Solid state recycling of 5083 Al alloy by hot extrusion

The machined chips of 5083 Al alloy were recycled by hot extrusion at 723 K with an extrusion ratio of 44:1 in air. Corrosion and mechanical properties of the recycled specimens have been compared with those of a virgin extrusion which was processed from the ingot block. As a result of salt immersion tests, mass loss of the recycled specimen was not less than twice of that of the virgin extrusion. The deterioration in corrosion properties for the recycled specimen was attributed to the excessive contamination of Fe which promoted galvanic corrosion. As a result of tensile tests, the recycled specimen exhibited a good combination of high strength and high elongation to failure at room temperature. The excellent mechanical properties for the recycled specimen were attributed to the refined microstructure. However, the elongation to failure of the recycled specimen at elevated temperatures more than 573 K was lower than that of the virgin extrusion. The contamination of oxide particles is likely to be responsible for the lower elongation in the solid recycled specimen.

Evolution of hot working stress and microstructure of Mg-3Al-1Zn

The deformation behaviour of magnesium alloy AZ31 was examined. The work found that dynamic recrystallisation operates during hot deformation. The influence that different process variables have on this mechanism were quantified. The optimisation of dynamic recrystallisation allows magnesium alloys to be formed into products more easily whilst developing enhanced final properties.

Evolution of recrystallization during and following hot deformation

Recrystallization of austenite during and following hot deformation has been studied in detail in a type 304 austenitic stainless steel. Furthermore, the effect of second phase on the softening process of austenite has been investigated using a 2205 duplex stainless steel. The mechanical and microstructural features have been compared for dynamic and post deformation recrystallization.

Determination of resin acids in pulp mill effluent and receiving waters by high performance liquid chromatography

Resin acids are reported to be of major toxicological importance in pulp mill effluents for Rainbow Trout. Their determination, using a high performance liquid chromatographic method, is described.

Variant selection during the c-to-ab phase transformation in hot-rolled bainitic TRIP-aided steels

The variant selection phenomenon during the austenite to bainite phase transformation in hot-rolled TRIP-aided steels was quantitatively characterized at the level of individual austenite grains. The reconstruction of the electron backscatter diffraction maps provided evidence that bainite grows by packets of laths sharing a common {1 1 1}_y plane in the austenite. The affect of hot deformation is to reduce the number of packets that form. It is suggested that slip activity is important in understanding this effect.

Performance of building integrated solar hot water systems

The integration of solar energy systems into buildings has been the subject of considerable commercial and academic research, particularly building integrated photovoltaics. However, the integration of solar hot water systems into roofing systems has had far less attention. This paper presents the theoretical and experimental results of a novel building integrated solar hot water system developed using existing long run roofing materials.

This work shows that it is possible to achieve effective integration that maintains the aesthetics of the building and also provides useful thermal energy. The results of an unglazed 108m2 swimming pool heater and 8m2 glazed domestic hot water systems are presented.

The experimental results show that the glazed system performs close to the theoretical model and is an effective provider of hot water in certain climates. However it was also found that for larger scale building integrated solar water heating systems, special attention must be paid to the configuration and arrangement of the collectors in order to minimise problems with respect to flow distribution and its effect on collector and system efficiency.

Microscale modelling of AISI 304 behaviour during hot deformation

This project aimed to model the microstructure evolution during and following hot deformation using a cellular automaton approach. The flow curves, softening kinetics and final microstructures were used as the input data for the post-deformation simulation to elucidate the effect of dynamic recrystallization on the post-deformation softening.

Underpricing, risk management, hot issue and crowding out effects : evidence from the Australian resources sector initial public offerings

The main purpose of this paper is to explore the role of risk management, speculative industry competition effect and hot issue markets. We used a sample of 260 initial public offerings (IPOs) in the Australian resource sector for the 1994–2004 period to test the underpricing effect. We do not find any evidence that risk management can reduce the uncertainty relating to the new issue and hence alleviate the extent of underpricing. A plausible explanation for this lack of evidence is the poor information content of publicly available disclosures regarding risk management activities of IPO firms. We further provide evidence that the underpricing returns for resources IPOs are not impacted upon by the strength of alternative speculative IPO markets. We also show that the degree of underpricing adjusts to both market return in the preceding three months and the average underpricing of resources IPOs in the 12 month period leading to the float which offers an explanation to the hot issue effect observed in the IPO market.

