bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving the quality of aircraft fasteners by transverse running with flat plates
Authors: Zaides S A , Kh Kuang L 
Published: November 2019

Abstract
For the strain hardening of aircraft fasteners, a surface plastic deformation method is proposed, based on running of blanks with smooth plates. The method allows processing parts that do not have center holes. Transverse running also eliminates the bending of the workpiece from the transverse loading forces action. Analytical dependences are obtained for determining the maximum possible contact area and relative compression for a transverse running. The quality of fasteners after transverse running with smooth plates provides the following favorable changes in the surface layer of metal: the formation of residual compressive stresses in the surface layers, a significant decrease in the initial roughness, an increase in the microhardness of the surface layer, the formation of a fine-grained structure, and the high accuracy of the machined parts diameter.
The effect of cast structures on texture and mechanical properties of AISI 433 ferritic stainless steel
Authors: Maumela M , Stumpf W E , Siyasiya C W 
Published: November 2019

Abstract
The influence of the individual equiaxed and columnar cast structure on the evolution of texture during thermo-mechanical processes (TMP) was investigated using the electron backscatter diffraction (EBSD) technique. The recrystallization texture after cold working and annealing was then related to mechanical properties of the initial cast structures. It was found that the initial equiaxed cast structure exhibited a homogenous γ-fiber texture while the columnar developed an inhomogeneous texture with the predominance of both the Goss and α-fiber textures. While texture has a significant influence on surface smoothness of the drawn product, it was found that it did not significantly affect the yield strength and ultimate tensile strength (UTS), but marginally affected the elongation i.e. it was found to be slighted higher for the equiaxed than the columnar cast structure measured parallel to the rolling direction (RD).
Effect of the quench temperature on the mechanical properties of a medium C Mn high Si steel during Q&P heat treatment process
Authors: Kurup V , Siyasiya C W , Mostert R J 
Published: November 2019

Abstract
A steel of composition Fe-0.2C-3Mn-2Si-0.5Al was fully austenized followed by a quench and partitioning heat treatment process (Q&P). The quench temperature was varied, which resulted in different volume fractions of retained austenite (RA) and martensite. Analysis of the phase evolution and the resulting microstructures during the Q&P process were carried out using different techniques namely, - dilatometry, FEG SEM, EBSD, and neutron diffraction. Mechanical properties were evaluated by standard tensile tests on samples quenched to different temperatures. The partitioning process was evaluated by dilatometry. The volume fraction of the RA was determined by neutron diffraction. It was found that the volume fraction of RA increased with an increase in the quench temperature contrary to the Speer model. It was also observed that the presence of bainite, which formed during the quench and partitioning temperature significantly stabilized the RA by carbon partitioning. The tensile test results indicated the optimum quench temperature for the best combination of strength and ductility and contrary to expectation, this did not occur in the specimen with the maximum amount of RA. In other words, the mechanical properties of the steel undergoing a Q&P process is influenced by the quench temperatures and is also affected the phase evolution which occurs during both the quench and partitioning process.
Major determinant of service life in magnesia-graphite slagline refractory lining in secondary steelmaking ladle furnace
Authors: Otunniyi I O , Theko Z V , Mokoena B L E , Maramba B 
Published: November 2019

Abstract
Magnesia-carbon (MgO-C) refractory bricks are used for slagline lining in secondary steelmaking to withstand the harsh basic slag and high temperature environment. In an operation using bottom purging ladle furnaces, preliminary study of residual bricks after lining failures shows less than 50 vol. % of the MgO-C bricks is typically used before the linings would fail. Slag basicity, high temperature oxidation and erosion are known as root causes of different degradation modes in this application. This work, presented in part herein, seeks to identify the dominant cause for this resource utilization inefficiency. Slag basicity excursions and thermal fluctuations versus service lives and residual thicknesses of each MgO-C brick after lining failure, were studied for five ladle linings. Optical and electron microscopy were also used in further post-mortem of the residual bricks. The operation data that showed thermal spikes above 1600 °C and acidic slags with basicity usually below the ideal of 1.67. Micrographs from the slag-refractory interfaces indicated effect of this operational extremes showing thermal shock cracking, slag penetration and evolution of phase due to the slag-refractory interactions. However, bricks evidencing these effects were not the most worn. Slag basicity attack and high temperature oxidations are diffusion controlled and did not proceed aggressively by themselves. Rather, least residual thicknesses were found in bricks from columns adjacent to the two purging gas entry points at the bottom of the ladle. Up to 86 % wear were obtained at such points, in contrast to 24 % for bricks farthest from this effect. Turbulence from the purging gas is thus responsible for localized and highest lining consumption rate that decimates lining life in these ladles. Without this purging turbulence, such as in induction stirring, it can be projected that the lining life can triple, with obvious economics and environmental advantages. While the MgO-C refractory is well able to withstand the chemical and thermal extremes of secondary steelmaking slag environment, bottom purging ladle furnace design deserves a review to improve refractory utilization.
Effect of intercritical annealing of normalised Nb-Ti-V microalloyed plate steel on microstructural evolution
Authors: Kambilinya PI , Siyasiya CW , Banks KM , Mostert RJ 
Published: November 2019

