Effect of process parameters on tensile strength and morphology of friction stir spot welds of aluminium and copper

Abstract: Friction stir spot welding (FSSW) is a solid-state welding process used for joining similar and dissimilar materials. AA1060 and C11000 sheets were joined using different process parameters and tool geometries. The presence of a copper rings also called hooks were observed in all the produced spot welds and their length increases with the tool shoulder plunge depth; whereas the spot welds produced at 1200 rpm for the two tool geometries exhibited a decrease and a slight increment in the length of the copper ring using a flat pin/flat shoulder and conical pin/ concave shoulder, respectively. Furthermore, the mapping of the produced spot weld using energy dispersive spectroscopy (EDS) exhibited different microstructures with the presence of copper fragments and particles in the aluminium matrix. It was also observed that, the shoulder plunge depth had an effect on the shear tensile results, except for the weld produced at 800 rpm when using a conical pin and a concave shoulder

Microstructure and electrical resistivity properties of copper and aluminium friction stir spot welds

Abstract: Dissimilar metal joining methods are essential for the manufacturing of a various structures and parts in the industries. Friction stir spot welding process was performed on 3 mm thick AA1060 and C11000. This paper presents the results on the microstructure, chemical analysis and electrical resistivities of the produced joints. The microstructure showed a contrast between the two different materials namely copper and aluminium and the presence of a copper ring (hook) in all the produced spot welds. The presence of copper particles in the aluminium matrix was observed in most of the welds. The conducted energy dispersive spectroscopy (EDS) analysis confirmed the presence intermetallic compounds. It was observed that, the spot weld produced using 800 rpm and 1 mm shoulder plunge depth exhibited a low electrical resistivity value of 0.009 μΩ, which shows an appreciation of 0.011 μΩ (55 %), compared to the average of the parent materials (0.020 μΩ). This could be an attractive option for electrical applications

Effect of milling parameters on microhardness and microstructure during dry and flood milling of Ti-6Al-4V

Abstract: The current study focuses on investigating the effect of milling parameters on the microhardness during dry and flood milling of Ti-6Al-4V. Dry and flood milling were performed while varying spindle speed (120, 150, and 180 rev/min), depth of cut (1, 1.5 and 2 mm), as the feed rate (4.6 mm/min) was kept constant. Subsequent to milling, milled surfaces microhardness were measured and microstructure evolution was analysed using an optical microscope. It was established that the deformation of beta phase increased with increase of spindle speed during dry milling while during flood milling there was no microstructural change associated to the increase of the spindle speed. On the other hand, the hardness increased as result of increase of spindle speed during both dry and flood milling. Flood milling generated a maximum hardness of 338.44 HV at 180 rev/min which is superior to maximum hardness of 336.36 HV produced during dry milling. Dry milling at 1.5 mm depth of cut generated maximum deformation of beta phase while during flood milling maximum deformation was recorded at 2 mm depth of cut. The hardness increased with increment of depth of cut during flood milling while it decreased with increase of depth of cut during dry milling

Characterisation of the evolving properties of friction stir spot aluminium and copper welds

Abstract: Dissimilar metal joining techniques are necessary for the manufacturing of a number of structures and parts in the industries. Aluminium and copper are widely used in engineering structures, due to their unique performances, such as higher electrical conductivity, heat conductivity, corrosion resistance and mechanical properties even if they have considerable differences in their melting points. Among the aims for future years in the automotive industry is the development and implementation of new technologies, including a broad application of friction stir spot welding (FSSW) of similar and dissimilar materials. Friction stir spot welding (FSSW) is a variant of friction stir welding (FSW) for spot welding applications. Joining aluminium and copper to meet the requirements from the electrical industry have been conducted by using different joining techniques, such as ultrasonic welding, friction welding and laser welding. However, the major challenge with these techniques is the occurrence of brittle intermetallic compounds in the joint zone. FSSW has been successfully used to join aluminium and copper by a few researchers; but more research is needed to investigate the evolving properties of FSSW between copper and aluminium. The current research project joined 3 mm thick AA1060 and C11000, by using friction stir spot welding (FSSW), and by using different tool geometries namely a flat pin/flat shoulder and a conical pin/concave shoulder and different process parameters, in order to fill the gap in the literature in this field of study. Limited research results exist on friction stir spot welding between aluminium and copper. However, the successful joining of these two materials has the potential for many applications in the industry. The spot welds were produced and characterised through optical microscopy, and by scanning electron microscopy for the microstructural evolution; while the chemical and phase identification were analysed using energy dispersive spectroscopy and X-ray diffraction, respectively. Furthermore, tensile testing, microhardness profiling, residual stress analysis, electrical resistivity and statistical analysis were also conducted. This was done to investigate the relationship between the process parameters, the tool geometry and the produced welds. The real time forces acting during the welding process were monitored and analysed. It was observed that the maximum forge...D.Phil. (Mechanical Engineering Science

