title: The Formulation of Titanium - based Metal Feedstocks and the Fabrication of Parts using the Powder Injection Moulding Process

authors: Ewart, Paul Douglas

subjects: Binder

abstract: Development of a profitable titanium industry for New Zealand will not come about without innovative technologies. Plastic injection moulding has long held a place in NZ manufacturing to produce large quantities of complex parts and holds the key to such innovation.
Titanium metal parts were fabricated by injection moulding titanium based metal powder feedstock followed by a debinding process and subsequent sintering. The fabrication process in its entirety was investigated in four distinct steps. Feedstock formulation involved combining the metal powders with various carrier components. Injection moulding enabled the shaping of the feedstock into geometries approximating the final part. Debinding being the process whereby the carrier/binder system is removed from the part to create a powder compact retaining the required geometry. Sintering being the final step where the metal powders are consolidated into a fully dense metal part of net shape.
The feedstock binder consisted of water soluble polyethylene glycol that reduced feedstock viscosity, improved particle wetting, aided greenpart shape retention and eliminated toxic solvents in debinding. Carnauba wax and bees wax aided dispersion, lubricated particles, were safe to handle and better for the environment (than petroleum waxes). Their low melt temperatures aided removal during thermal debinding and supported residue elimination.
By optimising the ratio of water soluble, wax and polyolefin binder components (3: 2: 1 respectively) for melt flow and pellet formation, greenparts defect free with uniform particle distribution were made. The optimal binder system proved suitable for titanium alloy and irregular shape pure titanium powders (hydride-de-hydride). Increasing powder loading (wP = (0.60 to 0.65)) had no appreciable effect on viscosity while enabling feedstock with good uniformity and pellet formation. Dimensional change was not affected by uniformity of the feedstock however molecular weight, volume and dispersion of binder components affected interparticular distances. Low processing temperatures reduced disruption to part geometry, benefitted particle bonding and helped retain handling strength.
The use of low temperatures for thermal debinding (t = 250 °C) enabled removal of the binder below the temperatures that facilitate interstitial diffusion and oxide/carbide formation, although part thickness, mass and overall volume effected the processing time. A strong correlation was seen between handling strength of the greenparts and defects, such as non-uniform density distribution and cracking after sintering.
Sintering was essential to produce the final part and showed that a binder free brownpart was not the only criteria for eliminating impurities. The furnace atmosphere must remain free from contamination to eliminate transfer back to the parts. This was addressed using an argon sweep gas, however, the design and efficacy of the system was considered inadequate. Decomposition products need to be removed quickly from the furnace as they evolve before impurities from the sweep gas diffuse back into the parts during the extended duration at sinter temperatures (t = 1300 °C).
The combination of an optimised titanium feedstock and the use of a low temperature thermal debinding technique produced a consolidated MIM part of relatively large dimensions. The parts were seen to have uniform microstructure throughout the cross-section with density comparable to that of MIM standards. In difference to the literature, a high powder loading (φp = 0.65) of HDH powders was used and shown to be readily mouldable. The higher powder loading also eliminate separation defects and shape distortions evident using lower amounts of powder.

text: The Formulation of Titanium - based Metal Feedstocks and the Fabrication of Parts using the Powder Injection Moulding Process Development of a profitable titanium industry for New Zealand will not come about without innovative technologies. Plastic injection moulding has long held a place in NZ manufacturing to produce large quantities of complex parts and holds the key to such innovation.
Titanium metal parts were fabricated by injection moulding titanium based metal powder feedstock followed by a debinding process and subsequent sintering. The fabrication process in its entirety was investigated in four distinct steps. Feedstock formulation involved combining the metal powders with various carrier components. Injection moulding enabled the shaping of the feedstock into geometries approximating the final part. Debinding being the process whereby the carrier/binder system is removed from the part to create a powder compact retaining the required geometry. Sintering being the final step where the metal powders are consolidated into a fully dense metal part of net shape.
The feedstock binder consisted of water soluble polyethylene glycol that reduced feedstock viscosity, improved particle wetting, aided greenpart shape retention and eliminated toxic solvents in debinding. Carnauba wax and bees wax aided dispersion, lubricated particles, were safe to handle and better for the environment (than petroleum waxes). Their low melt temperatures aided removal during thermal debinding and supported residue elimination.
By optimising the ratio of water soluble, wax and polyolefin binder components (3: 2: 1 respectively) for melt flow and pellet formation, greenparts defect free with uniform particle distribution were made. The optimal binder system proved suitable for titanium alloy and irregular shape pure titanium powders (hydride-de-hydride). Increasing powder loading (wP = (0.60 to 0.65)) had no appreciable effect on viscosity while enabling feedstock with good uniformity and pellet formation. Dimensional change was not affected by uniformity of the feedstock however molecular weight, volume and dispersion of binder components affected interparticular distances. Low processing temperatures reduced disruption to part geometry, benefitted particle bonding and helped retain handling strength.
The use of low temperatures for thermal debinding (t = 250 °C) enabled removal of the binder below the temperatures that facilitate interstitial diffusion and oxide/carbide formation, although part thickness, mass and overall volume effected the processing time. A strong correlation was seen between handling strength of the greenparts and defects, such as non-uniform density distribution and cracking after sintering.
Sintering was essential to produce the final part and showed that a binder free brownpart was not the only criteria for eliminating impurities. The furnace atmosphere must remain free from contamination to eliminate transfer back to the parts. This was addressed using an argon sweep gas, however, the design and efficacy of the system was considered inadequate. Decomposition products need to be removed quickly from the furnace as they evolve before impurities from the sweep gas diffuse back into the parts during the extended duration at sinter temperatures (t = 1300 °C).
The combination of an optimised titanium feedstock and the use of a low temperature thermal debinding technique produced a consolidated MIM part of relatively large dimensions. The parts were seen to have uniform microstructure throughout the cross-section with density comparable to that of MIM standards. In difference to the literature, a high powder loading (φp = 0.65) of HDH powders was used and shown to be readily mouldable. The higher powder loading also eliminate separation defects and shape distortions evident using lower amounts of powder.