Abstract
A homogeneous microstructure is required for consistent mechanical properties in normalised Nb-Ti-V microalloyed plate steels. Frequently, as-hot rolled microalloyed plate steels have a banded microstructure that is persistent even after normalising heat treatment (NHT), and this leads to inconsistencies and some scatter in mechanical properties. Therefore, this work focused on the influence of single-cycle normalising heat treatment (SNHT), double-cycle normalising heat treatment (DNHT) followed by intercritical annealing normalising heat treatment (INHT) on the homogenisation and mitigation of a banded microstructure. The study was conducted on a 0.13C-Nb-Ti-V plate steel grade. The as-hot rolled microstructure was banded and had a 1.13 Anisotropy Index (AI) value. Results from the three thermal cycles revealed that the DNHT and INHT mitigated the pearlite microstructural banding and gave a more homogenized pearlite phase distribution throughout the microstructure, unlike the SNHT that retained the banding. The DNHT also exhibited the finest ferrite grain size, while the INHT exhibited the coarsest. From Vickers hardness measurements (153±5.8 HV, 157±3.6 HV and 166±4.5 HV), the UTS was approximately deduced as, 480, 490 and 530 MPa for the SNHT, DNHT and INHT respectively.
Development of lining materials for reactor vessel used in the CSIR titanium process
Authors: Sehoana M P , Fazluddin S 
Published: November 2019

Abstract
The CSIR Titanium powder process is a high temperature’ molten salt/alkali metal titanium production process. The aim of this process is to produce titanium powder of high purity and quality that meets the specifications for commercially-pure powder. The quality of CSIR Ti-powder produced to date shows in general that there are challenges when it comes to meeting this requirement. Two of the main challenges is the reagents used employed in the process and by-products formed which are highly corrosive. These corrosive agents promote corrosion of the reactor with the corrosion product then being introduced as impurities in the titanium powder. A project to investigate lining materials to protect the vessel from corrosion and preserve product quality and purity was thus initiated. This article gives an in-depth insight into the corrosion resistance properties of different metals that can be investigated as a potential lining material in molten lithium and molten lithium chloride environment.
EBSD characterisation of the B2 orientation in γ-TiAl based alloy
Authors: Mathabathe M N , Bolokang A S , Govender G , Siyasiya C W , Mostert R J 
Published: November 2019

Abstract
Electron backscattered diffraction (EBSD) has been conducted to determine the orientation relationship of the remnant B2 phase in an α-solidified γ-Ti-45Al-2Nb-0.3Si (at. %) based intermetallic alloy. The morphology and microstructural characterisation was investigated using conventional methods. The results showed that the B2-grains exhibits a Blackburn orientation relationship (BOR) with the α2 grains viz. {111}B2 // {0001}α2 and {110}B2 // {11-20}α2. Moreover, mis-orientation axes of B2-grains were found in the clusters between <101> and <111> in 57-63° angles, in the Y0 directions. In addition, it was also observed that the overall B2 grains in the alloy structure was textured and comprised of high angle boundaries of misorientations above 15° angles.
Microstructure characterisation and microhardness of P92 steel heat treated at the transformation temperatures
Authors: Obiko J , Chown L H , Whitefield D J 
Published: November 2019

