title: Microstructure Dual-Refinement and Mechanical Properties Manipulation of TiBw/TA15(Si) Composites by Thermo-mechanical Processing and Heat Treatment

authors: Zhang, Rui

subjects: Titanium matrix composites

abstract: Titanium matrix composites with near-α titanium alloy as the matrix exhibit high specific strength and good high-temperature strength. However, the thermo-mechanical processing is limited by the brittleness of the reinforcement, making it difficult to refine the grain size and control the silicide precipitates. The present work aims to prepare titanium matrix composites with refined grain size and silicide particles. To this end, network-architecture TiBw/TA15(Si) composites were prepared using low-energy ball milling and vacuum hot-pressing. After refining the initial lamellar microstructure of the material through a solid solution treatment, the evolution of the TA15(Si) matrix and TiBw reinforcement during the hot deformation were studied. Ideal thermo-mechanical processing parameters in dual-phase region for TiBw/TA15(Si) composites after solid solution treatment was obtained, and the strain distribution in the compressive sample was revealed. Subsequently, TiBw/TA15(Si) composites with fine grains and dispersed silicide particles were obtained using solid solution treatment and isothermal hot-pressing, achieving a simultaneous improvement in room temperature strength and ductility. The influence mechanism of solid solution treatment on the microstructure and properties of the material was analyzed. Finally, TiBw/TA15(Si) composites with different lamellar content and morphologies were obtained through heat treatment of the deformed material. The effect of heat treatment on the microstructure of the material and the influence of different microstructures on the room temperature and high-temperature tensile mechanical behaviors of the material were discussed.
After compositional design through thermodynamic calculation, TiBw/TA15(Si) composites with different Si and Zr contents and a network architecture were prepared by low-energy ball milling and vacuum hot-pressing sintering using spherical TA15 coarse powder and TiB2, ZrB2, and Si fine powders. Silicide particles precipitated on the α/β interfaces in the matrix, and the precipitation amount increased with the increase of Si and Zr element contents. The tensile strength of materials with different compositions ranged from 1012 MPa to 1120 MPa, and the elongation ranged from 1.2% to 6.7%. When the Si content was between 0.3 wt.% and 1.0 wt.% and the Zr content was between 0.3 wt.% and 1.0 wt.%, the materials exhibited good strength and plasticity. By observing the microstructures of different materials subjected to heat treatment at 960°C to 1040°C for 30 min followed by quenching, it was found that silicide particles can be completely dissolved below β transformation temperature when the Si content is below 0.5 wt.%, which is suitable for microstructure control in dual-phase region. Considering the comprehensive mechanical properties and silicide dissolution temperature, a composite with a chemical composition of 3.4 vol.% TiBw/TA15-0.3 wt.%Si was selected for the study of dual-phase region thermo-mechanical processing and microstructure control.
After the solid solution treatment in single-phase region, the initial microstructure of TiBw/TA15(Si) was refined, after that, the high-temperature deformation behavior of the material was studied. The hot compression tests were conducted in dual-phase region at temperatures ranging from 870°C to 950°C and strain rates ranging from 1 s-1 to 0.001 s-1. It was found that the compressive stress-strain curves of the composite in this range exhibited dynamic recrystallization features, and the compressive stress decreased with increasing deformation temperature and decreasing strain rate. Except for the fully lath overheated-microstructure observed at 950°C / 1 s-1, the deformation microstructure of the material under the remaining conditions consisted of equiaxed α grains and residual α/β laths. The microstructure became finer with lower deformation temperature and higher strain rate. Higher