Mode I Fracture Behavior of 6061 Aluminum Alloy Processed by Friction Stir Processing

Crack nucleation mechanisms, its growth, and the determination of critical failure parameters are of industrial importance. Therefore, it is inevitable to study the mechanical behavior of cracked materials under applied load during severe plastic deformation. The present study studied the mode I fracture behavior, mechanical properties, and microstructure characterization of the 6061 aluminum alloy fabricated by friction stir processing (FSP). For this purpose, a milling machine made a perfect stirring zone to perform the FSP method with the specific non-consumable tool. According to the tensile test results, the yield and ultimate tensile strength of the FSP-processed sample have increased by 39% and 37%, respectively. Based on the three-point bending test, the fracture toughness of the processed aluminum was calculated as 10.86 MPa√m, which shows a 14.3% improvement compared to the as-received annealed state. Eventually, the average grain size of the annealed and processed samples was measured as 35 and 15, respectively, which indicated a 57% reduction in the aluminum grain size after FSP. Note that this grain refinement is associated with improved strength and toughness.