Abstract
Modern power plant components for the transport of superheated steam are manufactured from creep resistant steels, such as ASTM grade P92, that have microstructural stability and excellent mechanical properties at high temperature and pressure. Before application as pipes, tubes and connectors, P92 steel undergoes a heat treatment of austenitisation and tempering to achieve a tempered martensite microstructure, with carbides along the prior austenite grain boundaries and carbonitrides within the matrix. In the power plant, pipes and tubes are joined by welding, inducing residual stresses and inhomogeneous microstructures in the weld joint, which reduce creep resistance. As in most steels, the temperature gradient from the fusion line to the base metal leads to different microstructural zones in the weld joint. The fine-grained heat affected zone (FGHAZ), which forms at temperatures near the transformation region, acts as a weak zone for Type IV cracking during creep. The lower and upper critical transformation temperatures for the P92 steel in this work are 800°C-850°C (Ae1) and 900°C-950°C (Ae3) respectively. As-received samples were heated to temperatures of 830, 850, 900°C to simulate the fine grain heat affected zone, or the very high temperature of 1200°C to simulate the coarse grain heat affected zone (CGHAZ), held at that temperature for 90 minutes and then tempered at 730°C to 780°C for 120 minutes. The microstructures before and after heat treatment were observed by scanning electron microscopy and optical microscopy, and Vickers microhardness measurements were done. After tempering, coarse carbides were seen on the prior austenite grain boundaries (PAGBs) and nitrides were observed in the matrix. In general, the hardness increased with an increase in the austenitisation and tempering temperature combination.
Effect of Temperature on Densification, Microstructural Evolution and Mechanical Properties of Ti-5Al-1Mo Developed via Spark Plasma Sintering
Authors: Jeje S O , Shongwe M B , Maledi N , Rominiyi A L , Babalola B J , Lepele P F 
Published: November 2019

Abstract
Titanium alloys are ideally suited for advanced aerospace structures and industrial applications because of the combination of high strength, low density, good toughness, stiffness, and good corrosion resistance at cryogenic to elevated temperatures. This paper investigates the effect of temperature on alloy densification, microstructure evolution and mechanical properties of Ti-5Al-1Mo processed by Spark Plasma Sintering (SPS). Ti, Al, Mo elemental powders with 94, 5 and 1 wt.% respectively were mixed thoroughly for 8 hrs to attain homogeneity. The mixed powders were consolidated at sintering temperature of 800°C, 1000 °C, 1100 °C, pressure of 50 MPa, holding time of 10 min, and sintering rate of 100 °C/min. The compacted samples were characterised using scanning electron microscopy (SEM), equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry techniques. Compacts hardness was also investigated using Vickers micro-hardness tester. Almost fully densified compacts were obtained for samples sintered at 1000 °C and 1100 °C, the microstructures show that the sintered compacts are chemically homogeneous with the Al fully diffused into the CP-Ti matrix. The microhardness increases with increasing temperature with the maximum value being 290.35 HV.
Effect of particle size distribution on green properties and sintering of Ti-6Al-4V
Authors: Ramabulana K , Tambani M , Machio C , Makhatha M E 
Published: November 2019

Abstract
In this study, the conventional powder metallurgy route of pressing and sintering was employed to study the effects of the particle size of blended elemental Ti-6Al-4V powders on the properties of powder mixtures, green and sintered densities. The -45 μm and -150 μm 60Al-40V master alloy powder were blended with the titanium powder to produce the -45 μm and -150 μm Ti-6Al-4V blend. Powders were pressed at 580 to 870 MPa and sintered in a tube furnace. Taguchi method was used to optimise the sintering parameters, temperature and time, and ANOVA was employed to determine the significant parameters and their contribution to the sintered density. The optimum parameters maximising the density were found to be sintering temperature of 1300 °C and sintering time of 180 mins, for both particle sizes. The green density was higher for the coarser powder and the sintered density was higher for the finer powder.
Biocompatibility Study of Ti-based Alloys Fabricated by Spark Plasma Sintering
Authors: Mahundla M R , Matizamhuka W R , Machaka R , Yamamoto A , Shongwe M B 
Published: November 2019

