Effect of Process Parameters on the Microstructure and Mechanical Properties of Friction Stir Welded Copper-MWCNT Joints

Abstract

The main objective of this study is to investigate the influence of the tool rotation speed (TRS) and tool traverse speed (TTS) on the microstructure, microhardness and the tensile strength of the copper – MWCNT welded joints. MWCNT particles were successfully incorporated in the weld zone of the copper plate through the holes drilled at the sides of the abutting copper plates. The joints were welded using a tool with tapered cylindrical pin profile. The TRS was varied between 1200 and 1300 rpm. The TTS was varied between 50 mm/min and 100 mm/min. The parametric limits were fixed based on the trial runs conducted for obtaining defect free welds. The defect free welds were evaluated for microhardness in the nugget zone as per ASTM E384. The tensile strength of the joints was tested as per ASME Section IX-2019. Microstructural investigations revealed the formation of intercalated banded structures indicating homogeneous mixing and distribution of MWCNTs in the copper matrix. Maximum tensile strength of 175 MPa was achieved for the joint fabricated with 1200 rpm TRS and TTS of 30 mm/min. Weldment with maximum microhardness of 100.21 Hv was achieved for the same combination of process parameters. The sample processed at a higher TRS of 1300 rpm and lower TTS of 20 mm/min yielded the second best tensile and microhardness. The tensile strength of the welded joints was observed to increase with increasing the TTS and the TRS.