year: 2015

title: Netball in the lives of New Zealand Women: An Intergenerational Study

authors: Marfell, Amy Elizabeth

subjects: netball

abstract: This thesis explores the netball experiences of a selection of New Zealand women whom have participated or continue to participate in netball during four distinct historical periods. Adopting an interdisciplinary approach, it sheds light on the broader socio-cultural and political changes that have influenced and shaped women’s experiences of netball throughout history. Drawing upon data gathered from primary and secondary sources and four focus groups, I examine the lived experiences of women who played netball during the 1940’s, 1970’s, 1990’s and the early 21st century. In so doing I reveal how broader shifts in gender relations have impacted women’s netball experiences, focusing particularly on their initial involvement, participation at recreational and competitive levels, and ultimate withdrawal. Moreover, an intergenerational discussion of these women’s experiences reveals some of the differences evident between the experiences of women during these four historical junctures. Exploring women’s netball experiences in relation to broader social change, time and context both within and across generations, this thesis provides unique insights into the changing nature and dynamics of netball in New Zealand, shifting social constructions of femininity and women’s sporting identities, as well as women’s unique and diverse experiences and understandings of their participation.

text: Netball in the lives of New Zealand Women: An Intergenerational Study This thesis explores the netball experiences of a selection of New Zealand women whom have participated or continue to participate in netball during four distinct historical periods. Adopting an interdisciplinary approach, it sheds light on the broader socio-cultural and political changes that have influenced and shaped women’s experiences of netball throughout history. Drawing upon data gathered from primary and secondary sources and four focus groups, I examine the lived experiences of women who played netball during the 1940’s, 1970’s, 1990’s and the early 21st century. In so doing I reveal how broader shifts in gender relations have impacted women’s netball experiences, focusing particularly on their initial involvement, participation at recreational and competitive levels, and ultimate withdrawal. Moreover, an intergenerational discussion of these women’s experiences reveals some of the differences evident between the experiences of women during these four historical junctures. Exploring women’s netball experiences in relation to broader social change, time and context both within and across generations, this thesis provides unique insights into the changing nature and dynamics of netball in New Zealand, shifting social constructions of femininity and women’s sporting identities, as well as women’s unique and diverse experiences and understandings of their participation.

year: 2011

title: How learning stories shape understandings of children’s learning identities in one community of practice: A narrative inquiry

authors: Sands, Lorraine May

subjects: Narrative inquiry

abstract: Mā te mahi, ka mōhio; mā te mōhio, ka mārama; mā te mārama, ka mātau; mā te mātau, ka ora.
From hard work comes knowledge; from that knowledge comes understanding; from that understanding comes strength; from that strength comes wellbeing and life.
This thesis is a listening, dialogic investigation into ways the community of learners at Greerton Early Learning Centre considers learning stories have affected their children’s learning identities—that is, how they view themselves as learners. Aotearoa New Zealand’s early childhood curriculum, Te Whāriki, focuses on responsive, reciprocal relationships wrapped around the uniqueness and mana of each child. Learning stories—a research-based sociocultural narrative assessment approach—have been used in Aotearoa New Zealand early learning settings for over two decades to capture children’s learning while honouring the intent of Te Whāriki to nurture children’s languages, cultures, and identities. In the current climate of privatisation and neoliberalism, however, the value of learning stories is increasingly contested. This study refutes such discourses and instead navigates the value of multiple ways of knowing, meaningfully embedded in the lived experiences of children in relational communities.

This study was embedded in a narrative inquiry paradigm that sees reality as a socially mediated construction contained within stories that are told and retold across times, social contexts, and places. The study aimed to understand and document how storying children’s lived experience makes a meaningful difference to ways children view themselves as learners. Six children, their families, and their teachers were invited to reengage with selected learning stories from the children’s learning portfolios and then to rethink and retell how these learning stories contributed to their views of children’s learning identities.