Abstract
Titanium (Ti) alloys often find their way in orthopaedic applications owing to their superior mechanical properties, biocompatibility, corrosion resistance and low Young’s modulus. Nano/sub-micron grain structured commercially pure titanium (CP Ti), Ti-6Al-4V (Ti-64) and Ti-34Nb-25Zr (TNZ) alloys were fabricated via mechanical alloying (MA) of elemental powders followed by spark-plasma sintering (SPS). The powders were milled at 500rpm for 5h and sintered at a temperature of 1200°C, heating rate of 100°C/min, dwelling time of 10min and a pressure of 50MPa. The sintered samples were metallographically prepared to a mirror finish surface in 5:2 ratio of colloidal silica and hydrogen peroxide (H2O2) mixture. Biocompatibility tests were conducted by water soluble tetrazolium and 1-methoxy phenazinium methylsufate (WST-1 PMS) with sarcoma osteogenetic-2 (SaOS-2) human cell line. High cell proliferation on Ti and Ti-64 was observed after 1 and 4 days of incubation. After 7 days, proliferation on Ti-64 was the highest followed by Ti. However, TNZ alloy have less cell proliferation through the entire period of incubation.
Fibronectin adsorption is less for Ti and TNZ compared to and Ti-64. In decreasing order albumin adsorption was highest on Ti than TNZ alloy followed by less adsorption on Ti-64. Surface wettability of Ti and Ti-64 showed a high contact angle of between 93-98° compared to 86° TNZ alloy. The surface wettability results correlated well to less fibronectin adsorption on Ti-34Nb-25Zr alloy and highest for Ti-6Al-4V. The Ti-34Nb-25Zr showed less cell proliferation which is believed to be linked with fibronectin adsorption results.
Development of a biocompatible Ti-Nb alloy for orthopaedic applications
Authors: Fikeni L , Annan K A , Seerane M , Mutombo K , Machaka R 
Published: November 2019

Abstract
Metallic biomedical implants such as titanium-based alloys are very useful for orthopaedic applications due to their excellent properties which responds to changes in temperature and other conditions. However, biological toxicity due to alloying elements and relatively high Young’s modulus or mechanical incompatibilities of previously used Ti alloys have necessitated the development of biocompatible alloys with compatible mechanical properties such as beta-titanium alloys. This study aims at production of beta-titanium alloy with enhanced properties by varying milling speeds. Ti and Nb powders were mechanically alloyed using the high energy ball-mill Zoz-Simoloyer® to produce Ti-7Nb alloys by varying the milling speed. The milling process produced irregular shaped powders with increasing particles sizes as the milling speed increased due to fragmentation and cold welding during agglomeration. The mechanical alloying process had good yield. The predominant phases of the inhomogeneously milled alloy were alpha and beta phases.
Influence of spark plasma sintering temperature on the densification and micro-hardness behaviour of Ni-Cr-Al alloy
Authors: Babalola B J , Shongwe M B , Jeje S O , Rominiyi A L , Ayodele O O , Olubambi P A 
Published: November 2019

Abstract
Sintering temperature is essential towards attaining desired densification and formation of phases which in turn influences the microstructure and properties of a material. In this study, the densification and microhardness behaviour of Ni-Cr-Al alloy prepared by spark plasma sintering (SPS) at different sintering temperatures were investigated. After sintering operation, the density, hardness, phase analysis, and microstructural evolution were investigated using the Archimede’s principle, hardness tester, X-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The nickel based alloy was sintered at temperatures of 600, 750, 950 and 1100 °C. The results indicated that the densification, microstructure, and hardness values were influenced by changes in the sintering temperature. The relative density increased from 73.89 % at 600 °C to 99.89 % at 1100 °C, while the hardness value was enhanced from 131.9 ± 2.8 HV to 404 ± 1.2 HV respectively.
Plasma dissociation of monazite
Authors: Bissett H , Makhofane M M , van der Merwe R , Lotter S J 
Published: November 2019

