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Browsing Journal Articles by Author "Machaka, Ronald"

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Allotrope conversion and surface hardness increase in ion implanted boron nitride

Author: Derry, TE ; Lisema, LI ; Magabe, AT ; Aradi, E ; Machaka, Ronald ; Madhuku, M Date: Dec 2018 Previously, it has been shown that the implantation of hexagonal boron nitride with light ions (e.g. He+, Li+, B+) produces a surface layer containing nanoparticles of the much harder cubic form, as revealed by Raman spectroscopy, X-ray ... Read more
Analysis of the cold compaction behavior of titanium powders: a comprehensive inter-model comparison study of compaction equations

Author: Machaka, Ronald ; Chikwanda, HK Date: May 2015 A brief background to compaction equations and their application to titanium powder is presented. The behavior and mechanisms of densification in selected titanium powders is critically analyzed by means of a comprehensive inter-model comparison ... Read more
Capillary rheological studies of 17-4 PH MIM feedstocks prepared using a custom CSIR binder system

Author: Machaka, Ronald ; Ndlangamandla, P ; Seerane, Mandy N Date: Feb 2018 This paper reports on an attempt to establish the rheological properties of 17-4 PH stainless steel MIM feedstocks prepared using a proprietary CSIR wax-based binder system. The influence of powder and feedstock characteristics on the rheological ... Read more
Consolidation of titanium hydride powders during the production of titanium PM parts: The effect of die wall lubricants

Author: Machio, Christopher N ; Machaka, Ronald ; Chikwanda, HK Date: Nov 2015 The effects of die wall lubricants on the cold compaction of titanium hydride powder are studied. Three commonly-used die wall powder metallurgy lubricants – zinc stearate, Acrawax® C dispersion and Mirror Glaze® – are compared. The influence ... Read more
Dispersion characteristics, interfacial bonding and nanostructural evolution of MWCNT in Ti6Al4V powders prepared by shift speed ball milling technique

Author: Okoro, AM ; Machaka, Ronald ; Lephuthing, SS ; Awotunde, MA ; Oke, SR ; Falodun, OE ; Olubambi, PA Date: May 2019 The quest to achieve uniform dispersion of multiwalled carbon nanotubes (MWCNT) in metal matrices without compromising the structural integrity of the nanotubes during the production of metal matrix composites have been a lingering challenge ... Read more
The effect of Cr additions and oxidation on densification, microstructure, phase constituents and mechanical properties of TiAlCr alloys produced by SPS

Author: Mogale, N ; Matizamhuka, W ; Machaka, Ronald ; Shongwe, M ; Yamabe-Mitarai, Y Y Date: Jan 2021 Ternary Ti-47.5Al-(1–3)Cr (at. %) and reference quaternary Ti-48Al-2Cr-2Nb (at. %) titanium aluminide alloys were processed from elemental powders utilizing mechanical milling, mechanical alloying and spark plasma sintering. The effect of Cr ... Read more
Effect of Nb glue atom in the cluster formula on the microstructure and mechanical properties of Ti-Mo alloy

Author: Raganya, Mampai L ; Moshokoa, N ; Obadele, B ; Makhatha, E ; Machaka, Ronald Date: 2021 The effect of Nb in the glue site of the cluster-plus-glue atom model formula on the microstructure and mechanical properties of Ti-Mo alloy was investigated. Phase and microstructural analysis were performed by X-ray diffraction and electron ... Read more
The effect of solution treatment on the microstructure and mechanical properties of as-cast Ti-Mo alloys

Author: Moshokoa, Nthabiseng ; Raganya, Mampai L ; Obadele, BA ; Olubambi, PA ; Machaka, Ronald Date: 2020 The present study investigates the effect of solution treatment on the microstructure and mechanical properties of as-cast Ti-Mo alloys. The two alloys (Ti-8Mo and Ti-9Mo) were fabricated using a commercially available Arc re-melting furnace. ... Read more
Evaluating the Johanson theory for titanium powder

Author: Chikosha, S ; Machaka, Ronald ; Chikwanda, HK Date: May 2015 Direct powder rolling (DPR)/roll compaction has been labelled a complex and sample sensitive process. As such the design of the instrument and the determination of the optimal processing conditions for a given feed are very challenging. The ... Read more
Evaluating the Johanson theory for titanium powder

