title: Tensile properties and fracture behaviour of an ultrafine grained Ti–47Al–2Cr (at.%) alloy at room and elevated temperatures

authors: Nadakuduru, Vijay Navaratna

subjects: brittle to ductile transition temperature

abstract: An ultrafine grained (UFG) Ti–47Al–2Cr (at.%) alloy has been synthesized using a combination of high energy mechanical milling and hot isostatic pressing (HIP) of a Ti/Al/Cr composite powder compact. The material produced has been tensile tested at room temperature, 700 and 800 °C, respectively, and the microstructure of the as-HIPed material and the microstructure and fracture surfaces of the tensile tested specimens have been examined using X-ray diffractometry, optical microscopy, scanning electron microscopy and transmission electron microscopy. The alloy shows no ductility during tensile testing at room temperature and 700 °C, respectively, but very high ductility (elongation to fracture 70–100%) when tensile tested 800 °C, indicating that its brittle to ductile transition temperature (BDTT) falls within the temperature range of 700–800 °C. The retaining of ultrafine fine equiaxed grain morphology after the large amount of plastic deformation of the specimens tensile tested at 800 °C and the clear morphology of individual grains in the fractured surface indicate that grain boundary sliding is the predominant deformation mechanism of plastic deformation of the UFG TiAl based alloy at 800 °C. Cavitation occurs at locations fairly uniformly distributed throughout the gauge length sections of the specimens tensile tested at 800 °C, again supporting the postulation that grain boundary sliding is the dominant mechanism of the plastic deformation of the UFG TiAl alloys at temperatures above their BDTT. The high ductility of the UFG alloy at 800 °C and its fairly low BDTT indicates that the material a highly favourable precursor for secondary thermomechanical processing.

text: Tensile properties and fracture behaviour of an ultrafine grained Ti–47Al–2Cr (at.%) alloy at room and elevated temperatures An ultrafine grained (UFG) Ti–47Al–2Cr (at.%) alloy has been synthesized using a combination of high energy mechanical milling and hot isostatic pressing (HIP) of a Ti/Al/Cr composite powder compact. The material produced has been tensile tested at room temperature, 700 and 800 °C, respectively, and the microstructure of the as-HIPed material and the microstructure and fracture surfaces of the tensile tested specimens have been examined using X-ray diffractometry, optical microscopy, scanning electron microscopy and transmission electron microscopy. The alloy shows no ductility during tensile testing at room temperature and 700 °C, respectively, but very high ductility (elongation to fracture 70–100%) when tensile tested 800 °C, indicating that its brittle to ductile transition temperature (BDTT) falls within the temperature range of 700–800 °C. The retaining of ultrafine fine equiaxed grain morphology after the large amount of plastic deformation of the specimens tensile tested at 800 °C and the clear morphology of individual grains in the fractured surface indicate that grain boundary sliding is the predominant deformation mechanism of plastic deformation of the UFG TiAl based alloy at 800 °C. Cavitation occurs at locations fairly uniformly distributed throughout the gauge length sections of the specimens tensile tested at 800 °C, again supporting the postulation that grain boundary sliding is the dominant mechanism of the plastic deformation of the UFG TiAl alloys at temperatures above their BDTT. The high ductility of the UFG alloy at 800 °C and its fairly low BDTT indicates that the material a highly favourable precursor for secondary thermomechanical processing.

