title: Characterisation, Consolidation and Mechanical Properties of TiAl Alloy Produced Using Titanox Powders

authors: Parmar, Bhupinder

subjects: TiAl alloys

abstract: Characterization of the three different as- received TiAl powders, namely Tax1, Tax2 and Tax3 produced by Titanox development Ltd has been done. Predominate TiAl phase was observed in all the three compositions .The powder particles were very fine with average particle size of 12μm, 5μm and 10μm respectively for Tax1, Tax2 and Tax3.Chemical analysis of the powders showed high oxygen content in all the three compositions of the powders .
Bulk samples were produced from Tax1, Tax2 and Tax3 powders by hot isostatic pressing at 1200  C under a pressure of 200Mpa for two hours .The pressurization gas used for the process was argon. The relative density of Tax1, Tax2 and Tax3 HIPped samples was 96%, 86% and 93%and respectively. The characterization of the HIPped samples showed that the predominate phase was γ-TiAl phase in all the three HIPped samples .A small fractions of Ti3Al and TiAl3 was also observed in tax1 and Tax3 HIPped material. Also some of the dark Al rich phases was Al2O3 phase in Tax1 and Tax3 HIPped samples. High oxygen content of the powder and air leaking in the can during the process of press-seal and welding of the end of the tube of the can prior to HIPping lead to poor consolidation of Tax2 which eventually resulted in high porosity and formation of Ti2O and Al2O3. Half of the Tax2 HIPped sample was canned and heated to 1160 C and was subjected to open die hammer forging with a high strain and a total reduction of height by 66% .The forging produced a pancake shaped sample without breaking of the sample.
Tensile specimens were cut from the Tax1 and Tax3 HIPped sample and one from the Tax2 forged sample using electrical discharge machine (EDM) wirecutting. Tax1 HIPped material showed the average fracture strength of 204MPa, 256MPa and 197MPa at room temperature, 800 C and 900 C respectively., Whereas Tax3 HIPped material showed average fracture strength of 103MPa and 234MPa respectively at room temperature and 800 C respectively. The HIPped and the forged Tax2 sample showed low fracture strength of 91MPa because of the micro-cracks produced during forging.

text: Characterisation, Consolidation and Mechanical Properties of TiAl Alloy Produced Using Titanox Powders Characterization of the three different as- received TiAl powders, namely Tax1, Tax2 and Tax3 produced by Titanox development Ltd has been done. Predominate TiAl phase was observed in all the three compositions .The powder particles were very fine with average particle size of 12μm, 5μm and 10μm respectively for Tax1, Tax2 and Tax3.Chemical analysis of the powders showed high oxygen content in all the three compositions of the powders .
Bulk samples were produced from Tax1, Tax2 and Tax3 powders by hot isostatic pressing at 1200  C under a pressure of 200Mpa for two hours .The pressurization gas used for the process was argon. The relative density of Tax1, Tax2 and Tax3 HIPped samples was 96%, 86% and 93%and respectively. The characterization of the HIPped samples showed that the predominate phase was γ-TiAl phase in all the three HIPped samples .A small fractions of Ti3Al and TiAl3 was also observed in tax1 and Tax3 HIPped material. Also some of the dark Al rich phases was Al2O3 phase in Tax1 and Tax3 HIPped samples. High oxygen content of the powder and air leaking in the can during the process of press-seal and welding of the end of the tube of the can prior to HIPping lead to poor consolidation of Tax2 which eventually resulted in high porosity and formation of Ti2O and Al2O3. Half of the Tax2 HIPped sample was canned and heated to 1160 C and was subjected to open die hammer forging with a high strain and a total reduction of height by 66% .The forging produced a pancake shaped sample without breaking of the sample.
Tensile specimens were cut from the Tax1 and Tax3 HIPped sample and one from the Tax2 forged sample using electrical discharge machine (EDM) wirecutting. Tax1 HIPped material showed the average fracture strength of 204MPa, 256MPa and 197MPa at room temperature, 800 C and 900 C respectively., Whereas Tax3 HIPped material showed average fracture strength of 103MPa and 234MPa respectively at room temperature and 800 C respectively. The HIPped and the forged Tax2 sample showed low fracture strength of 91MPa because of the micro-cracks produced during forging.

year: 2007

title: Editorial: The experience and benefits of game playing

authors: Lorentz, Pascaline

subjects: Social Sciences

abstract: Now that video games have permeated daily life across the globe on computers, consoles and pocket devices, they call for a more comprehensive—and accurate—understanding of their role in society. Psychological research into the impact of games upon players was initiated more than fifteen years ago, with researches devoted to uncovering the alleged negative impact of game playing in response to politically driven moral panics. The focus and dominance of experimental ‘effects’ research has given rise to a need for further research to balance what is sometimes seen as moral crusades associated with causation studies to articulate the more mundane, less contentious existence of games as a significant leisure activity for billions of individuals who repeatedly play them for entertainment and fun.

text: Editorial: The experience and benefits of game playing Now that video games have permeated daily life across the globe on computers, consoles and pocket devices, they call for a more comprehensive—and accurate—understanding of their role in society. Psychological research into the impact of games upon players was initiated more than fifteen years ago, with researches devoted to uncovering the alleged negative impact of game playing in response to politically driven moral panics. The focus and dominance of experimental ‘effects’ research has given rise to a need for further research to balance what is sometimes seen as moral crusades associated with causation studies to articulate the more mundane, less contentious existence of games as a significant leisure activity for billions of individuals who repeatedly play them for entertainment and fun.

year: 2015

title: Microbiological quality of Toroi:  A Māori food delicacy

authors: Dixon, Lorraine Louise

subjects: Maori

abstract: A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

text: Microbiological quality of Toroi:  A Māori food delicacy A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

year: 2007