title: Study on Low-cost Alternatives for Synthesising Powder Metallurgy Titanium and Titanium Alloys

authors: Raynova, Stiliana (Stella) Rousseva

subjects: titanium

abstract: The aim of this work was to carry out research about cost effective ways for synthesising powder metallurgy Ti and Ti alloys. This was done: using low cost Ti powders produced by the hydrogenation dehydrogenation (HDH) method; using induction heating, instead of the more traditionally used electrically heated vacuum furnace, for sintering and in the thermomechanical processing of powders; using low cost alloying elements such as Fe and stainless steel powders and investigating the possibility of using low amounts of alloying elements. 
The first main stream investigation in this work focussed on a study of induction sintering of Ti and pre-alloyed Ti6Al4V powders. This initial work included the following investigations: the effect of powder compact density on induction heating rates, the levels of porosity and the tensile properties of sintered samples; and the effect of induction sintering process parameters, such as temperature and time on the sintered densities, porosity distribution, microstructure, tensile properties and fracture characteristics of Ti and pre-alloyed Ti6Al4V powders.
The second main study was on the application of induction sintering for consolidating pre-alloyed Ti6Al4V powders by thermomechanical processing via open die forging. The aim was to reduce processing time by eliminating the need for lengthy vacuum sintering and additional reheating required before final processing. The effect of the induction sintering parameters on the deformation behaviour, microstructure, mechanical properties and fracture behaviour were studied. Furthermore, the effect of a recrystallization annealing heat treatment on the tensile properties and microstructure was also analysed.
The third study was focused on the development of low cost powder metallurgy Ti alloys with mechanical properties similar to those of the most commonly used wrought Ti6Al4V alloy. To achieve this aim an approach using Ti HDH powder with a high oxygen content of 0.25wt% was used along with low cost alloying elements such as Fe and stainless steel powders.  The maximum alloying element content was limited to 5% and a blended elemental approach for making the alloys was employed. Induction sintering and vacuum sintering prior to thermomechanical processing by open die forging and extrusion were used for consolidation. The alloy compositions studied were Ti3Al2V, Ti5Fe with two different particle sizes of Fe powder and Ti5SS (addition of 316 stainless steel powder). A blended elemental Ti6Al4V alloy was also studied for comparison. The relationship between microstructure, mechanical properties and fracture behaviour was studied. The effect of recrystallization annealing after forging and extrusion was investigated for some of the alloys on its effect on microstructure and tensile properties. 
The results showed that induction sintering significantly reduces the sintering time. Induction sintering for four to ten minutes produces Ti and Ti alloy with closed porosity structures as well as densities and mechanical properties comparable with those found in vacuum sintered Ti based material.
 The use of induction sintering in direct open die forging of prealloyed Ti6Al4V powders with a high oxygen content of 0.5wt% resulted in material with a solid structure and tensile properties, such as YS and UTS, significantly higher than those given by wrought Ti6Al4V alloy. The ductility was affected by the high oxygen content and was generally lower than that of the wrought material.
Thermomechanical processing of the low cost alloys Ti5Fe, Ti5SS and Ti3Al2V with oxygen contents between 0.33wt% and 0.45wt% resulted in material with an excellent combination of tensile strength and ductility, comparable to the values found in wrought Ti6Al4V alloy. A post forging or extrusion recrystallization annealing heat treatment played a significant role in producing microstructures with fine α+β lamellae, which was a controlling factor for achieving good ductility in Ti alloys with a high oxygen content.