Characterization of QwaQwa sandstones and design of solar powered microwave cutter equipment for artisanal mining

M.Tech.Artisanal mine of sandstones especially in rural area are facing numerous challenges including the use of inadequate tools for the processing of sandstones. Since the current processing technique has limitations which consist of the use of hammer and chisels, there is a need to develop environmentally friendly and cost effective techniques for the processing of sandstones. In this project, six different sandstones samples (yellowish, blackish, reddish, greenish, greyish and whitish) from QwaQwa rural area were collected and characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and an optical microscope. In addition, physical properties of sandstones were also carried out including compressive strength, dielectric properties and water absorption. Furthermore sandstones samples were irradiated using multi- and single- mode microwave cavities to investigate the effect on the mineralogy of sandstones. The analysis of mineralogical change was carried out using XRD. Additionally a microwave multimode cavity was used to investigate the weight loss of sandstones after being irradiated. A microwave cavity was designed based on the characteristics of sandstones and it was simulated. A photovoltaic solar system was sized to power the microwave cutter. The experimental work was carried out on a laboratory scale. The XRD analysis revealed that quartz was the major mineral present in all sandstones which confirms that QwaQwa sandstones are quartz based sandstones. Feldspar minerals such as illite and albite were also found. Additional minerals were identified at trace level including glauconite, kaolonite, crysobalite and orthoclase. On the other hand, the XRD results of the irradiated samples using a single- and multi- mode cavity for 60 seconds revealed a strong presence of quartz which means no significant changes were observed. However, some minor overlapped peaks suspected to be muscovite (KAl2(Si3Al)O10(OH,F)2) in three samples (blackish, greyish and yellowish) were noticed. XRF study showed that the chemical elements available in the six sandstones samples are: aluminium, calcium, iron, potassium, magnesium, manganese, sodium, phosphorus, silicon and titanium

Effect of laser power and scanning speed on the characteristics of laser metal deposition of Ti6Al4V + W composite powder on Ti6Al4V substrate

The usage of different powders to enhance the surface properties of base materials has an impact on the cost. Laser Metal Deposition (LMD) of Ti6Al4V + W composite was used and the effect of laser power and scanning speed was investigated. The microstructure, microhardness, and x-ray diffraction analyses, and wear tests were conducted. The microstructure of the samples fabricated using higher laser power (1400W) displayed larger grains when compared to the ones fabricated using lower laser power (800 W). The Full Width at Half Maximum (FWHM) values showed some changes with the variation of scanning speeds. Furthermore, the x-ray diffraction patterns did not show the formation of new phases. A similar trend on the microhardness profiles for all the fabricated samples was observed. Higher microhardness values were observed in the top part of the deposited material. The microhardness profile showed similar trends for all the analysed samples. Higher microhardness values were measured at the top of deposition and decreased progressively. On the other hand, the scanning speed did not affect the wear volume, though the highest wear volume of 0.144 mm was observed for the sample fabricated using 800 W laser power and 0.7 m min ^−1 . This shows that process parameters such as laser power and scanning have an impact on the resulting properties of deposited composite material

Vallée du Ntem (sud Cameroun)