Author: Chikosha, S ; Machaka, Ronald ; Chikwanda, HK Date: May 2015 Direct powder rolling (DPR)/roll compaction has been labelled a complex and sample sensitive process. As such the design of the instrument and the determination of the optimal processing conditions for a given feed are very challenging. The ... Read more
An experimental evaluation of the Gerdemann–Jablonski compaction equation

Author: Machaka, Ronald ; Chikwanda, HK Date: May 2015 This paper reports on an attempt to independently evaluate the validity and applicability of a new compaction equation recently presented by Gerdemann and Jablonski [Metallurgical and Materials Transactions A, 42 (2011) 1325-1333] using ... Read more
The high-temperature performance of Ti-46.5Al-%xTa (x = 0.8, 4 and 8 at.%) alloys produced using SPS

Author: Cobbinah, PV ; Matizamhuka, W ; Machaka, Ronald ; Shongwe, MB ; Yanabe-Mitaria, Y Date: Jan 2021 In this study, -TiAl based alloys of composition Ti-46.5Al-%xTa (x = 0.8, 4 and 8 at.%) were fabricated by mechanical alloying and consolidated by spark plasma sintering. The main objective of the study was to evaluate the influence Ta contents ... Read more
The high-temperature performance of Ti-46.5Al-%xTa (x = 0.8, 4 and 8 at.%) alloys produced using SPS

Author: Cobbinah, PV ; Matizamhuka, W ; Machaka, Ronald ; Shongwe, MB ; Yanabe-Mitaria, Y Date: Jan 2021 In this study, -TiAl based alloys of composition Ti-46.5Al-%xTa (x = 0.8, 4 and 8 at.%) were fabricated by mechanical alloying and consolidated by spark plasma sintering. The main objective of the study was to evaluate the influence Ta contents ... Read more
The influence of particle size distribution on the properties of metal-injection-moulded 17-4 PH stainless steel

Author: Seerane, Mandy ; Ndlangamandla, P ; Machaka, Ronald Date: Oct 2016 Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final ... Read more
The influence of particle size distribution on the properties of metalinjection-moulded 17-4 PH stainless steel

Author: Seerane, Mandy N ; Ndlangamandla, P ; Machaka, Ronald Date: Oct 2016 Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final ... Read more
Investigation of the tensile properties of heat treated Ti-Mo alloys

Author: Raganya, Mampai L ; Moshokoa, Nthabiseng ; Obadele, BA ; Olubambi, PA ; Machaka, Ronald Date: 2020 Extensive efforts have been undertaken to develop Ti alloys consisting of single ß phase in order to substitute the a + ß phase in Ti-6Al-4V used as biomaterials. This study was aimed at investigating the tensile properties of solution treated ... Read more
Machine learning-based prediction of phases in high-entropy alloys

Author: Machaka, Ronald Date: Feb 2021 “The answer to the question “why HEAs exhibit such exceptional properties” lies in their phases” [1]. The implementation of machine learning (ML) approaches for the classification of solid solution high-entropy alloy (HEA) phases is, therefore, ... Read more
Machine learning-based prediction of phases in high-entropy alloys: A data article

Author: Machaka, Ronald ; Motsi, Glenda T ; Raganya, Mampai L ; Radingoana, Precious M ; Chikosha, Silethelwe Date: Oct 2021 A systematic framework for choosing the most determinant combination of predictor features and solving the multiclass phase classification problem associated with high-entropy alloy (HEA) was recently proposed [1]. The data associated with ... Read more c b n d
Mechanical and structural properties of fluorine-ion-implanted boron suboxide

Author: Machaka, Ronald ; Mwakikunga, Bonex W ; Manikandan, E ; Derry, TE ; Sigalas, I ; Herrmann, M Date: Sep 2011 Results on a systematic study on the effects of ion implantation on the near-surface mechanical and structural properties of boron suboxide (B6O) prepared by uniaxial hot pressing are reviewed. 150 keV fluorine ions at fluences of up to 5.0 ... Read more
Metal injection moulding of a 17-4 PH stainless steel: A comparative study of mechanical properties

Author: Machaka, Ronald Date: Oct 2018 While the metal injection moulding (MIM) of the precipitation-hardenable 17-4 PH stainless steel has found wide-ranging applications in a number of industries and popularity as a workhorse alloy, data on the as-sintered properties ‘that can ... Read more

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