year: 2012

title: Assessment of injury to New Zealand native fish by boat electrofishing

authors: de Villiers, Joshua

subjects: Electrofishing

abstract: This study investigated the survival, incidence and severity of injuries and physiological reactions to stress caused by boat electrofishing in comparison with standard netting techniques in three New Zealand native fish species. Shortfin eel (Anguilla australis), grey mullet (Mugil cephalus) and common smelt (Retropinna retropinna) were captured from the Waikato River and its surrounding lakes with standardised boat electrofishing techniques (60-Hz pulsed direct current, 45-60% of range with the 0-500-V peak voltage machine setting, 3-4 Amps root mean square output). Fish were captured in water of 133-154 μScm─1 ambient conductivity at 18-21oC. Capture techniques used for comparison were fyke netting for eels, gill netting for grey mullet and beach seine netting for smelt.
Survival was assessed in eels that held for 30 days after capture and smelt that were held for 30 min after capture. Several different methods were used to assess the incidence and severity of injuries. External examinations were used to assess branding and abrasions, and internal injuries were assessed by radiographic imaging and bilateral filleting to reveal haemorrhaging and spinal damage. Finally, physiological stress was determined by an analysis of haematocrit and haemoglobin concentration and an analysis of blood plasma ions (sodium, potassium, magnesium and calcium).
Survival over 30 days of shortfin eels captured by electrofishing (92% for Lake Areare eels and 96% for Lake Rotongaro eels) was similar to that for fyke netting (92% for Lake Areare and 88% for Lake Rotongaro). Two eels appeared to have died from fungal infections as no haemorrhaging or spinal injuries were apparent among the mortalities. External examinations revealed that no abrasions or branding occurred in eels captured by electrofishing; however, abrasions occurred in eels captured by fyke netting (24% for Lake Areare eels and 16% for Lake Rotongaro eels).
Rates of internal haemorrhaging immediately after electrofishing were inconsistent (0% in Lake Areare and 28% in Lake Rotongaro); in Lake Rotongaro, this was significantly greater than those captured by fyke netting, in which only 8% had haemorrhages. No haemorrhaging was observed in eels after 30 days from Lake Areare. Haemorrhages from electrofishing in our study appeared to heal within the 30-day holding period, as the incidence of haemorrhaging in Rotongaro eels reduced from 28% at capture to only 4% after 30 days in captivity. Rates of spinal injury in eels captured by electrofishing was also variable (12% in Lake Areare eels and 8% in Lake Rotongaro eels), compared to the rate of spinal injury in eels captured by fyke netting (0% in Lake Areare eels and 4% in Lake Rotongaro eels). The upper rate of haemorrhaging that we found for electrofishing in shortfin eels (28%) was similar to injury rates for electrofished American eels (25%), but our rates of spinal damage (8-12%) were much lower than for American eels (60%).
In grey mullet, there was no significant difference (P > 0.101) in the occurrence of haemorrhages or spinal injuries between the two capture methods. However, physiological stress from electrofishing caused a significantly (t = 2.37, P = 0.02) reduced sodium ion concentration (139.38 ± 13.24 mM) compared to that of gill netting (149.06 ± 15.58 mM). Electrofishing also caused a significantly (t = 4.61, P < 0.001) lower concentration of haemoglobin (86.55 ± 9.21 g L-1) compared to that of grey mullet captured by gill netting (108.81 ± 23.86 g L-1). However, there were no significant differences between capture methods for the other blood plasma constituents tested (haematocrit and the blood plasma ions sodium, potassium, magnesium and calcium).
Survival was high in smelt captured by both electrofishing (94.8%, n = 1217) and by seine netting (92.9%, n = 1271), with no statistically significant difference between the two fishing methods (t = −1.021, P = 0.320). In a subsample of smelt analysed for injuries (n = 40 for each method), external injuries were observed in 15% (n = 6) of smelt captured by electrofishing and in 20% (n = 8) of smelt captured by seine netting. No haemorrhages were detected in smelt for either of the capture methods and there was no significant difference (G = 0.215, P = 0.642) in the rate of spinal injuries in smelt captured by electrofishing (10%, n = 4) or by seine netting (5%, n = 2).
These results suggest that boat electrofishing as practiced in New Zealand is in the long term generally no more harmful to shortfin eels, grey mullet, and common smelt than other comparable capture sampling techniques. Exceptions to this
conclusion were increased haemorrhaging in electrofished shortfin eels, from which they recovered within 30 days, and reduced sodium and haemoglobin concentrations in electrofished grey mullet, which are signs of physiological stress. All fishing methods examined caused some level of injury, stress, or mortality in the three species studied. Netting techniques (fyke net, gill netting, and seine netting) that are commonly used will also cause harm and these techniques are currently used far more widely than boat electrofishing.