Abstract
Monazite is a phosphate mineral which contains a significant amount of rare earth elements (REE) with thorium (Th) and a low concentration of uranium (U). The radioactive components of monazite, Th and U, make it an unattractive source of REE due to the added cost associated with radioactive waste handling. The mineral is also chemically inert requiring the use of corrosive reagents at elevated temperatures to effectively extract REEs. According to thermodynamic calculations, monazite dissociation into oxides of REE and phosphorus (P) is favourable at temperatures greater than 1000°C, while the reverse reaction occurs well below a 1000°C. Rapid cooling is required to prevent the reverse reaction. Achieving these high temperatures, with rapid heating and cooling, is possible by means of thermal plasma treatment such as a radio frequency plasma. This type of plasma system offers superior control of plasma/particle interaction, quenching rates and plasma gas composition. The objective of this study was to determine the parameters for dissociation of the monazite under various conditions to reduce its chemical inertness. Dark and grey powders were obtained under reducing conditions, while lighter powder formed in the presence of an oxygen plasma with increase particle circularity observed after plasma treatment. While SEM-EDS analysis indicated no notable change in powder composition after plasma treatment, dissolution tests proved that monazite was not only more reactive, but also more susceptible chemical reaction after treatment.
First principle study of HF molecule adsorption on TiO2 (110) surface
Authors: Tshwane D M , Modiba R , Chauke H R , Govender G , Ngoepe P E 
Published: November 2019

Abstract
Titanium and its alloy components are one of the most important technological materials, which has found extensive application in various industries. However, surface defects play a key role in the mechanical properties of these components. Currently, wet chemical etching is one of the most important procedure for surface processing due to the presence of HF since it can etch metal oxide. Therefore, there still a need to investigate the etching mechanism. In this work, adsorption of HF on TiO2(110) surface has been studied using density functional theory to investigate the fundamental process of etching. HF molecule is adsorbed on the TiO2 surface by dissociation to form Ti-F and O-H species. The interaction between HF and TiO2surface become more favorable at high HF coverage. The pre-adsorbed of water molecule is favorable for HF adsorption process, which is in good agreement with experimental results. Fluorination processes show the formation and desorption of water intermediate at 0.50 ML coverage. We also investigated the relation between the work function and Mulliken charge for HF adsorption. The results indicate that the interaction of F on the surface attracts electrons due to its higher electronegativity than oxygen. Our results suggest that adsorption of HF is considered chemisorption process.
Pillared interlayered clays as catalyst for wastewater treatment: Cost-effective and sustainable materials
Authors: Baloyi S J , Seadira T W P , Ntho T A 
Published: November 2019

Abstract
Metal oxide pillared interlayered clays (PILC) represent a novel class of materials that have attracted interests in catalytic oxidative removal of organic pollutants in wastewater. In this work, South African bentonite clay were modified by polymeric Al/Fe, Al/Zr and Al/Cr species, and the obtained pillared solids were characterized and as potential catalysts in catalytic wet air oxidation (CWAO) of phenol in aqueous solution. The placement of metal oxide pillars between bentonite clay sheets modifies their physicochemical properties (surface area and basal spacing) and catalytic activity. The Al/Zr pillared clay exhibited a higher activity compared to Al/Fe and Al/Cr for phenol oxidation. All the pillared clay catalysts allowed the total oxidation of phenol and significant removal for the total organic carbon. The metal leaching was very low in all catalysts studied.
Solar photocatalytic hydrogen production from glycerol reforming using ternary Cu/THS/Graphene
Authors: Seadira T W P , Baloyi S J , Masuku C M , Scurrell M S 
Published: November 2019

Abstract
A ternary Cu/THS/rGO photocatalyst was prepared using solvothermal method. Firstly, pure anatase T1O2 hollow spheres (THS) were prepared via hydrothermal method using titanium butoxide, ethanol, ammonium sulphate, and urea via hydrothermal method. The copper (Cu) nanoparticles were subsequently loaded on the surface of the THS by wet impregnation. During the solvothermal process, the deposition and well dispersion of Cu/THS composites onto the graphene oxide surface. Subsequently, the reduction of graphene oxide to graphene was achieved. The morphological and structural properties of the prepared samples were characterized by Scanning Electron Microscope (SEM), UV-vis DRS, and photoluminescence (PL). The activities of the prepared catalysts were tested for hydrogen production via simultaneous photocatalytic water-splitting and glycerol reforming under visible light irradiation. The excellent photocatalytic activity of the Cu/THS/rGO catalyst was attributed the rGO which acts as both storage and transferor of electrons generated at the Cu and TiO2 heterojunction, thus increasing the electro-hole pairs separation. Furthermore, the effects of reaction parameters photocatalytic hydrogen production were also studied.