Exploiting low levels of rare earth addition in Mg extrusion alloys

The present work examines the extrusion and mechanical properties of MExlOO alloys, which contain levels of rare earth alloying additions up to 0.4 wt%. It is shown that these alloys can display the high extrudability of alloy Ml with strengths nearing those of AZ31. Most importantly, the grades display high room temperature ductility; values of total tensile elongation as high as 30% have been observed. These benefits derive from a combination of grain refinement and texture weakening.

The role of strain on the recrystallization behaviour of hot worked and annealed magnesium alloy Mg-3Al-1Zn

The present work examines the microstructure that evolves during the hot deformation and subsequent annealing of magnesium alloy AZ31. In particular, the role of strain on the progression of dynamic recrystallization (DRX) and post-deformation recrystallization is investigated. It is found that the grain size developed after post-deformation recrystallization is larger when the deformation strain, and hence the degree of DRX, is low (for strains up to 0.4). Also, the kinetics of post-deformation recrystallization are found to be independent of strain for strain values of 0.4 and above. Whilst increasing strain alters the texture of the un-recrystallized microstructure (for the deformation mode examined), the texture does not change significantly during post-deformation recrystallization.

On the impact of second phase particles on twinning in magnesium alloys

Deformation twinning is an important deformation mode in magnesium alloys. Despite this, little is known on the extent to which the stress for twinning can be altered by a dispersion of second phase particles. The current paper presents a series of findings on the role of differently shaped particles on both the stress required for twinning and the characteristics of the twins that form. It is shown that plate shaped particles are, as one might expect, an effective strengthener to {10-12} twinning. When precipitate plates form on the basal planes, the relative hardening of basal slip is minor in comparison to that seen for twinning. This provides opportunity for the alloy designer to control the apparent critical resolved shear stresses (CRSS) for the different deformation modes. Possible sources for the hardening of twins are discussed.

Initial public offerings of energy companies

This study analyses 158 energy company initial public offerings (IPOs) in Australia from January 1994 to December 2010, including the period of the global financial crisis (GFC). The study finds that energy company IPOs had an average 22.0 % underpricing and that those IPOs that sought to raise more equity capital and engaged underwriters had lower underpricing. There is also evidence that suggests energy company IPOs that offered options to their underwriters had higher underpricing returns, effectively cancelling the lower underpricing effect of the underwriting itself. The energy IPOs that raised equity capital after the 2007/8 global financial crisis do not appear to have offered on average, significantly different underpricing returns to their investors compared to those energy IPOs that raised capital prior to this GFC period. The findings of this study offer insights for issuers who seek to lower underpricing, for underwriters involved in the capital raising and for investors who are looking to invest in Australian energy company IPOs.

Effect of Zn concentration and grain size on prismatic slip in Mg-Zn binary alloys

Mg-Zn binary alloys with concentrations between 0 and 2.8wt% Zn have been prepared and processed via hot rolling and annealing to produce specimens with a strong basal texture and a range of grain sizes. These have been deformed in tension, a condition in which the deformation is dominated by prismatic slip. This data has been used to assess the Hall-Petch parameter as a function of Zn concentration for deformation dominated by prismatic slip. Pure magnesium showed non-linear Hall-Petch behaviour at large grain sizes, and this is compared to the values for prismatic slip measured on single crystals. The differences between critical resolved shear stress measurements made through single crystal, polycrystal and mathematical modelling techniques are also discussed.

Aid allocation and fragile states

This chapter summarizes research on aid allocation and effectiveness, highlighting the current findings of recent research on aid allocation to fragile states. Fragile states are defined by the donor community as those with either critically poor policies or poorly performing institutions, or both. The chapter examines the research findings in the broader context of research and analysis on how aid should and is being allocated across all developing countries. Various aid allocation models and their implications for aid to fragile states are considered. The chapter also looks at types of instruments and their sequencing in fragile states.