Ru(II) polypyridine complexes: photophysics, photochemistry, eletrochemistry, and chemiluminescence

The comprehensive body of knowledge that has built up with respect to the friction stir welding (FSW) of aluminium alloys since the technique was invented in 1991 is reviewed The basic principles of FSW are described, including thermal history and metal flow, before discussing how process parameters affect the weld microstructure and the likelihood of entraining defects After introducing the characteristic macroscopic features, the microstructural development and related distribution of hardness are reviewed in some detail for the two classes of wrought aluminium alloy (non-heat-treatable and heat-treatable) Finally, the range of mechanical properties that can be achieved is discussed, including consideration of residual stress, fracture, fatigue and corrosion It is demonstrated that FSW of aluminium is becoming an increasingly mature technology with numerous commercial applications In spite of this, much remains to be learned about the process and opportunities for further research a

Friction stir welding of aluminium alloys

Mixed Valence Complexes of d5‐d6 Metal Centers

Mixed-valence molecules: Electronic delocalization and stabilization

Publisher Summary This chapter focuses on the electron transfer reactions in organic chemistry. The simplest elementary act in homogeneous solution chemistry is the exchange of an electron between two chemical entities. No bonds need to be formed or broken in the process, and if the two species are identical, except for a difference in oxidation state, no net chemical change takes place. Such self-exchange reactions constitute the basis of theoretical treatments of electron transfer. A more complex and chemically interesting situation is the electron-transfer reaction between two species of different chemical composition. In electron-transfer theory, it is an important postulate that electrons are transferred one by one, which does not mix well with the two-electron centered electronic theory of organic molecules. Organic electron transfers rarely occur as isolated steps because of the high chemical reactivity of odd-electron species. Processes involving one or several electron-transfer steps are not likely to preserve the stereochemical integrity of the reactants. With the present upsurge of research studies frequently invoking organic electron-transfer steps in mechanistic discussions, there is a great need of a theoretical background applicable to organic species and compatible with the language of physical organic chemistry.

Electron transfer reactions in organic chemistry

Residual stress measurements in a thick, dissimilar aluminum alloy friction stir weld

Electronic Structure and Redox Properties of the Clusters [Ru3O(CH3CO2)6L3]n+

Tool wear mechanisms in friction stir welding of Ti–6Al–4V alloy

The onset of band-like properties in the ligand-bridged, trimeric cluster {[(py)2Ru3O(OAc)6(pyr)]2[Ru3O(OAc)6(CO)]}

Friction stir processing (FSP) trials were performed on 2 mm-thick Ti–6Al–4V sheets using various processing parameters including tool rotational speed (800–1000 RPM) and tool traverse speed (1–4 IPM). A processing window was established with the W–1% La 2 O 3 tool to produce defect-free friction stir processed (FSP'd) materials. The stir zone (SZ) material of the FSP'd samples showed a fully β transformed microstructure characterized by typical basket-weave lamellar α/β structure. The prior β grains in the SZs contained multiple α variants, and the average sizes ranged from 12 μm to 38 μm influenced by the processing parameters. Based on metallurgical evaluation, the microstructural evolution in different regions from base material (BM) through heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ) to SZ was established. The mechanical properties of the SZs were evaluated by tensile tests. Compared to the base material, the processed samples exhibit higher tensile strength and comparable ductility. The tensile strength was affected by the microstructure of the prior β grain size and α colony size, which are controlled by processing parameters. The lower tool rotational rate and/or higher traverse speed produced a lower peak temperature and a shorter dwell time above the β-transus temperature in the SZ, which resulted in finer prior β grains and smaller α colonies, leading to higher tensile strength.

John A. Baumann

Papers

Residual stress measurements in a thick, dissimilar aluminum alloy friction stir weld

Electronic Structure and Redox Properties of the Clusters [Ru3O(CH3CO2)6L3]n+

Tool wear mechanisms in friction stir welding of Ti–6Al–4V alloy

The onset of band-like properties in the ligand-bridged, trimeric cluster {[(py)2Ru3O(OAc)6(pyr)]2[Ru3O(OAc)6(CO)]}

Microstructure and mechanical properties of a friction stir processed Ti–6Al–4V alloy