title: Tensile properties of Ti-6Al-4V discs produced by open die powder compact forging of pre-alloyed HDH powders

authors: Raynova, Stiliana (Stella) Rousseva

subjects: Forging

abstract: Open die powder compact forging was employed for consolidation of Ti-6Al-4V(wt.%) powders which were produced by a hydride-dehydride (HDH) process. The powders were initially warm-compacted into cylindrical shapes. Induction heating was used for preheating the compacts prior to forging into plates. The effect of the forging parameters such as temperature and pre-sintering time on the microstructure and tensile properties of the forged plates were studied. Porosity and the alpha-beta phase distribution were investigated to enable a better understanding of their effect on the fracture behaviour of the tensile tested specimens. The fracture surfaces of the broken tensile specimens were analysed using Scanning Electron Microscopy (SEM) to find the correlation between microstructure, residual porosity and fracture behaviour. A combination of high ultimate tensile strength of over 1200MPa and a good ductility reflected by an elongation to fracture of around 10% was achieved in some of the forged discs.

text: Tensile properties of Ti-6Al-4V discs produced by open die powder compact forging of pre-alloyed HDH powders Open die powder compact forging was employed for consolidation of Ti-6Al-4V(wt.%) powders which were produced by a hydride-dehydride (HDH) process. The powders were initially warm-compacted into cylindrical shapes. Induction heating was used for preheating the compacts prior to forging into plates. The effect of the forging parameters such as temperature and pre-sintering time on the microstructure and tensile properties of the forged plates were studied. Porosity and the alpha-beta phase distribution were investigated to enable a better understanding of their effect on the fracture behaviour of the tensile tested specimens. The fracture surfaces of the broken tensile specimens were analysed using Scanning Electron Microscopy (SEM) to find the correlation between microstructure, residual porosity and fracture behaviour. A combination of high ultimate tensile strength of over 1200MPa and a good ductility reflected by an elongation to fracture of around 10% was achieved in some of the forged discs.

year: 2012

title: Liberalising Event B without changing it

authors: Reeves, Steve

subjects: process refinement

abstract: We transfer a process algebraic notion of refinement to the B method by using the well-known bridge between the relational semantics underlying the B machines and the labelled transition system semantics of processes. Thus we define delta refinement on Event B systems. We then apply this new refinement to a problem from the literature that previously could only be solved by retrenchment.

text: Liberalising Event B without changing it We transfer a process algebraic notion of refinement to the B method by using the well-known bridge between the relational semantics underlying the B machines and the labelled transition system semantics of processes. Thus we define delta refinement on Event B systems. We then apply this new refinement to a problem from the literature that previously could only be solved by retrenchment.

year: 2006-07-01

title: Disrupted spaces: Racism and the lived experience of Maori identity formation

authors: Te Hiwi, Erika

subjects: Maori

abstract: In 2004, when Don Brash –then leader of the National Party, hit the headlines with his controversial ‘Orewa’ speech, so-called ‘mainstream’ New Zealanders, felt that at last they had their hero. Brash articulated what this group felt was the source of trouble in contemporary Aotearoa society – brown privilege. Letters to the editor and talkback lines ran hot with many applauding Brash’s calls for an end to the treaty gravy train and ‘race-based’ funding in health; anecdotes abounded of Māori students up and down the country getting a ‘free-ride’ through education and taking prized positions in training programmes from better qualified Pākehā. It was, according to the writers and callers, an oppressive Apartheid-style system favouring Māori that had to end.

text: Disrupted spaces: Racism and the lived experience of Maori identity formation In 2004, when Don Brash –then leader of the National Party, hit the headlines with his controversial ‘Orewa’ speech, so-called ‘mainstream’ New Zealanders, felt that at last they had their hero. Brash articulated what this group felt was the source of trouble in contemporary Aotearoa society – brown privilege. Letters to the editor and talkback lines ran hot with many applauding Brash’s calls for an end to the treaty gravy train and ‘race-based’ funding in health; anecdotes abounded of Māori students up and down the country getting a ‘free-ride’ through education and taking prized positions in training programmes from better qualified Pākehā. It was, according to the writers and callers, an oppressive Apartheid-style system favouring Māori that had to end.

year: 2008