increasing welding energy, and exceeded AWS D17.2 standards at higher energy levels. Interfacial failure at higher cyclic loads with distinctive elongated shear dimples and fatigue striations and transverse through-thickness failure at lower cyclic loads were observed.
ISSN:0142-1123
1879-3452
DOI:10.1016/j.ijfatigue.2020.105869