Toward Achieving Grain Refinement in Al2014 Alloy Through Multi-pass FSP: Microstructure and Mechanical Behavior

Abstract

This study investigates the grain refinement process in Al2014 alloy through multi-pass friction stir processing (FSP) and its subsequent effects on microstructural evolution and mechanical characteristics. Optical microscopy and scanning electron microscopy were employed to study the microstructure, while mechanical characteristics were studied using a Vickers hardness tester and universal testing machine. The parent alloy showed a grain size of 98 µm, with a hardness of 147 HV, tensile strength of 456 MPa, and elongation of 17%. Through the FSP, grain size reduction was achieved with each pass, reaching 4.3 µm after the first pass, 3.9 µm after the second pass, and 4.7 µm after the third pass. Corresponding improvements in hardness, tensile strength, and elongation were observed. Hardness increased to 175 HV, 184 HV, and 171 HV after the first, second, and third passes, respectively. Tensile strength increased to 543 MPa, 559 MPa, and 532 MPa, while elongation improved to 31%, 33%, and 28% after each pass, respectively. Notably, the product of strength and elongation exhibited significant enhancements with each pass, indicating the effectiveness of the multi-pass FSP process in refining microstructures and enhancing mechanical properties.