text: Assessment of injury to New Zealand native fish by boat electrofishing This study investigated the survival, incidence and severity of injuries and physiological reactions to stress caused by boat electrofishing in comparison with standard netting techniques in three New Zealand native fish species. Shortfin eel (Anguilla australis), grey mullet (Mugil cephalus) and common smelt (Retropinna retropinna) were captured from the Waikato River and its surrounding lakes with standardised boat electrofishing techniques (60-Hz pulsed direct current, 45-60% of range with the 0-500-V peak voltage machine setting, 3-4 Amps root mean square output). Fish were captured in water of 133-154 μScm─1 ambient conductivity at 18-21oC. Capture techniques used for comparison were fyke netting for eels, gill netting for grey mullet and beach seine netting for smelt.
Survival was assessed in eels that held for 30 days after capture and smelt that were held for 30 min after capture. Several different methods were used to assess the incidence and severity of injuries. External examinations were used to assess branding and abrasions, and internal injuries were assessed by radiographic imaging and bilateral filleting to reveal haemorrhaging and spinal damage. Finally, physiological stress was determined by an analysis of haematocrit and haemoglobin concentration and an analysis of blood plasma ions (sodium, potassium, magnesium and calcium).
Survival over 30 days of shortfin eels captured by electrofishing (92% for Lake Areare eels and 96% for Lake Rotongaro eels) was similar to that for fyke netting (92% for Lake Areare and 88% for Lake Rotongaro). Two eels appeared to have died from fungal infections as no haemorrhaging or spinal injuries were apparent among the mortalities. External examinations revealed that no abrasions or branding occurred in eels captured by electrofishing; however, abrasions occurred in eels captured by fyke netting (24% for Lake Areare eels and 16% for Lake Rotongaro eels).
Rates of internal haemorrhaging immediately after electrofishing were inconsistent (0% in Lake Areare and 28% in Lake Rotongaro); in Lake Rotongaro, this was significantly greater than those captured by fyke netting, in which only 8% had haemorrhages. No haemorrhaging was observed in eels after 30 days from Lake Areare. Haemorrhages from electrofishing in our study appeared to heal within the 30-day holding period, as the incidence of haemorrhaging in Rotongaro eels reduced from 28% at capture to only 4% after 30 days in captivity. Rates of spinal injury in eels captured by electrofishing was also variable (12% in Lake Areare eels and 8% in Lake Rotongaro eels), compared to the rate of spinal injury in eels captured by fyke netting (0% in Lake Areare eels and 4% in Lake Rotongaro eels). The upper rate of haemorrhaging that we found for electrofishing in shortfin eels (28%) was similar to injury rates for electrofished American eels (25%), but our rates of spinal damage (8-12%) were much lower than for American eels (60%).
In grey mullet, there was no significant difference (P > 0.101) in the occurrence of haemorrhages or spinal injuries between the two capture methods. However, physiological stress from electrofishing caused a significantly (t = 2.37, P = 0.02) reduced sodium ion concentration (139.38 ± 13.24 mM) compared to that of gill netting (149.06 ± 15.58 mM). Electrofishing also caused a significantly (t = 4.61, P < 0.001) lower concentration of haemoglobin (86.55 ± 9.21 g L-1) compared to that of grey mullet captured by gill netting (108.81 ± 23.86 g L-1). However, there were no significant differences between capture methods for the other blood plasma constituents tested (haematocrit and the blood plasma ions sodium, potassium, magnesium and calcium).
Survival was high in smelt captured by both electrofishing (94.8%, n = 1217) and by seine netting (92.9%, n = 1271), with no statistically significant difference between the two fishing methods (t = −1.021, P = 0.320). In a subsample of smelt analysed for injuries (n = 40 for each method), external injuries were observed in 15% (n = 6) of smelt captured by electrofishing and in 20% (n = 8) of smelt captured by seine netting. No haemorrhages were detected in smelt for either of the capture methods and there was no significant difference (G = 0.215, P = 0.642) in the rate of spinal injuries in smelt captured by electrofishing (10%, n = 4) or by seine netting (5%, n = 2).
These results suggest that boat electrofishing as practiced in New Zealand is in the long term generally no more harmful to shortfin eels, grey mullet, and common smelt than other comparable capture sampling techniques. Exceptions to this
conclusion were increased haemorrhaging in electrofished shortfin eels, from which they recovered within 30 days, and reduced sodium and haemoglobin concentrations in electrofished grey mullet, which are signs of physiological stress. All fishing methods examined caused some level of injury, stress, or mortality in the three species studied. Netting techniques (fyke net, gill netting, and seine netting) that are commonly used will also cause harm and these techniques are currently used far more widely than boat electrofishing.

