title: The mechanical behaviour of an ultrafine grained Ti-47Al-2Cr (at%) alloy in tension and compression and at different temperatures

authors: Nadakuduru, Vijay Navaratna

subjects: ultrafine grained

abstract: A bulk ultrafine grained (UFG) Ti-47Al-2Cr (at%) alloy has been produced using a powder metallurgy process that combines high energy mechanical milling (HEMM) of a mixture of Ti, Al and Cr powders to produce a Ti/Al/Cr composite powder and hot isostatic pressing (HIP) of the composite powder compact. The purpose of the present study is to determine the mechanical behaviour of the alloy in tension and compression at room temperature (RT) and elevated temperatures, and also to compare the compression behaviour of the material with its tensile behaviour. It has been found that due to the residual pores, lack of full level interparticle bonding and high oxygen content (0.87wt%) in the consolidated samples, the UFG TiAl based alloy has a very low room temperature tensile fracture strength of 100 MPa and shows no tensile ductility. However these microstructural defects and high oxygen content have much less significant effect on the room temperature compressive mechanical properties, and the alloy shows a high compressive yield strength of  1410 MPa, and some ductility (plastic strain to fracture  4%). At elevated temperatures of 800oC and above, the alloy shows high tensile and compressive ductility as demonstrated by 75% tensile elongation to fracture and no cracking in upset forging with a height reduction of 50% at 900oC. The yield strength of the alloy at 900oC is 55 MPa in tension and  33 MPa in compression, both of which are lower than those of coarse grained TiAl based alloys with similar compositions at 900oC. This is due to a higher creep rate of the UFG alloy caused by the small grains. The good formability of the UFG TiAl based alloy as reflected by the lower critical temperature above which the alloy becomes highly formable indicates that the material can be used as a suitable precursor for secondary thermomechanical processing and super-plastic forming.

text: The mechanical behaviour of an ultrafine grained Ti-47Al-2Cr (at%) alloy in tension and compression and at different temperatures A bulk ultrafine grained (UFG) Ti-47Al-2Cr (at%) alloy has been produced using a powder metallurgy process that combines high energy mechanical milling (HEMM) of a mixture of Ti, Al and Cr powders to produce a Ti/Al/Cr composite powder and hot isostatic pressing (HIP) of the composite powder compact. The purpose of the present study is to determine the mechanical behaviour of the alloy in tension and compression at room temperature (RT) and elevated temperatures, and also to compare the compression behaviour of the material with its tensile behaviour. It has been found that due to the residual pores, lack of full level interparticle bonding and high oxygen content (0.87wt%) in the consolidated samples, the UFG TiAl based alloy has a very low room temperature tensile fracture strength of 100 MPa and shows no tensile ductility. However these microstructural defects and high oxygen content have much less significant effect on the room temperature compressive mechanical properties, and the alloy shows a high compressive yield strength of  1410 MPa, and some ductility (plastic strain to fracture  4%). At elevated temperatures of 800oC and above, the alloy shows high tensile and compressive ductility as demonstrated by 75% tensile elongation to fracture and no cracking in upset forging with a height reduction of 50% at 900oC. The yield strength of the alloy at 900oC is 55 MPa in tension and  33 MPa in compression, both of which are lower than those of coarse grained TiAl based alloys with similar compositions at 900oC. This is due to a higher creep rate of the UFG alloy caused by the small grains. The good formability of the UFG TiAl based alloy as reflected by the lower critical temperature above which the alloy becomes highly formable indicates that the material can be used as a suitable precursor for secondary thermomechanical processing and super-plastic forming.

year: 2011

title: Biocontrol of aquatic weeds

authors: Paynter, Quentin

abstract: Current control methods for aquatic weeds in New Zealand include mechanical control, herbicides and inundative biological control using sterile grass carp as well as habitat manipulation and integrated control. These options have been used to successfully eradicate weeds (both on a local scale and nationally) and are often highly cost-effective. However, a relatively small number of aquatic weed species have become so widespread that the cost of using these techniques against them can be prohibitive. For example, the annual control costs for hornwort in New Zealand are approximately $3.3 million/yr. A new control method with the potential to reduce these management costs is desirable. In this talk I shall discuss the potential for using classical biological control to tackle some of the worst submerged aquatic weeds in New Zealand.