recrystallization degree was observed below 910°C at lower strain rates, while the opposite was observed above 910°C. Observation of the microstructure produced by different deformation degrees revealed that the formation of equiaxed grains in the material involved three steps: α/β lath distortion, formation of boundaries within α/β laths, and lath decomposition. The activation energy for hot deformation of the TiBw/TA15(Si) composite after single-phase solid solution pretreatment was determined to be 623 kJ/mol. Based on the constructed processing map, the ideal deformation parameters were determined to be in the temperature range of 900°C to 950°C and strain rates of 0.01 s-1 to 0.001 s-1.
The orientation distribution of TiBw reinforcements during high-temperature plastic deformation in materials has been studied. The rotational behavior of TiBw reinforcements during deformation was analyzed, revealing that the orientation distribution of the reinforcements is influenced by the direction and magnitude of the principal strain applied to the material. The direction of the principal strain determines the principal directions of covariance matrix for the reinforcement's orientation distribution, while the magnitude of the principal strain determines the parameters in the probability density function. Based on these findings, a method was proposed to calculate the local plastic deformation in materials using the orientation distribution of TiBw reinforcements. Error analysis through computer simulations showed that this method exhibited good accuracy in the range of 20% to 80% compression strain. Using this method, the strain distribution in hot-deformed TiBw/TA15(Si) composites was analyzed, and the accuracy of the calculations was confirmed by comparing them with the deformation of the network structure of TiBw.
Based on the results of hot compression tests, TiBw/TA15(Si) composites were subjected to a solid solution treatment followed by isothermal hot pressing at 920 °C and a strain rate of 0.003 s-1 with 75% height reduction. This process yielded a microstructure with fine equiaxed α grains and dispersed fine silicide particles, with an average grain size of 1.6 μm and particle size of 70 μm, respectively, achieving a dual-refinement of both α grains and silicide particles. The composite exhibited a yield strength of 1100 MPa and an elongation of 7.7%. A comparison showed that the solid solution pretreatment led to finer grains and more dispersed silicide particles in the material after isothermal hot pressing, resulting in a significant increase in yield strength. 
Heat treatment of the hot-pressed composite in the range of 980 °C to 1050 °C revealed that higher temperatures led to higher contents of α/β laths and coarser microstructures, while faster cooling rates resulted in finer lath structures. Water quenching after the heat treatment at 1010 °C for 30 min produced excellent room temperature strength and ductility, with a tensile strength of 1350 MPa and an elongation of 6.7%. Slip trace analysis and transmission electron microscopy analysis revealed that the equiaxed microstructure in the material facilitated multi-system slip, enhancing deformation uniformity. The prismatic slip in lamellar microstructure obtained with air cooling was suppressed by the Burgers orientation relationship, the strain-softening of the lamellae resulted in deformation dominated by single-system slip and strain localization. The transformed β phase obtained through water quenching exhibited limited deformability, which was primarily accommodated by the prismatic slip of primary α laths. High-temperature tensile tests under different conditions showed that decreasing the deformation temperature, increasing the strain rate, refining the grain size, and decreasing the α/β lath content transform the deformation mechanism into grain boundary sliding, which significantly enhances the deformability of TiBw/TA15(Si) composites. The composite with fine equiaxed microstructure could achieve an elongation up to 348% at 800 °C and a strain rate of 0.0003 s-1, which showed a good potential for superplastic forming at low temperatures.