text: Study on Low-cost Alternatives for Synthesising Powder Metallurgy Titanium and Titanium Alloys The aim of this work was to carry out research about cost effective ways for synthesising powder metallurgy Ti and Ti alloys. This was done: using low cost Ti powders produced by the hydrogenation dehydrogenation (HDH) method; using induction heating, instead of the more traditionally used electrically heated vacuum furnace, for sintering and in the thermomechanical processing of powders; using low cost alloying elements such as Fe and stainless steel powders and investigating the possibility of using low amounts of alloying elements. 
The first main stream investigation in this work focussed on a study of induction sintering of Ti and pre-alloyed Ti6Al4V powders. This initial work included the following investigations: the effect of powder compact density on induction heating rates, the levels of porosity and the tensile properties of sintered samples; and the effect of induction sintering process parameters, such as temperature and time on the sintered densities, porosity distribution, microstructure, tensile properties and fracture characteristics of Ti and pre-alloyed Ti6Al4V powders.
The second main study was on the application of induction sintering for consolidating pre-alloyed Ti6Al4V powders by thermomechanical processing via open die forging. The aim was to reduce processing time by eliminating the need for lengthy vacuum sintering and additional reheating required before final processing. The effect of the induction sintering parameters on the deformation behaviour, microstructure, mechanical properties and fracture behaviour were studied. Furthermore, the effect of a recrystallization annealing heat treatment on the tensile properties and microstructure was also analysed.
The third study was focused on the development of low cost powder metallurgy Ti alloys with mechanical properties similar to those of the most commonly used wrought Ti6Al4V alloy. To achieve this aim an approach using Ti HDH powder with a high oxygen content of 0.25wt% was used along with low cost alloying elements such as Fe and stainless steel powders.  The maximum alloying element content was limited to 5% and a blended elemental approach for making the alloys was employed. Induction sintering and vacuum sintering prior to thermomechanical processing by open die forging and extrusion were used for consolidation. The alloy compositions studied were Ti3Al2V, Ti5Fe with two different particle sizes of Fe powder and Ti5SS (addition of 316 stainless steel powder). A blended elemental Ti6Al4V alloy was also studied for comparison. The relationship between microstructure, mechanical properties and fracture behaviour was studied. The effect of recrystallization annealing after forging and extrusion was investigated for some of the alloys on its effect on microstructure and tensile properties. 
The results showed that induction sintering significantly reduces the sintering time. Induction sintering for four to ten minutes produces Ti and Ti alloy with closed porosity structures as well as densities and mechanical properties comparable with those found in vacuum sintered Ti based material.
 The use of induction sintering in direct open die forging of prealloyed Ti6Al4V powders with a high oxygen content of 0.5wt% resulted in material with a solid structure and tensile properties, such as YS and UTS, significantly higher than those given by wrought Ti6Al4V alloy. The ductility was affected by the high oxygen content and was generally lower than that of the wrought material.
Thermomechanical processing of the low cost alloys Ti5Fe, Ti5SS and Ti3Al2V with oxygen contents between 0.33wt% and 0.45wt% resulted in material with an excellent combination of tensile strength and ductility, comparable to the values found in wrought Ti6Al4V alloy. A post forging or extrusion recrystallization annealing heat treatment played a significant role in producing microstructures with fine α+β lamellae, which was a controlling factor for achieving good ductility in Ti alloys with a high oxygen content.

year: 2017

title: Designing Effective Interfaces for Older Users

authors: Hawthorn, Dan

subjects: UI

abstract: The thesis examines the factors that need to be considered in order to undertake successful design of user interfaces for older users. The literature on aging is surveyed for age related changes that are of relevance to interface design. The findings from the literature review are extended and placed in a human context using observational studies of older people and their supporters as these older people attempted to learn about and use computers. These findings are then applied in three case studies of interface design and product development for older users. These case studies are reported and examined in depth. For each case study results are presented on the acceptance of the final product by older people. These results show that, for each case study, the interfaces used led to products that the older people evaluating them rated as unusually suitable to their needs as older users. The relationship between the case studies and the overall research aims is then examined in a discussion of the research methodology. In the case studies there is an evolving approach used in developing the interface designs. This approach includes intensive contribution by older people to the shaping of the interface design. This approach is analyzed and is presented as an approach to designing user interfaces for older people. It was found that a number of non-standard techniques were useful in order to maximize the benefit from the involvement of the older contributors and to ensure their ethical treatment. These techniques and the rationale behind them are described. Finally the interface design approach that emerged has strong links to the approach used by the UTOPIA team based at the university of Dundee. The extent to which the thesis provides support for the UTOPIA approach is discussed.

