Influence of friction stir processing on the room temperature fatigue cracking mechanisms of A356 aluminum alloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:716

Article

Nelaturu, Phalgun¹  Jana, Saumyadeep²  Mishra, Rajiv S.¹  Grant, Glenn²  Carlson, Blair E.³ 

[1] Univ North Texas, Ctr Frict Stir Proc, Dept Mat Sci & Engn, Denton, TX 76203 USA

[2] Pacific Northwest Natl Lab, Richland, WA 99352 USA

[3] Gen Motors Tech Ctr, Warren, MI 48093 USA

关键词: Fracture behavior;    Fatigue;    Grain boundaries;    Aluminum alloys;    Friction stir welding/processing;    Abnormal grain growth;   

DOI  :  10.1016/j.msea.2018.01.044

来源: Elsevier

【 摘 要 】

Failure by fatigue is a common problem associated with cast aluminum alloys due to defects like shrinkage porosities, non-metallic inclusions, etc. Friction stir processing (FSP) has recently emerged as an effective technique for local modification of microstructure. This study investigates the fatigue crack initiation and growth mechanisms in cast and FSPed A356 aluminum alloy. Two sets of parameters were used to friction stir the cast alloy resulting in the complete modification of the cast microstructure to a wrought microstructure. Both the FSPed microstructures exhibited severe abnormal grain growth (AGG) after heat treatment leading to a multimodal grain size distribution - the grain sizes ranging from a few microns to a few millimeters. One of the FSP conditions displayed an excellent improvement in fatigue life by an order of magnitude, while the other condition displayed an unexpectedly large scatter in fatigue lives. Detailed study of the fractured fatigue specimens by electron back scattered diffraction (EBSD) revealed that both, fatigue crack initiation and propagation, were intimately tied to the grain size as well as the grain misorientations in the microstructure.

【 授权许可】

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