Corporate commitment to sustainability – is it all hot air? A review of the linkage between executive pay and sustainable performance

Across time, companies are increasingly making public commitments to sustainable development and to reducing their impacts on climate change. Management remuneration plans (MRPs) are a key mechanism to motivate managers to achieve corporate goals. We review the MRPs negotiated with key management personnel in a sample of large Australian carbon-intensive companies. Our results show that, as in past decades, the companies in our sample have MRPs in place that continue to fixate on financial performance. We argue that this provides evidence of a disconnection between the sustainability-related rhetoric of the sample companies, and their ‘real’ organisational priorities.

The effect of skin passing on the material behavior of metal strip in pure bending and tension

The metal strip used in roll forming has often been preprocessed by (tension or roller) leveling or by skin-pass rolling, and as a consequence, may contain residual stresses. These stresses are not well observed by the tensile test, but could have a significant effect on the bending and springback behavior. With the advent of improved process design techniques for roll forming, including advanced finite element techniques, the need for precise material property data has become important. The major deformation mode of roll forming is that of bending combined with unloading and reverse bending, and hence property data derived from bend tests could be more relevant than that from tensile testing.

This work presents a numerical study on the effect of skin passing on the material behavior of stainless steel strip in pure bending and tension. A two dimensional (2-D) numerical model was developed using Abaqus Explicit to analyze the affect of skin passing on the residual stress profile across a section for various working conditions. The deformed meshes and their final stress fields were then imported as pre-defined fields into Abaqus Standard, and the post-skin passing material behavior in pure bending was determined. The results show that a residual stress profile is introduced into the steel strip during skin passing, and that its shape and stress level depend on the overall thickness reduction as well as the number of rolling passes used in the skin passing process. The material behavior in bending and the amount of springback changed significantly depending on the skin pass condition.

A heuristic model selection scheme for representing hot flow data using the hot torsion test results

The problem of "model selection" for expressing a wide range of constitutive behaviour adequately using hot torsion test data was considered here using a heuristic approach. A model library including several nested parametric linear and non-linear models was considered and applied to a set of hot torsion test data for API-X 70 micro-alloyed steel with a range of strain rates and temperatures. A cost function comprising the modelled hot strength data and that of the measured data were utilized in a heuristic model selection scheme to identify the optimum models. It was shown that a non-linear rational model including ten parameters is an optimum model that can accurately express the multiple regimes of hardening and softening for the entire range of the experiment. The parameters for the optimum model were estimated and used for determining variations of hot strength of the samples with deformation.

Post processing of the hot torsion test results using a multi-dimensional modelling approach

A model selection scheme was extended to a multi-dimensional representation of the hot torsion test torque, twist and twist rate data to calculate partial derivatives of the torque data with respect to twist and twist rate. These enabled calculation of the instantaneous strain and strain rate hardening indices in the Fields and Backofen method. The concept of an iso-parametric shape function has been borrowed from the finite element method for adding twist rate as a dependant variable to the torque-twist models identified by the model selection scheme. Expressions to calculate the hardening indices, when employing a rational model of torsion data, were derived and presented. Subsequently, the models were used for post processing the data and determining hot strength behaviour, taking into account variations of strain and strain rate hardening indices during the deformation. To substantiate the technique, the hot flow behaviour of API-X70 micro-alloyed steel was determined using a range of hot torsion test data for the material. The flow stress obtained using the instantaneous hardening indices were compared with that obtained by the orthodox technique. For the investigated cases, the onset of dynamic recrystallization (DRX) predicted by the presented technique deviated considerably from those obtained when the average indices were used.

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.