text: Biocontrol of aquatic weeds Current control methods for aquatic weeds in New Zealand include mechanical control, herbicides and inundative biological control using sterile grass carp as well as habitat manipulation and integrated control. These options have been used to successfully eradicate weeds (both on a local scale and nationally) and are often highly cost-effective. However, a relatively small number of aquatic weed species have become so widespread that the cost of using these techniques against them can be prohibitive. For example, the annual control costs for hornwort in New Zealand are approximately $3.3 million/yr. A new control method with the potential to reduce these management costs is desirable. In this talk I shall discuss the potential for using classical biological control to tackle some of the worst submerged aquatic weeds in New Zealand.

year: 2015

title: A critical analysis of Section 27 of the Sentencing Act (2002)

authors: Oakley, Tara Joan

subjects: Section 27

abstract: This thesis analyses the effectiveness of Section 27 of the Sentencing Act (2002) in achieving its primary objective of addressing the high rate of Māori incarceration. This problem largely stems from the destruction of Māori culture through colonisation and is held in place by systemic and institutional racism in the contemporary context. Theoretically, Section 27 provides a mechanism to off-set the societal dislocation and disadvantage Māori have experienced as a result of colonialism, crime control policies and urbanisation.

Analysis of the operational reality of Section 27 focused on the following questions:
•	Is Section 27 being utilised as intended by legislation?
•	What are the underlying rationale and reasons why the Section is utilised by Court officials?
•	What are the underlying rationale and reasons why the Section is not utilised by Court officials?
•	What changes to legislation, policy or institutional practice are required to enhance the use of Section 27?
The research involved qualitative interviews of eight lawyers from two different geographic locations in New Zealand, and four cultural consultants (those employed to write professional Section 27 reports). Their responses were analysed and grouped into three different themes: benefits, barriers, and improvement to legislation and practice.  

Major findings of the research include positive outcomes such as improved community re-engagement for offenders and improved sentencing outcomes. On the other hand, however, there is an inconsistency of use of Section 27, as well as a variable impact when it is used during the sentencing process. This inconsistency appears due to a lack of cultural knowledge and understanding within the court system. Thus, there is a need for cultural education of those working within the court system and for the development of a framework and guidelines.  For this to be imbedded as a consistent practice for use in sentencing decisions it needs to be backed up with adequate government funding and legislative and policy support.

text: A critical analysis of Section 27 of the Sentencing Act (2002) This thesis analyses the effectiveness of Section 27 of the Sentencing Act (2002) in achieving its primary objective of addressing the high rate of Māori incarceration. This problem largely stems from the destruction of Māori culture through colonisation and is held in place by systemic and institutional racism in the contemporary context. Theoretically, Section 27 provides a mechanism to off-set the societal dislocation and disadvantage Māori have experienced as a result of colonialism, crime control policies and urbanisation.

Analysis of the operational reality of Section 27 focused on the following questions:
•	Is Section 27 being utilised as intended by legislation?
•	What are the underlying rationale and reasons why the Section is utilised by Court officials?
•	What are the underlying rationale and reasons why the Section is not utilised by Court officials?
•	What changes to legislation, policy or institutional practice are required to enhance the use of Section 27?
The research involved qualitative interviews of eight lawyers from two different geographic locations in New Zealand, and four cultural consultants (those employed to write professional Section 27 reports). Their responses were analysed and grouped into three different themes: benefits, barriers, and improvement to legislation and practice.  

Major findings of the research include positive outcomes such as improved community re-engagement for offenders and improved sentencing outcomes. On the other hand, however, there is an inconsistency of use of Section 27, as well as a variable impact when it is used during the sentencing process. This inconsistency appears due to a lack of cultural knowledge and understanding within the court system. Thus, there is a need for cultural education of those working within the court system and for the development of a framework and guidelines.  For this to be imbedded as a consistent practice for use in sentencing decisions it needs to be backed up with adequate government funding and legislative and policy support.

year: 2020