Friction stir welding/processing of metals and alloys: A comprehensive review on microstructural evolution

Recent progress on control strategies for inherent issues in friction stir welding

At present aluminium-magnesium alloys are widely used in various engineering applications due to its light weight and superior properties. Joining is considered as one of the most complex phenomenon in various precision industries like aerospace, railway, automotive and marine structures because inflexible tolerances are required during different product assembly. The friction stir welding (FSW) of aluminium-magnesium of various grade has incited substantial scientific and industrial importance since it has a potency to transform the product with a good quality joint. The fabrication of such alloys is a challenging task through conventional fusion welding due to its various metallurgical concerns. Therefore, the present work is intended to summarize the recent progress in FSW of aluminium-magnesium alloys. Particular attention has been paid to microstructural evolution, phase transformation, recrystallization mechanism, material flow behaviour and how the process parameters influence the various mechanical properties and associated defects during FSW. Various experimental and numerical simulation results have been mentioned for weld property comparison. Finally, this work not only points out the prominent conclusions of the preceding research but also recommends the upcoming guidance concerning to fabrication of aluminium-magnesium alloys through FSW.

Recent research progress in solid state friction-stir welding of aluminium–magnesium alloys: a critical review

The paper critically assesses the research progress towards aluminium–magnesium dissimilar friction stir welding (FSW). First, the theoretical requirements are explored through the understanding of joining mechanism and heat generation in aluminium–magnesium FSW. Next, the observed trends in microstructural characterisation and mechanical properties are analysed. Finally, the effects of welding parameters and how it influences process variables and materials responses are discussed in detail, and several suggestions are made based on these discussions.

Review of research progress on aluminium–magnesium dissimilar friction stir welding

Conventional and cooling assisted friction stir welded Al–Mg joints were investigated by visual inspection, optical macro plus microscopy, scanning electron micrographs, energy dispersive X-ray spectroscopy, X-ray diffractions, tensile testing and micro hardness indentation. The nugget zone is characterized by onion rings composed of different phases such as Mg in an Al matrix, Al in an Mg matrix as well as intermetallic compounds, Al3Mg2 and Al12Mg17. A diffusion layer was detected on the Al side of the joint between the nugget and thermo-mechanically affected zones identifying a solid solution of Mg in Al. No diffusion layer was observed on the Mg side. The tensile strength of the dissimilar joints is enhanced by cooling assisted welding process due to the reduction in the amount of intermetallic compounds inside the weld bead. Congruently, higher hardness peaks are reported in the nugget zone of conventional FSW joint with respect to the CFSW joint.

Conventional and cooling assisted friction stir welding of AA6061 and AZ31B alloys

Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg Dissimilar Friction Stir Welding Joints

This work was performed under contract DE-FE-0031631 for the project entitled “ICME for Advanced Manufacturing of Ni Superalloy Heat Exchangers with High Temperature Creep + Oxidation Resistance for Supercritical CO2” supporting the U.S. Department of Energy’s Area of Interest “Computational Tools to Support Advanced Manufacturing of Fossil Energy Technologies.” The project was structured around the development of an integrated computational materials engineering (ICME) framework for the multi-physics modeling of creep oxidation, and its implementation for Haynes® alloys HR-224, 282 (UNS N07208, referred to herein as H282) and a hybrid material construction constituted as a bilayer of both materials. 

Taiwu Yu

Papers

Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg Dissimilar Friction Stir Welding Joints

ICME for Advanced Manufacturing of Ni Superalloy Heat Exchangers with High Temperature Creep + Oxidation Resistance for Supercritical CO2