text: Microstructure Dual-Refinement and Mechanical Properties Manipulation of TiBw/TA15(Si) Composites by Thermo-mechanical Processing and Heat Treatment Titanium matrix composites with near-α titanium alloy as the matrix exhibit high specific strength and good high-temperature strength. However, the thermo-mechanical processing is limited by the brittleness of the reinforcement, making it difficult to refine the grain size and control the silicide precipitates. The present work aims to prepare titanium matrix composites with refined grain size and silicide particles. To this end, network-architecture TiBw/TA15(Si) composites were prepared using low-energy ball milling and vacuum hot-pressing. After refining the initial lamellar microstructure of the material through a solid solution treatment, the evolution of the TA15(Si) matrix and TiBw reinforcement during the hot deformation were studied. Ideal thermo-mechanical processing parameters in dual-phase region for TiBw/TA15(Si) composites after solid solution treatment was obtained, and the strain distribution in the compressive sample was revealed. Subsequently, TiBw/TA15(Si) composites with fine grains and dispersed silicide particles were obtained using solid solution treatment and isothermal hot-pressing, achieving a simultaneous improvement in room temperature strength and ductility. The influence mechanism of solid solution treatment on the microstructure and properties of the material was analyzed. Finally, TiBw/TA15(Si) composites with different lamellar content and morphologies were obtained through heat treatment of the deformed material. The effect of heat treatment on the microstructure of the material and the influence of different microstructures on the room temperature and high-temperature tensile mechanical behaviors of the material were discussed.
After compositional design through thermodynamic calculation, TiBw/TA15(Si) composites with different Si and Zr contents and a network architecture were prepared by low-energy ball milling and vacuum hot-pressing sintering using spherical TA15 coarse powder and TiB2, ZrB2, and Si fine powders. Silicide particles precipitated on the α/β interfaces in the matrix, and the precipitation amount increased with the increase of Si and Zr element contents. The tensile strength of materials with different compositions ranged from 1012 MPa to 1120 MPa, and the elongation ranged from 1.2% to 6.7%. When the Si content was between 0.3 wt.% and 1.0 wt.% and the Zr content was between 0.3 wt.% and 1.0 wt.%, the materials exhibited good strength and plasticity. By observing the microstructures of different materials subjected to heat treatment at 960°C to 1040°C for 30 min followed by quenching, it was found that silicide particles can be completely dissolved below β transformation temperature when the Si content is below 0.5 wt.%, which is suitable for microstructure control in dual-phase region. Considering the comprehensive mechanical properties and silicide dissolution temperature, a composite with a chemical composition of 3.4 vol.% TiBw/TA15-0.3 wt.%Si was selected for the study of dual-phase region thermo-mechanical processing and microstructure control.
After the solid solution treatment in single-phase region, the initial microstructure of TiBw/TA15(Si) was refined, after that, the high-temperature deformation behavior of the material was studied. The hot compression tests were conducted in dual-phase region at temperatures ranging from 870°C to 950°C and strain rates ranging from 1 s-1 to 0.001 s-1. It was found that the compressive stress-strain curves of the composite in this range exhibited dynamic recrystallization features, and the compressive stress decreased with increasing deformation temperature and decreasing strain rate. Except for the fully lath overheated-microstructure observed at 950°C / 1 s-1, the deformation microstructure of the material under the remaining conditions consisted of equiaxed α grains and residual α/β laths. The microstructure became finer with lower deformation temperature and higher strain rate. Higher recrystallization degree was observed below 910°C at lower strain rates, while the opposite was observed above 910°C. Observation of the microstructure produced by different deformation degrees revealed that the formation of equiaxed grains in the material involved three steps: α/β lath distortion, formation of boundaries within α/β laths, and lath decomposition. The activation energy for hot deformation of the TiBw/TA15(Si) composite after single-phase solid solution pretreatment was determined to be 623 kJ/mol. Based on the constructed processing map, the ideal deformation parameters were determined to be in the temperature range of 900°C to 950°C and strain rates of 0.01 s-1 to 0.001 s-1.
The orientation distribution of TiBw reinforcements during high-temperature plastic deformation in materials has been studied. The rotational behavior of TiBw reinforcements during deformation was analyzed, revealing that the orientation distribution of the reinforcements is influenced by the direction and magnitude of the principal strain applied to the material. The direction of the principal strain determines the principal directions of covariance matrix for the reinforcement's orientation distribution, while the magnitude of the principal strain determines the parameters in the probability density function. Based on these findings, a method was proposed to calculate the local plastic deformation in materials using the orientation distribution of TiBw reinforcements. Error analysis through computer simulations showed that this method exhibited good accuracy in the range of 20% to 80% compression strain. Using this method, the strain distribution in hot-deformed TiBw/TA15(Si) composites was analyzed, and the accuracy of the calculations was confirmed by comparing them with the deformation of the network structure of TiBw.
Based on the results of hot compression tests, TiBw/TA15(Si) composites were subjected to a solid solution treatment followed by isothermal hot pressing at 920 °C and a strain rate of 0.003 s-1 with 75% height reduction. This process yielded a microstructure with fine equiaxed α grains and dispersed fine silicide particles, with an average grain size of 1.6 μm and particle size of 70 μm, respectively, achieving a dual-refinement of both α grains and silicide particles. The composite exhibited a yield strength of 1100 MPa and an elongation of 7.7%. A comparison showed that the solid solution pretreatment led to finer grains and more dispersed silicide particles in the material after isothermal hot pressing, resulting in a significant increase in yield strength. 
Heat treatment of the hot-pressed composite in the range of 980 °C to 1050 °C revealed that higher temperatures led to higher contents of α/β laths and coarser microstructures, while faster cooling rates resulted in finer lath structures. Water quenching after the heat treatment at 1010 °C for 30 min produced excellent room temperature strength and ductility, with a tensile strength of 1350 MPa and an elongation of 6.7%. Slip trace analysis and transmission electron microscopy analysis revealed that the equiaxed microstructure in the material facilitated multi-system slip, enhancing deformation uniformity. The prismatic slip in lamellar microstructure obtained with air cooling was suppressed by the Burgers orientation relationship, the strain-softening of the lamellae resulted in deformation dominated by single-system slip and strain localization. The transformed β phase obtained through water quenching exhibited limited deformability, which was primarily accommodated by the prismatic slip of primary α laths. High-temperature tensile tests under different conditions showed that decreasing the deformation temperature, increasing the strain rate, refining the grain size, and decreasing the α/β lath content transform the deformation mechanism into grain boundary sliding, which significantly enhances the deformability of TiBw/TA15(Si) composites. The composite with fine equiaxed microstructure could achieve an elongation up to 348% at 800 °C and a strain rate of 0.0003 s-1, which showed a good potential for superplastic forming at low temperatures.