The study found that learning stories have powerful effects on the ways children see themselves and on the ways those around them see the children as learners. It was clear from the data that children’s learning identities are embedded in the complex social and cultural contexts that surround them. The teachers’ long-term whanaungatanga relationships with mokopuna and whānau enabled kaiako to write learning stories that connected meaningfully with children’s wider historical, social, and cultural contexts. Insights into children’s learning from the learning stories were actively taken up by the parents and shaped the ways they saw and interacted with their children as learners. Likewise, teachers listened to stories shared from home (whether in a written learning story form or simply in the course of conversations), and these contributed to the teachers’ understandings of the children as agentic learners within sociocultural contexts. The physical folders of learning stories offered children powerful ways to maintain connections and a sense of pride in their learning achievements, linked to the people and places that surrounded those achievements.

Learning stories also enabled children to review their learning growth over time, including times when they had set goals, been supported in pursuing those goals by those around them, and had their achievements and dispositions honoured through documentation as a learning story. The process of robust engagement with crafting and reviewing their own and their colleagues’ learning stories played an important role in teachers’ ongoing professional learning. Finally, it was clear that across the whole community of practice—spanning mokopuna, whānau, and kaiako—learning stories played an important role in developing and reinforcing a shared language of learning as well as a shared understanding of the importance of children’s dispositions and working theories as the most highly valued forms of learning.

Although centred in one community, this research stands on the shoulders of many and may have resonance and implications for those in broader contexts. At a time when the usefulness and appropriateness of learning stories are increasingly contested, this study provides an important demonstration of the power of thoughtfully written learning stories and the alignment of this assessment approach with the vision and values of Te Whāriki. Further, with limited past research looking at the intersection of learning stories and children’s learning identities, this study’s rich account of this interaction in one community of practice provides a valuable contribution to the literature.

text: How learning stories shape understandings of children’s learning identities in one community of practice: A narrative inquiry Mā te mahi, ka mōhio; mā te mōhio, ka mārama; mā te mārama, ka mātau; mā te mātau, ka ora.
From hard work comes knowledge; from that knowledge comes understanding; from that understanding comes strength; from that strength comes wellbeing and life.
This thesis is a listening, dialogic investigation into ways the community of learners at Greerton Early Learning Centre considers learning stories have affected their children’s learning identities—that is, how they view themselves as learners. Aotearoa New Zealand’s early childhood curriculum, Te Whāriki, focuses on responsive, reciprocal relationships wrapped around the uniqueness and mana of each child. Learning stories—a research-based sociocultural narrative assessment approach—have been used in Aotearoa New Zealand early learning settings for over two decades to capture children’s learning while honouring the intent of Te Whāriki to nurture children’s languages, cultures, and identities. In the current climate of privatisation and neoliberalism, however, the value of learning stories is increasingly contested. This study refutes such discourses and instead navigates the value of multiple ways of knowing, meaningfully embedded in the lived experiences of children in relational communities.

This study was embedded in a narrative inquiry paradigm that sees reality as a socially mediated construction contained within stories that are told and retold across times, social contexts, and places. The study aimed to understand and document how storying children’s lived experience makes a meaningful difference to ways children view themselves as learners. Six children, their families, and their teachers were invited to reengage with selected learning stories from the children’s learning portfolios and then to rethink and retell how these learning stories contributed to their views of children’s learning identities.

The study found that learning stories have powerful effects on the ways children see themselves and on the ways those around them see the children as learners. It was clear from the data that children’s learning identities are embedded in the complex social and cultural contexts that surround them. The teachers’ long-term whanaungatanga relationships with mokopuna and whānau enabled kaiako to write learning stories that connected meaningfully with children’s wider historical, social, and cultural contexts. Insights into children’s learning from the learning stories were actively taken up by the parents and shaped the ways they saw and interacted with their children as learners. Likewise, teachers listened to stories shared from home (whether in a written learning story form or simply in the course of conversations), and these contributed to the teachers’ understandings of the children as agentic learners within sociocultural contexts. The physical folders of learning stories offered children powerful ways to maintain connections and a sense of pride in their learning achievements, linked to the people and places that surrounded those achievements.

Learning stories also enabled children to review their learning growth over time, including times when they had set goals, been supported in pursuing those goals by those around them, and had their achievements and dispositions honoured through documentation as a learning story. The process of robust engagement with crafting and reviewing their own and their colleagues’ learning stories played an important role in teachers’ ongoing professional learning. Finally, it was clear that across the whole community of practice—spanning mokopuna, whānau, and kaiako—learning stories played an important role in developing and reinforcing a shared language of learning as well as a shared understanding of the importance of children’s dispositions and working theories as the most highly valued forms of learning.

Although centred in one community, this research stands on the shoulders of many and may have resonance and implications for those in broader contexts. At a time when the usefulness and appropriateness of learning stories are increasingly contested, this study provides an important demonstration of the power of thoughtfully written learning stories and the alignment of this assessment approach with the vision and values of Te Whāriki. Further, with limited past research looking at the intersection of learning stories and children’s learning identities, this study’s rich account of this interaction in one community of practice provides a valuable contribution to the literature.

year: 2022