International audienceThis chapter is devoted to the Ntem Valley in South Cameroon, one of the multidisciplinary study areas for more than 5 years (1994/2000) of the European APFT program "Avenir des Peuples des Fprêts tropicales" (Future of Rainforest Peoples - FRP). ). It presents the geographical location, the demographic dimensions of the population of this region (fertility, mortality, child mortality in particular), the social and cultural aspects (ethnic groups, ethnolinguistics, ethnomusicology, education, religions, social organization and its fundamental aspects, those related to the kinship system and the politico-legal system. It also addresses questions of rural / urban population mobility and in particular relations with the city. The socio-health context with health indicators and the use of traditional medicine and the therapeutic routes of the population The activities and strategies of subsistence (breeding, fishing, hunting, trapping, collecting etc ...) and what they produce in terms of impact on the environment through the evolution of surfaces cultivated, forest and biodiversity regeneration or the impact on flora and fauna.The chapter allows the various researchers to make a number of recommendations for the future of the peoples of this forest region.See also the book, "Man and the Tropical Forest", edited by Bahuchet, Bley, Pagezy, Vernazza-Licht www.ecologie-humaine.euCe chapitre est consacré à la Vallée Ntem au Sud Cameroun, l'un des terrains d'étude multidisciplinaire pendant plus de 5 ans (1994/2000) du programme européen APFT "Avenir des Peuples des Fprêts tropicales" (Future of Rainforest Peoples - FRP). Il présente la situation géographique, les dimensions démographiques de la population de cette région (fécondité, mortalité, mortalité des enfants notamment), les aspects sociaux et culturels (ethnies, ethnolinguistique, ethnomusicologie, scolarisation, religions, organisation sociale et ses aspects fonciers, ceux liés au système de parenté et au système politico-juridique. Il aborde egalement les questions de mobilité de population rural/urbain et notamment les relations avec la ville. Le contexte socio-sanitaire avec les indicateurs de santé et le recours à la médecine traditionnelle et aux itinéraires thérapeutiques de la population. Les activités et les stratégies de subsistance (elevage, pêche, chasse, piégeage, collecte etc...) et ce qu'elles produisent en terme d'impact sur le milieu à travers l'évolution des surfaces cultivées, la régénération de la forêt et de la biodiversité ou l'impact sur la faune et la flore.Le chapitre permet aux différents chercheurs de faire un certain nombre de recommandations pour l'avenir des peuples de cette région de forêt.Voir egalement l'ouvrage L'homme et la Forêt tropicale, sous la direction de Bahuchet, Bley, Pagezy, Vernazza-Licht www.ecologie-humaine.e

Vallée du Ntem (sud Cameroun)

International audienceThis chapter is devoted to the Ntem Valley in South Cameroon, one of the multidisciplinary study areas for more than 5 years (1994/2000) of the European APFT program "Avenir des Peuples des Fprêts tropicales" (Future of Rainforest Peoples - FRP). ). It presents the geographical location, the demographic dimensions of the population of this region (fertility, mortality, child mortality in particular), the social and cultural aspects (ethnic groups, ethnolinguistics, ethnomusicology, education, religions, social organization and its fundamental aspects, those related to the kinship system and the politico-legal system. It also addresses questions of rural / urban population mobility and in particular relations with the city. The socio-health context with health indicators and the use of traditional medicine and the therapeutic routes of the population The activities and strategies of subsistence (breeding, fishing, hunting, trapping, collecting etc ...) and what they produce in terms of impact on the environment through the evolution of surfaces cultivated, forest and biodiversity regeneration or the impact on flora and fauna.The chapter allows the various researchers to make a number of recommendations for the future of the peoples of this forest region.See also the book, "Man and the Tropical Forest", edited by Bahuchet, Bley, Pagezy, Vernazza-Licht www.ecologie-humaine.euCe chapitre est consacré à la Vallée Ntem au Sud Cameroun, l'un des terrains d'étude multidisciplinaire pendant plus de 5 ans (1994/2000) du programme européen APFT "Avenir des Peuples des Fprêts tropicales" (Future of Rainforest Peoples - FRP). Il présente la situation géographique, les dimensions démographiques de la population de cette région (fécondité, mortalité, mortalité des enfants notamment), les aspects sociaux et culturels (ethnies, ethnolinguistique, ethnomusicologie, scolarisation, religions, organisation sociale et ses aspects fonciers, ceux liés au système de parenté et au système politico-juridique. Il aborde egalement les questions de mobilité de population rural/urbain et notamment les relations avec la ville. Le contexte socio-sanitaire avec les indicateurs de santé et le recours à la médecine traditionnelle et aux itinéraires thérapeutiques de la population. Les activités et les stratégies de subsistance (elevage, pêche, chasse, piégeage, collecte etc...) et ce qu'elles produisent en terme d'impact sur le milieu à travers l'évolution des surfaces cultivées, la régénération de la forêt et de la biodiversité ou l'impact sur la faune et la flore.Le chapitre permet aux différents chercheurs de faire un certain nombre de recommandations pour l'avenir des peuples de cette région de forêt.Voir egalement l'ouvrage L'homme et la Forêt tropicale, sous la direction de Bahuchet, Bley, Pagezy, Vernazza-Licht www.ecologie-humaine.e