year: 2024

title: Stratigraphy and sedimentology of Pliocene limestones in northern Hawke's Bay: The Opoiti, Whakapunake and Tahaenui Limestones

authors: Drinnan, Michele Maree

subjects: limestone

abstract: The Opoiti, Whakapunake and Tahaenui Limestone formations (Opoitian to Waipipian; Pliocene) crop out extensively in northern Hawke’s Bay between Wairoa and Mahia Peninsula where they are encased within mudstone dominated Wairoa Formation. The limestones are shallow cool-water carbonates that formed about tectonically active antiform structures inboard from the convergent subduction plate margin along eastern North Island. Their coarse skeletal fraction is dominated by barnacle plates with common brachiopod, pectinid and oyster remains. The carbonate factory for prolific skeletal production was likely sited in shoal water (30-60 m deep), high energy conditions atop the antiforms, with deposition from carbonate shedding down the flanks of the antiforms and even into the bounding synforms.

The individual limestone units are laterally discontinuous and perceived as large lenses (up to c.3-4 km long by c.2 km wide). The enclosing thick mud-rich (M1-M4) to locally sandy (S1-S4) lithofacies, along with occasional volcaniclastic beds (V1), are here informally recorded as Wairoa Formation A, B, C or D, depending on their stratigraphic position with respect to the three limestone units.

Stratigraphic logging of sections at Nuhaka (Tahaenui/Clonkeen), Mt Moumoukai and on Mahia Peninsula established 12 sedimentary lithofacies based on field texture and composition, namely limestones (L1-L3), sandstones (S1-S4), mudstones (M1-M4), and a volcaniclastite (V1). The lithofacies discriminate well on triangular plots involving carbonate content and insoluble sand, silt and clay grain sizes and typically show vertical similarities between field sites for each limestone, suggestive of similar depositional patterns and controls operating at the different localities.

Opoiti Limestone occurs on Mahia Peninsula and Mt Moumoukai as a bedded, c.30 m thick, moderately dipping (25° W), siliciclastic sand-rich unit with common brachiopods and mudstone clasts (L1, L2, L3) that unconformably overlies late Miocene mudstone (M1). Petrography ranges from a sandy biomicrite to a variably sandy, poorly washed rounded biosparite or bioclastic arenite in which interskeletal space is occupied mainly by microbioclastic micrite with some isopachous sparite. Carbonate content is up to c.75%; siliciclastic grains range from very fine to fine sand size. The Opoiti Limestone is likely a transgressive event deposit (TST), fining upwards into sandstone and mudstone (HST) of Wairoa Formation B, and largely under tectonic control.

Whakapunake Limestone within the field area is restricted to the west coast of Mahia Peninsula where it is c.40 m thick and comprises limestone (L3) units (10- 100 cm thick) interbedded with unique mudclast-bearing shelly sandstone (S4) units (20-100 cm thick). These couplets may be related to storm emplacements although their origin, and that of the mudclasts, remains problematic. The elongated mudclasts possibly mark the positions of original Skolithos/Ophiomorpha-like burrows that have been later modified by seismic shaking. No lower contact was observed. Upwards, the limestone grades via interbeds into shelly sandstone (S2) and mudstone (M1). Petrography ranges from packed biomicrites to poorly washed biosparites, while the sandstone interbeds are typically muddy bioclastic arenites. Cements are isopachous sparite rims and microbioclastic micrite with common siliciclasts. Carbonate contents range up to c.70% with the siliciclastic grains being of medium silt and fine sand size. The Whakapunake Limestone is likely a transgressive deposit (TST) fining upwards into shelly sandstone (TST/HST) of Wairoa Formation C, again overall tectonically driven but with possible superimposed eustatic sea level changes.