text: Designing Effective Interfaces for Older Users The thesis examines the factors that need to be considered in order to undertake successful design of user interfaces for older users. The literature on aging is surveyed for age related changes that are of relevance to interface design. The findings from the literature review are extended and placed in a human context using observational studies of older people and their supporters as these older people attempted to learn about and use computers. These findings are then applied in three case studies of interface design and product development for older users. These case studies are reported and examined in depth. For each case study results are presented on the acceptance of the final product by older people. These results show that, for each case study, the interfaces used led to products that the older people evaluating them rated as unusually suitable to their needs as older users. The relationship between the case studies and the overall research aims is then examined in a discussion of the research methodology. In the case studies there is an evolving approach used in developing the interface designs. This approach includes intensive contribution by older people to the shaping of the interface design. This approach is analyzed and is presented as an approach to designing user interfaces for older people. It was found that a number of non-standard techniques were useful in order to maximize the benefit from the involvement of the older contributors and to ensure their ethical treatment. These techniques and the rationale behind them are described. Finally the interface design approach that emerged has strong links to the approach used by the UTOPIA team based at the university of Dundee. The extent to which the thesis provides support for the UTOPIA approach is discussed.

year: 2006

title: Pōwhiri: A framing to strengthen bicultural belonging for refugee children and families in early childhood education

authors: Rameka, Lesley Kay

subjects: bicultural belonging

abstract: A crucial task for refugee families and children who settle in Aotearoa New Zealand is to develop a sense of belonging in that place, time and environment. Belonging is a basic human need. It is a driving force for learning how to be and behave in a new setting and a springboard for participation (Guo & Dalli, 2016; Sumsion & Wong, 2011). As a concept, ‘belonging’ is acknowledged to be multifaceted, culturally-determined, and complex. This article focuses on phase two of the Refugee families in early childhood education: Constructing pathways to belonging research project, which involved trialling and evaluating, with early childhood services, the pōwhiri (Māori ceremony of welcome) framing, developed in phase one of the research. The framing offers concepts to enable understanding of the phases and processes for refugee and immigrant families to develop a sense of bicultural belonging in Aotearoa New Zealand. Pōwhiri is the traditional Māori ceremony of welcome or ritual of encounter, performed across Aotearoa New Zealand, by the host people to welcome visitors to their region. Pōwhiri is explained in this article as a physical process following standard phases, with each phase including metaphorical understandings.

text: Pōwhiri: A framing to strengthen bicultural belonging for refugee children and families in early childhood education A crucial task for refugee families and children who settle in Aotearoa New Zealand is to develop a sense of belonging in that place, time and environment. Belonging is a basic human need. It is a driving force for learning how to be and behave in a new setting and a springboard for participation (Guo & Dalli, 2016; Sumsion & Wong, 2011). As a concept, ‘belonging’ is acknowledged to be multifaceted, culturally-determined, and complex. This article focuses on phase two of the Refugee families in early childhood education: Constructing pathways to belonging research project, which involved trialling and evaluating, with early childhood services, the pōwhiri (Māori ceremony of welcome) framing, developed in phase one of the research. The framing offers concepts to enable understanding of the phases and processes for refugee and immigrant families to develop a sense of bicultural belonging in Aotearoa New Zealand. Pōwhiri is the traditional Māori ceremony of welcome or ritual of encounter, performed across Aotearoa New Zealand, by the host people to welcome visitors to their region. Pōwhiri is explained in this article as a physical process following standard phases, with each phase including metaphorical understandings.

year: 2022