year: 2013

title: A criterion referenced analysis and evaluation of the processes involved in formulating a Māori language regeneration strategy for Whakamārama marae

authors: Lewis, Roger Brian

subjects: critical success factors

abstract: The quality of the processes involved in language regeneration strategy formation is critical to the creation of an effective language regeneration strategy and this, in turn, is critical to the achievement of successful language regeneration outcomes. The overall aim of this research project was to evaluate, using a range of effectiveness criteria, the processes involved in the creation of a marae-based te reo Māori regeneration strategy in the hope that others involved in similar projects in the future would benefit and in the hope that the Whakamārama whānau will themselves derive benefit from it in reviewing what has already been achieved. In Chapter 1, the background to the research project and its rationale are outlined
and the research questions and research methods are introduced. Chapter 2 provides a critical review of selected literature in the area of strategic planning aspects of language regeneration and relevant aspects of mātauranga Māori. Using an ethnographic approach, the processes and immediate outcomes (in terms of a
survey report and a regeneration plan for Whakamārama marae) of the language regeneration project are outlined in Chapter 3. In Chapter 4, effectiveness criteria are derived on the basis of the literature review in Chapter 2. These include criteria relating to leadership, participation, Kaupapa Māori values, environmental
analysis and outcomes. The criteria are then applied to the analysis and evaluation of the processes and outcomes outlined in Chapter 3 in order to identify their strengths and weaknesses. The overall conclusion is that Whakamārama's
language regeneration activities to date can be regarded as successful in many ways, including the fact that they have resulted in the production of high quality documentation that is widely appreciated by the whānau in the form of a maraebased language survey and a marae-based te reo Māori regeneration plan. Working voluntarily and often under difficult circumstances, core group members demonstrated that they possessed the essential characteristics of commitment,
motivation and determination, in addition to the willingness and ability to use existing skills and knowledge effectively and to develop further skills and knowledge as the project proceeded. Perhaps most important, they developed a caring and effective working culture. However, the weaknesses of the project included a lack of preparation and planning prior to the commencement of the project which resulted in a build up of work at a number of stages. This, in turn, lead to delays in producing outcomes and some loss of momentum. It also led, indirectly, to the views of two or three members of the core group being overrepresented in the reo plan goals. The information and analysis provided here
have relevance to any language community involved in micro-level language regeneration activities of a similar type. It is hoped therefore that this thesis may help others to not only avoid the problems experienced by the Whakamārama whānau but also to benefit from their successes.

text: A criterion referenced analysis and evaluation of the processes involved in formulating a Māori language regeneration strategy for Whakamārama marae The quality of the processes involved in language regeneration strategy formation is critical to the creation of an effective language regeneration strategy and this, in turn, is critical to the achievement of successful language regeneration outcomes. The overall aim of this research project was to evaluate, using a range of effectiveness criteria, the processes involved in the creation of a marae-based te reo Māori regeneration strategy in the hope that others involved in similar projects in the future would benefit and in the hope that the Whakamārama whānau will themselves derive benefit from it in reviewing what has already been achieved. In Chapter 1, the background to the research project and its rationale are outlined
and the research questions and research methods are introduced. Chapter 2 provides a critical review of selected literature in the area of strategic planning aspects of language regeneration and relevant aspects of mātauranga Māori. Using an ethnographic approach, the processes and immediate outcomes (in terms of a
survey report and a regeneration plan for Whakamārama marae) of the language regeneration project are outlined in Chapter 3. In Chapter 4, effectiveness criteria are derived on the basis of the literature review in Chapter 2. These include criteria relating to leadership, participation, Kaupapa Māori values, environmental
analysis and outcomes. The criteria are then applied to the analysis and evaluation of the processes and outcomes outlined in Chapter 3 in order to identify their strengths and weaknesses. The overall conclusion is that Whakamārama's
language regeneration activities to date can be regarded as successful in many ways, including the fact that they have resulted in the production of high quality documentation that is widely appreciated by the whānau in the form of a maraebased language survey and a marae-based te reo Māori regeneration plan. Working voluntarily and often under difficult circumstances, core group members demonstrated that they possessed the essential characteristics of commitment,
motivation and determination, in addition to the willingness and ability to use existing skills and knowledge effectively and to develop further skills and knowledge as the project proceeded. Perhaps most important, they developed a caring and effective working culture. However, the weaknesses of the project included a lack of preparation and planning prior to the commencement of the project which resulted in a build up of work at a number of stages. This, in turn, lead to delays in producing outcomes and some loss of momentum. It also led, indirectly, to the views of two or three members of the core group being overrepresented in the reo plan goals. The information and analysis provided here
have relevance to any language community involved in micro-level language regeneration activities of a similar type. It is hoped therefore that this thesis may help others to not only avoid the problems experienced by the Whakamārama whānau but also to benefit from their successes.

year: 2007