Tahaenui Limestone (L1, L3) occurs in discrete outcrops (10-30 m thick) across the full area. At Nuhaka, it unconformably overlies late Miocene mudstone (M1), while the upper contact grades into shelly sandstone (S2). At Moumoukai, it unconformably onlaps the Opoiti Limestone. It is dominated by coarse barnacle plates with interparticle isopachous sparite rims and microbioclastic micrite. Petrographically the limestone ranges from rounded biosparite to packed biomicrite. Carbonate content is up to 90%, with the siliciclastic grains being of fine-medium silt and fine sand size. The Tahaenui Limestone is overall a transgressive deposit (TST) fining upwards into shelly sandstone and mudstone (HST) of Wairoa Formation D, largely under tectonic control.

The Pliocene limestones are economically important as potential subsurface petroleum reservoirs, as a lime resource for agricultural use and as a hard stone source for aggregate. Recommendations of the immediate economic potential for development include local aggregate and fertiliser sources from the Tahaenui Limestone at Nuhaka and Mahia.

text: Stratigraphy and sedimentology of Pliocene limestones in northern Hawke's Bay: The Opoiti, Whakapunake and Tahaenui Limestones The Opoiti, Whakapunake and Tahaenui Limestone formations (Opoitian to Waipipian; Pliocene) crop out extensively in northern Hawke’s Bay between Wairoa and Mahia Peninsula where they are encased within mudstone dominated Wairoa Formation. The limestones are shallow cool-water carbonates that formed about tectonically active antiform structures inboard from the convergent subduction plate margin along eastern North Island. Their coarse skeletal fraction is dominated by barnacle plates with common brachiopod, pectinid and oyster remains. The carbonate factory for prolific skeletal production was likely sited in shoal water (30-60 m deep), high energy conditions atop the antiforms, with deposition from carbonate shedding down the flanks of the antiforms and even into the bounding synforms.

The individual limestone units are laterally discontinuous and perceived as large lenses (up to c.3-4 km long by c.2 km wide). The enclosing thick mud-rich (M1-M4) to locally sandy (S1-S4) lithofacies, along with occasional volcaniclastic beds (V1), are here informally recorded as Wairoa Formation A, B, C or D, depending on their stratigraphic position with respect to the three limestone units.

Stratigraphic logging of sections at Nuhaka (Tahaenui/Clonkeen), Mt Moumoukai and on Mahia Peninsula established 12 sedimentary lithofacies based on field texture and composition, namely limestones (L1-L3), sandstones (S1-S4), mudstones (M1-M4), and a volcaniclastite (V1). The lithofacies discriminate well on triangular plots involving carbonate content and insoluble sand, silt and clay grain sizes and typically show vertical similarities between field sites for each limestone, suggestive of similar depositional patterns and controls operating at the different localities.

Opoiti Limestone occurs on Mahia Peninsula and Mt Moumoukai as a bedded, c.30 m thick, moderately dipping (25° W), siliciclastic sand-rich unit with common brachiopods and mudstone clasts (L1, L2, L3) that unconformably overlies late Miocene mudstone (M1). Petrography ranges from a sandy biomicrite to a variably sandy, poorly washed rounded biosparite or bioclastic arenite in which interskeletal space is occupied mainly by microbioclastic micrite with some isopachous sparite. Carbonate content is up to c.75%; siliciclastic grains range from very fine to fine sand size. The Opoiti Limestone is likely a transgressive event deposit (TST), fining upwards into sandstone and mudstone (HST) of Wairoa Formation B, and largely under tectonic control.

Whakapunake Limestone within the field area is restricted to the west coast of Mahia Peninsula where it is c.40 m thick and comprises limestone (L3) units (10- 100 cm thick) interbedded with unique mudclast-bearing shelly sandstone (S4) units (20-100 cm thick). These couplets may be related to storm emplacements although their origin, and that of the mudclasts, remains problematic. The elongated mudclasts possibly mark the positions of original Skolithos/Ophiomorpha-like burrows that have been later modified by seismic shaking. No lower contact was observed. Upwards, the limestone grades via interbeds into shelly sandstone (S2) and mudstone (M1). Petrography ranges from packed biomicrites to poorly washed biosparites, while the sandstone interbeds are typically muddy bioclastic arenites. Cements are isopachous sparite rims and microbioclastic micrite with common siliciclasts. Carbonate contents range up to c.70% with the siliciclastic grains being of medium silt and fine sand size. The Whakapunake Limestone is likely a transgressive deposit (TST) fining upwards into shelly sandstone (TST/HST) of Wairoa Formation C, again overall tectonically driven but with possible superimposed eustatic sea level changes.

