Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

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Friction Stir Welding and Processing

Perspectives on Titanium Science and Technology

Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

A review of dynamic recrystallization phenomena in metallic materials

The Effect of Ni Content on the Isothermal Character of Lath Martensitic Transformation in Fe-Ni Alloys

When a polycrystalline material is deformed, each grain must satisfy the continuity of stress and strain at grain boundaries during deformation. It is called constraint'' by grain boundaries. It has been thought that the constraint affects the deformation behavior of grains, such as crystal rotation and deformed microstructure. However, the details of the effect, particularly the initial orientation dependence, have not been clarified sufficiently. It is well known that in the (001)[100] single crystals in Fe-Si alloys or in iron the matrix bands'' are formed by rolling. The matrix bands are composed of the banded regions which are rotated toward (001) orientation either clockwise or counterclockwise. However, the matrix bands in (001)[100] crystals have not been reported in polycrystalline materials. Although there have been many investigations on the matrix bands in the (001)[100] single crystals, no information as to how the constraint affects the rolled microstructure of the crystals is available. The purpose of the present study is to clarify the effect of the constraint on the rolled microstructure of the (001)[100] oriented single crystal in an Fe-19%Cr ferritic alloy.

Effect of constraint on the rolled microstructure of (001)[100] oriented single crystals in an Fe-19%Cr ferritic alloy

The crystallography of lath martensite formed at austenite grain boundaries in Fe-Ni-Mn alloy

An alloy with a shape memory effect and a pseudo-elasticity which exhibits a thin-plate martensitic structure and consists of 32-34 wt.% of nickel, 3-6 wt.% of titanium, 10-15 wt.% of cobalt and the remainder of iron can be made by heating a starting alloy to a temperature between 900°C to 1,200°C and then aging at a temperature between 500°C and 800°C.

Tadashi Maki

Papers

The Effect of Ni Content on the Isothermal Character of Lath Martensitic Transformation in Fe-Ni Alloys

Effect of constraint on the rolled microstructure of (001)[100] oriented single crystals in an Fe-19%Cr ferritic alloy

The crystallography of lath martensite formed at austenite grain boundaries in Fe-Ni-Mn alloy

Iron-nickel-titanium-cobalt alloy with shape memory effect and pseudo-elasticity, and method of producing the same

Formation Temperature and Growth Behaviour of Thin Plate Martensite in Fe-Ni-C Alloys