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American Society for Testing and Materials

Tensile, fracture, and fatigue crack growth properties of a 3D printed maraging steel through selective laser melting

Selective laser melting of Al-Zn-Mg-Cu: Heat treatment, microstructure and mechanical properties

Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments

Progress in Metal Physics Edited by Dr. Bruce Chalmers and R. King. (Progress Series.) Vol. 5. Pp. vii + 324 + 36 plates. (London: Pergamon Press, Ltd., 1954.) 60s. net.

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Modern Physical Metallurgy

This paper reports the effects of annealing and age hardening heat treatments on the microstructural morphology and mechanical properties of 7075 Al alloy. The material was cast in the form of round cylindrical rods inside green sand mould from where some samples were rapidly cooled by early knockout and others gradually cooled to room temperature. From the samples that were gradually cooled some were annealed while others were age hardened. Both the as-cast in each category and heat treated samples were subjected to some mechanical tests and the morphology of the resulting microstructures were characterised by optical microscopy. From the results obtained there is formation of microsegregations of MgZn

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Effect of heat treatment on some mechanical properties of 7075 aluminium alloy

This research investigated the enhancement of polyethylene properties through the use of additives to make it suitable as a roofing material. To function as a roofing material, weatherability (resistance to photo-oxidation), low flammability, and good strength were identified as the key requirements that must be met by the polymer. The additives: carbon black, clay, and ammonium chloride were compounded with the polyethylene. Carbon black was used to protect against photo-oxidation; ammonium chloride was used as a flame retardant, and clay served as a flame retardant while also imparting hardness. ASTM D638-46T tensile test pieces were used to determine the strength of the mixtures, the horizontal UL 94 incipient regime flame test was used to determine flammability, and a simulated weathering test was developed to evaluate weatherability. Results indicated that at about 8.96% clay and 17.42% ammonium chloride, the polyethylene matrix has an average strength of 3.04±0.42 MPa. The horizontal UL 94 fire test showed a marked improvement of flammability properties over that observed for virgin polyethylene. The simulated weathering test also showed an improvement in weatherability properties in polyethylene containing the additives.

Development of a Roofing Material from Polyethylene through the Use of Additives

A low component count, microcontroller-based potentiostat circuit was developed through the use of operational amplifiers arranged in different feedback configurations. This was developed to alleviate the cost burden of equipment procurement in low-cost and budget applications. Simplicity was achieved in the design by the use of the microcontroller’s native functionalities and a low-cost R/2R resistor ladder digital-to-analogue converter. The potentiostat was used to investigate the Ni2+/Ni(s) redox couple in a 3-electrode cell with a silver/silver chloride reference electrode and graphite counter and working electrodes. Linear sweep voltammograms were ob-tained at scan rates of 10, 20, 30 and 40 mV/s. The analysis of the peak current versus (scan rate)1/2 plot indicated that the Ni2+/Ni(s) reduction, though conforming to the Randles-Sevcik equation, was a non-reversible redox reaction.a

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A Simplified Microcontroller Based Potentiostat for Low-Resource Applications

Some of the advantages inherent in the vacuum casting technique such as improved mechanical properties and elimination of shrinkage have been replicated in a low-cost design. Melting and vacuum requirements of the equipment were determined based on a furnace capacity of 15 kg of aluminium. Clay-based refractory and insulating bricks were used for furnace construction. The vacuum system was made from locally available materials and designed for efficiency required for vacuum casting. The equipment was used to melt and cast small-sized specimens using the lost-wax technique and compared with green sand and ceramic mould cast specimens. Tensile and shrinkage tests were carried out on all specimens. The results of the tensile tests were 123, 98 and 113 MPa for the vacuum cast, green sand cast and ceramic mould cast specimens, respectively. Furthermore, shrinkage defect which is common to both green sand and ceramic mould casting was eliminated in vacuum casting. The vacuum casting equipment cost an equivalent of about U.S $1000.00 (One thousand dollars) to construct and can be easily scaled-up for large-sized castings by increasing furnace capacity and the size of the moulding flask.

A low-cost vacuum casting equipment for aluminium alloys

Counter-gravity casting, also called vacuum casting, is a mould filling technique in which low pressure created inside a mould cavity, causes prevailing atmospheric pressure on the melt surface to bring about an upward or counter-gravity movement of the melt into the mould cavity. The process was patented in 1972 by Hitchiner Manufacturing (Lessiter & Kotzin, 2002) and different variants of the process had evolved over the years. Greanias & Mercer (1989) reported a novel valve system that could potentially increase throughput by allowing mould disengagement prior to solidification while Li et al (2007) have developed a multifunctional system aimed at aggregating different variations of the technology into a single equipment. The unique mould filling approach of the countergravity casting technique confers on it a set of unique advantages related to casting economics, defects elimination and attainment of net-shape in cast products. Such desirous attributes has ensured the growing importance of the technology, especially in power and automotive applications. A testament to the rising profile of this casting technique is its adoption in the production of a range of parts such as compressor wheels for turbo-chargers (TurboTech, 2011), automotive exhaust manifolds (Chandley, 1999) and a high-volume production (130,000 units/day) automotive engine Rocker Arm (Lessiter, 2000). The growing importance of this casting technique in some metal casting sectors notwithstanding, there is scant awareness and interest in many mainstream casting spheres. This chapter thus seeks to present a technology overview of the countergravity casting technique. The shortcomings of conventional processes are highlighted alongside the unique advantages of the countergravity technique. Challenges of the countergravity technique are also presented with discussion of efforts and prospects for their redemption.

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Bolaji Aremo

Papers

Effect of heat treatment on some mechanical properties of 7075 aluminium alloy

Development of a Roofing Material from Polyethylene through the Use of Additives

A Simplified Microcontroller Based Potentiostat for Low-Resource Applications

A low-cost vacuum casting equipment for aluminium alloys

Aluminium Countergravity Casting – Potentials and Challenges