The current study aimed at analyzing the response of semisolid A357 aluminum alloys to unconventional thermal treatment cycles of T4/T6/T7 conditions. The mechanical, electrical, and microstructural ...characterizations of such semisolid alloys were investigated. The microstructure evolutions of Fe-intermetallic phases and strengthening precipitates were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The mechanical failure of such semi solid A357 aluminum alloys, used for suspension automotive parts, is mostly related to cracking issues which start from the surface due to hardness problems and propagate due to severe load variations. For these reasons, the multiple thermal aging cycles, in this study, are applied to enhance the mechanical properties and to have compromised values compared to those obtained by standard thermal treatments. The results obtained in this work indicate that the heat treatment of this alloy can be optimized. The results showed that the optimum characteristics of A357 semisolid alloys were obtained by applying thermal under-aging cycle, interrupted thermal aging cycles and a T7/T6 two steps aging treatment condition. The electrical conductivity and electron microscopy were applied in this study to analyze the characteristics of hardening phases formed due to different aging cycles applied to the alloys investigated.
The A357-type (Al-Si-Mg) aluminum semi solid casting materials are known for their excellent strength and good ductility, which make them materials of choice, preferable in the manufacturing of ...automotive dynamic mechanical components. Semi-solid casting is considered as an effective technique for the manufacturing of automotive mechanical dynamic components of superior quality performance and efficiency. The lower control arm in an automotive suspension system is the significant mechanical dynamic component responsible for linking the wheels of the vehicle to the chassis. A new trend is to manufacture this part from A357 aluminum alloy due to its lightweight, high specific strength, and better corrosion resistance than steel. This study proposes different designs of a suspension control arm developed, concerning its strength to weight ratio. Furthermore, this study aims to investigate the effect of accelerating thermal aging treatments on the fatigue life of bending fatigue specimens manufactured from alloy A357 using the Rheocasting semi-solid technology. The results revealed that the multiple aging cycles, of WC3, indicated superior fatigue life compared to standard thermal aging cycles. On the other hand, the proposed designs of automotive suspension control components showed higher strength-to-weight ratios, better stress distribution, and lower Von-Mises stresses compared to conventional designs.
This work deals with a reliability assessment of springback problem during the sheet metal forming process. The effects of operative parameters and material properties, blank holder force and plastic ...prestrain, on springback are in- vestigated. A generic reliability approach was developed to control springback. Subsequently, the Monte Carlo simula- tion technique in conjunction with the Latin hypercube sam- pling method was adopted to study the probabilistic spring- back. Finite element method based on implicit/explicit al- gorithms was used to model the springback problem. The proposed constitutive law for sheet metal takes into account the adaptation of plastic parameters of the hardening law for each prestrain level considered. Rackwitz-Fiessler al- gorithm is used to find reliability properties from response surfaces of chosen springback geometrical parameters. The obtained results were analyzed using a multi-state limit reli- ability functions based on geometry compensations.
The thermal treatment of wood is an alternative to the chemical treatment for preservation purposes. The heat treatment process improves wood's resistance to decay and its dimensional stability. ...However, mechanical strength decreases as a result of heat treatment. Therefore, the treatment parameters have to be optimized to keep this loss at a minimum while improving other properties. Thermal treatment is new in North America, and its parameters are not yet adjusted for the Canadian species. Carrying out the parameter adjustment in an industrial furnace requires many trials which are costly in terms of material and man-power. A laboratory study was carried out to determine the effect of different parameters of the heat treatment on the mechanical properties of birch in order to optimize this process. A thermogravimetric analyzer was built to carry out the laboratory tests. The impact of the process parameters-such as maximum treatment temperature, holding time at this temperature, heating rate, and gas humidity-on the mechanical properties of birch was investigated. Temperature distributions in wood and in gas as well as the weight loss of wood were measured during the experiments. Afterwards, hardness, modulus of elasticity, modulus of rupture, and resistance to screw withdrawal of the samples were measured. The relation between the process parameters and the resulting mechanical properties was examined.
Heat treatment improves dimensional stability of wood, reduces its decay, and darkens its color. However, mechanical properties of wood can deteriorate during the heat treatment. The effect of ...heat-treatment conditions (maximum treatment temperature, heating rate, exposure time at the maximum heat-treatment temperature, and the gas humidity) on the mechanical properties of North American jack pine (
Pinus banksiana
) was studied using thermogravimetric analyzer. This type of study permits the identification of the best treatment conditions which will minimize reduction of mechanical properties of jack pine. The results showed that the degree of change in bending strength, hardness, screw withdrawal strength, and dimensional stability of jack pine during heat treatment depends strongly on the treatment conditions used. Therefore, great care should be taken to select the treatment conditions. Thermogravimetric analysis can be used as a first step for selection.
Carbon anodes are used in the electrolytic production of aluminum. The quality of anodes is directly related to the production cost, carbon and energy consumption, and environmental emissions. It is ...desired that the anodes have high density, low porosity/cracks, low electrical resistivity as well as low air and CO
2
reactivities. Low resistivity of anodes reduces energy required to produce aluminum during electrolysis. The presence of cracks and pores increases the anode electrical resistivity. Therefore, it is important to know how and when the pores and cracks form during the anode production so that the necessary actions could be taken to prevent their formation. A study was carried out to investigate the effect of different anode production parameters such as anode composition, type of raw material used, time and top-former bellow pressure of vibro-compactor, green anode cooling medium, and heating rate used during baking on the crack formation. The anodes are fabricated at the carbon laboratory of University of Quebec at Chicoutimi (UQAC) and characterized by measuring their properties (density, electrical resistivity, and surface crack density). The anode properties, hence the anode quality, were correlated with the anode production parameters. Also, their tomographic analysis was carried out to visualize and quantify the internal cracks.
Graphical abstract
The objective of this work is to understand the different mechanisms of crack formation in dense anodes used in the aluminum industry. The first approach used is based on the qualitative ...characterization of the surface cracks and the depth of these cracks. The second approach, which constitutes a quantitative characterization, is carried out by determining the distribution of the crack width along its length as well as the percentage of the surface containing cracks. A qualitative analysis of crack formation was also carried out using 3D tomography. It was observed that mixing and forming conditions have a significant effect on crack formation in green anodes. The devolatilization of pitch during baking causes the formation and propagation of cracks in baked anodes in which large particles control the direction of crack propagation.
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