Tahaenui Limestone (L1, L3) occurs in discrete outcrops (10-30 m thick) across the full area. At Nuhaka, it unconformably overlies late Miocene mudstone (M1), while the upper contact grades into shelly sandstone (S2). At Moumoukai, it unconformably onlaps the Opoiti Limestone. It is dominated by coarse barnacle plates with interparticle isopachous sparite rims and microbioclastic micrite. Petrographically the limestone ranges from rounded biosparite to packed biomicrite. Carbonate content is up to 90%, with the siliciclastic grains being of fine-medium silt and fine sand size. The Tahaenui Limestone is overall a transgressive deposit (TST) fining upwards into shelly sandstone and mudstone (HST) of Wairoa Formation D, largely under tectonic control.

The Pliocene limestones are economically important as potential subsurface petroleum reservoirs, as a lime resource for agricultural use and as a hard stone source for aggregate. Recommendations of the immediate economic potential for development include local aggregate and fertiliser sources from the Tahaenui Limestone at Nuhaka and Mahia.

year: 2011

title: Young Māori mothers and bed-sharing with their pēpi/baby: A case study focusing on the relevance and influence of three varying health promotion resources

authors: Haereroa, Nikki M.

subjects: Māori

abstract: Māori Sudden Unexpected Death in Infancy (SUDI) rates are significantly higher than non-Māori. Bed-sharing is considered to be one of the major modifiable risk factors associated with SUDI rates (Mitchell et al., 1992), although there is strong opposition that suggests bed-sharing can act as a preventative measure against SUDI (McKenna & McDade, 2005). As a result of quantitative research and statistical data, many health promotion messages now focus on discouraging the practice of bed-sharing, whether it be through policy implementation throughout hospitals or through to health promotion guidelines. Although there is a high incidence of Māori SUDI rates, there has been little emphasis on Māori perspectives and insights into the practice. Of the few qualitative studies that focus on infant sleep practices, a significant finding is the high prevalence of Māori who bed-share regularly (Tipene-Leach et al., 2010). This paper will investigate the motivations and rationale of bed-sharing amongst young urban Māori mothers to gain a deeper understanding and appreciation into the lived realities of this group. The lack of consultation with a group that has been classed by New Zealand Government bodies, the Health Quality and Safety Commission and Child and Youth Mortality Review Committee Group, as ‘most at risk’ of experiencing a SUDI, maybe a contributing factor to the high Māori SUDI rates. This has brought about the question of whether current health resources are relevant and/or influence young Māori mothers. Using a Te Whare Tapa Wha framework within a Kaupapa Māori Research methodology, this paper provides a unique and much-needed perspective into the lives of young Māori mothers. The purpose of this research overall is: if health resources and messages are not relevant to a community and they have little or no influence over infant care practices, then do health professionals and researchers need to rethink current strategies and working models to ensure we focus on the real, lived needs of our community?

text: Young Māori mothers and bed-sharing with their pēpi/baby: A case study focusing on the relevance and influence of three varying health promotion resources Māori Sudden Unexpected Death in Infancy (SUDI) rates are significantly higher than non-Māori. Bed-sharing is considered to be one of the major modifiable risk factors associated with SUDI rates (Mitchell et al., 1992), although there is strong opposition that suggests bed-sharing can act as a preventative measure against SUDI (McKenna & McDade, 2005). As a result of quantitative research and statistical data, many health promotion messages now focus on discouraging the practice of bed-sharing, whether it be through policy implementation throughout hospitals or through to health promotion guidelines. Although there is a high incidence of Māori SUDI rates, there has been little emphasis on Māori perspectives and insights into the practice. Of the few qualitative studies that focus on infant sleep practices, a significant finding is the high prevalence of Māori who bed-share regularly (Tipene-Leach et al., 2010). This paper will investigate the motivations and rationale of bed-sharing amongst young urban Māori mothers to gain a deeper understanding and appreciation into the lived realities of this group. The lack of consultation with a group that has been classed by New Zealand Government bodies, the Health Quality and Safety Commission and Child and Youth Mortality Review Committee Group, as ‘most at risk’ of experiencing a SUDI, maybe a contributing factor to the high Māori SUDI rates. This has brought about the question of whether current health resources are relevant and/or influence young Māori mothers. Using a Te Whare Tapa Wha framework within a Kaupapa Māori Research methodology, this paper provides a unique and much-needed perspective into the lives of young Māori mothers. The purpose of this research overall is: if health resources and messages are not relevant to a community and they have little or no influence over infant care practices, then do health professionals and researchers need to rethink current strategies and working models to ensure we focus on the real, lived needs of our community?

year: 2015