Surface composites by friction stir processing: A review

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

The friction stir welding (FSW) technique is widely accepted to be one of the most significant welding techniques to emerge in the last 20 years. Friction stir welding of Al-alloys is now commonplace and is covered in several recent reviews, including one in this journal. Consequently, the technique is currently being used for joining of these alloys in various industrial applications. Complementary to these developments has been a dramatic increase in research into joining of other alloys and systems by FSW. This field is very active, but less mature. Thus, the aim of this review article is to build on our understanding of the fundamentals, as applied to Al-alloys that laid out in the previous review in this journal, and to address the current state-of-the-art of FSW developing beyond Al-alloys, including Mg-alloys, Cu-alloys, steels, Ti-alloys and metal matrix composites, focusing particularly on microstructural aspects, including texture formation, and the resulting properties of these joints. ...

Friction stir welded structural materials: beyond Al-alloys

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

Friction stir based welding and processing technologies - processes, parameters, microstructures and applications: A review

Butt joints of 1060 aluminum alloy and commercially pure copper were produced by friction stir welding (FSW) and the effect of welding parameters on surface morphology, interface microstructure and mechanical properties was investigated. The experimental results revealed that sound defect-free joints could be obtained under larger pin offsets when the hard Cu plate was fixed at the advancing side. Good tensile properties were achieved at higher rotation rates and proper pin offsets of 2 and 2.5 mm; further, the joint produced at 600 rpm with a pin offset of 2 mm could be bended to 180 degrees without fracture. The mechanical properties of the FSW Al-Cu joints were related closely to the interface microstructure between the Al matrix and Cu bulk. A thin, uniform and continuous intermetallic compound (IMC) layer at the Al-Cu butted interface was necessary for achieving sound FSW Al-Cu joints. Stacking layered structure developed at the Al-Cu interface under higher rotation rates, and crack initiated easily in this case, resulting in the poor mechanical properties. (C) 2011 Elsevier B.V. All rights reserved.

Effect of friction stir welding parameters on the microstructure and mechanical properties of the dissimilar Al-Cu joints

Aluminum and copper plates were successfully friction stir welded by offsetting the tool to the aluminum side, producing excellent metallurgical bonding on the Al-Cu interface with the formation of a thin, continuous and uniform Al-Cu intermetallic compound (IMC) layer. Furthermore, many IMC particles were generated in the nugget zone, forming a composite structure. Tensile tests indicated that the FSW joint failed in the heat-affected zone of the aluminum side with the Al-Cu interface bonding strength being higher than 210 MPa. (C) 2010 Elsevier B.V. All rights reserved.

Enhanced mechanical properties of friction stir welded dissimilar Al–Cu joint by intermetallic compounds

Low tensile ductility owing to the insufficient strain hardening is the main drawback for ultrafine-grained (UFG) materials, which restricts their practical applications. Here, via a simple friction stir processing technique with additional cooling, we prepared UFG Cu with high strength and tensile ductility. Enhanced strain hardening capacity, which is effective in blocking and accumulating dislocations, was achieved in the present recrystallized UFG microstructure. The enhanced strain hardening capacity is attributed primarily to the low dislocation density, and the presence of large fraction of high angle grain boundaries and a certain amount of coherent twin boundaries. This work provides a strategy for designing UFG materials with good mechanical properties. (C) 2011 Elsevier B.V. All rights reserved.

High tensile ductility via enhanced strain hardening in ultrafine-grained Cu

Aluminium and copper plates with 3 mm thickness were successfully friction stir lap welded at a lower rotation rate of 600 rev min 21 using a larger pin 8 mm in diameter. Good metallurgical bonding on the Al/Cu interface was achieved due to the formation of a thin, continuous and uniform Al-Cu intermetallic compound layer. Furthermore, many Cu particles consisting of pure Cu and intermetallic compound layers were generated at the lower part of the nugget zone, forming a composite structure with increased hardness. A lower rotation rate resulted in a decrease in annealing softening in the heat affected zone (HAZ), and a larger diameter pin increased the Al-Cu bonding area. These factors resulted in that the friction stir welded lap joint exhibited a high failure load of 2680 N with failure in the HAZ on the aluminium side.

Achieving high property friction stir welded aluminium/copper lap joint at low heat input

As-cast Cu–9Al–4.5Ni–4Fe NiAl bronze (NAB) alloy was subjected to friction stir processing (FSP) in a wide range of tool rotation rates of 800–2000 rpm and traverse speeds of 50–200 mm/min. After FSP, the initial coarse microstructure of the as-cast NAB was transformed to fine structure, and the porosity defects were eliminated. However, the stir zones were characterized by inhomogeneous structure and could be divided into four regions: fine Widmanstatten primary α phase in the surface layer, banded primary α and β′ phases in the subsurface layer, equiaxed α and β′ phases in the center, and streamlike α and β′ phases at the bottom. The heterogeneous microstructure could be alleviated by adjusting the FSP parameters, but could not be completely eliminated under investigated FSP parameters. The FSP NAB exhibited significantly improved hardness, tensile strength, and ductility compared to the base metal. When the NAB was subjected to two pass FSP, its microstructure was further homogenized, resulting in apparently increased ductility with similar hardness and tensile strength.

P. Xue

Papers

Effect of friction stir welding parameters on the microstructure and mechanical properties of the dissimilar Al-Cu joints

Enhanced mechanical properties of friction stir welded dissimilar Al–Cu joint by intermetallic compounds

High tensile ductility via enhanced strain hardening in ultrafine-grained Cu

Achieving high property friction stir welded aluminium/copper lap joint at low heat input

Inhomogeneous microstructure and mechanical properties of friction stir processed NiAl bronze