title: Effect of Nb addition on the phase stability microstructure, and mechanical properties of powder metallurgy Ti-5Fe-xNb alloys

authors: Manogar, Balakrishnan

abstract: Ti alloys contemplating the simultaneous addition of Fe and Nb are available in the literature as Fe enhances the strength and Nb improves the biological behaviour of Ti. Nevertheless, casting has been the main manufacturing process, the Nb content is normally ≥10 wt.%, and no tensile properties are available. In this study, Ti-5Fe-xNb alloys (x = 2, 6, and 9 wt.%) were produced via powder metallurgy, which is more energy efficient than casting, with the aim of understanding the relationship between the mechanical behaviour and the microstructural changes brought about by the progressive addition of a greater amount of Nb. This study shows that the increment of the Nb content reduces the densification of the alloys, as the relative density decreases from 98.2% to 95.0%, but remarkably increases the volume fraction of the stabilised β phase (14→36%). Accordingly, the Ti-5Fe-xNb alloys are characterised by Widmanstätten microstructures, which become finer for higher Nb contents, and progressively higher mechanical properties including yield stress (725–949 MPa), ultimate tensile strength (828–995 MPa), and hardness (66.5–67.6 HRA), but lower elongation to fracture (4.0–5.1%). It is found that the ductility is much more influenced by the presence of the residual pores, whereas the strength greatly depends on the microstructural changes brought about by the addition of the alloying elements.

text: Effect of Nb addition on the phase stability microstructure, and mechanical properties of powder metallurgy Ti-5Fe-xNb alloys Ti alloys contemplating the simultaneous addition of Fe and Nb are available in the literature as Fe enhances the strength and Nb improves the biological behaviour of Ti. Nevertheless, casting has been the main manufacturing process, the Nb content is normally ≥10 wt.%, and no tensile properties are available. In this study, Ti-5Fe-xNb alloys (x = 2, 6, and 9 wt.%) were produced via powder metallurgy, which is more energy efficient than casting, with the aim of understanding the relationship between the mechanical behaviour and the microstructural changes brought about by the progressive addition of a greater amount of Nb. This study shows that the increment of the Nb content reduces the densification of the alloys, as the relative density decreases from 98.2% to 95.0%, but remarkably increases the volume fraction of the stabilised β phase (14→36%). Accordingly, the Ti-5Fe-xNb alloys are characterised by Widmanstätten microstructures, which become finer for higher Nb contents, and progressively higher mechanical properties including yield stress (725–949 MPa), ultimate tensile strength (828–995 MPa), and hardness (66.5–67.6 HRA), but lower elongation to fracture (4.0–5.1%). It is found that the ductility is much more influenced by the presence of the residual pores, whereas the strength greatly depends on the microstructural changes brought about by the addition of the alloying elements.

year: 2022-09-15

title: The prospectors’ claim at Te Aroha

authors: Hart, Philip

abstract: High up the mountain, on the edge of a precipice, the Prospectors’ Claim was at first examined only on the surface, producing some valuable stone. After the goldfield was proclaimed, two tunnels were driven under the supervision of experienced miners, but despite encouraging signs, no reef was struck. Once the first parcel was tested in Thames in early December, the owners realized the value of their ore was less than anticipated, and when a crushing was made in the new Te Aroha battery in 1881 the returns were lower than expected. Consequently, mining ceased, and the ground was abandoned. 
In September 1882 four experienced miners acquired part of the ground as the optimistically named Golden Hill, but after obtaining the usual ‘encouraging’ results their work came to nothing. There was some interest in the ground subsequently, but a lode was never found, and seemingly will never be found.

text: The prospectors’ claim at Te Aroha High up the mountain, on the edge of a precipice, the Prospectors’ Claim was at first examined only on the surface, producing some valuable stone. After the goldfield was proclaimed, two tunnels were driven under the supervision of experienced miners, but despite encouraging signs, no reef was struck. Once the first parcel was tested in Thames in early December, the owners realized the value of their ore was less than anticipated, and when a crushing was made in the new Te Aroha battery in 1881 the returns were lower than expected. Consequently, mining ceased, and the ground was abandoned. 
In September 1882 four experienced miners acquired part of the ground as the optimistically named Golden Hill, but after obtaining the usual ‘encouraging’ results their work came to nothing. There was some interest in the ground subsequently, but a lode was never found, and seemingly will never be found.

year: 2016

title: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2016

authors: Hicks, Brendan J.

abstract: The aim of the survey was to provide on-going monitoring of the fish communities and abundance by boat electrofishing in the Ohau Channel, especially fish species that are taonga to Maori (tuna, or eels, morihana, or goldfish, and kōura, or freshwater crayfish). In the current study, we present the findings from the tenth year of sampling (2016) and a summary of previous surveys.

text: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2016 The aim of the survey was to provide on-going monitoring of the fish communities and abundance by boat electrofishing in the Ohau Channel, especially fish species that are taonga to Maori (tuna, or eels, morihana, or goldfish, and kōura, or freshwater crayfish). In the current study, we present the findings from the tenth year of sampling (2016) and a summary of previous surveys.

year: 2017