Effect of Friction Stir Welding on microstructure and mechanical properties of uns C19400 alloy plates

Abstract

The welding of metallic materials by the Friction Stir Welding (FSW) method is a very attractive process for preserving their characteristics, especially for copper and its alloys that require high heat input and present many distortions by traditional methods. However, it is a great challenge to produce welds free of defects and maintain or improve their mechanical properties. In the current literature data on FSW parameters for copper and its alloys are scarce. In this study, tests were performed with a combination of four tool rotations (750, 850, 950, 1050 rev.min-1) and two welding speeds (20 and 60 mm.min-1), maintaining the tool inclination angle in 3° and waiting time of 5 seconds. The objective of this work is to analyze the microstructure and mechanical performance of lap joints of the UNS C19400 alloy joined by FSW. The process temperature was monitored to trace the heating profile of the process, in addition to microhardness and shear strength tests, in addition to optical microscopy for analysis. The joints welded by the parameters Ω 950 rev.mm-1 𝛖 20mm.min-1 obtained a mechanical performance of 73% compared to the characteristics of the base metal and despite the appearance of volumetric defects at the microstructural level, the metallurgical transformations of recovery and recrystallization of the grains observed in the microstructure played a key role in the result.