59 research outputs found

    Hot press as a sustainable direct recycling technique of aluminium: mechanical properties and surface integrity

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    Meltless recycling technique has been utilized to overcome the lack of primary resources, focusing on reducing the usage of energy and materials. Hot press was proposed as a novel direct recycling technique which results in astoundingly low energy usage in contrast with conventional recycling. The aim of this study is to prove the technical feasibility of this approach by characterizing the recycled samples. For this purpose, AA6061 aluminium chips were recycled by utilizing hot press process under various operating temperature (Ts = 430, 480, and 530 °C) and holding times (ts = 60, 90, and 120 min). The maximum mechanical properties of recycled chip are Ultimate tensile strength (UTS) = 266.78 MPa, Elongation to failure (ETF) = 16.129%, while, for surface integrity of the chips, the calculated microhardness is 81.744 HV, exhibited at Ts = 530 °C and ts = 120 min. It is comparable to theoretical AA6061 T4-temper where maximum UTS and microhardness is increased up to 9.27% and 20.48%, respectively. As the desired mechanical properties of forgings can only be obtained by means of a final heat treatment, T5-temper, aging after forging process was employed. Heat treated recycled billet AA6061 (T5-temper) are considered comparable with as-received AA6061 T6, where the value of microhardness (98.649 HV) at 175 °C and 120 min of aging condition was revealed to be greater than 3.18%. Although it is quite early to put a base mainly on the observations in experimental settings, the potential for significant improvement offered by the direct recycling methods for production aluminium scrap can be clearly demonstrated. This overtures perspectives for industrial development of solid state recycling processes as environmentally benign alternatives of current melting based practices

    Development of surface roughness models in end milling titanium alloy Ti-6Al-4V using uncoated tungsten carbide inserts

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    This paper focuses on developing an effective methodology to determine the performance of uncoated WC-Co inserts in predicting minimum surface roughness in end milling of titanium alloys Ti-6Al-4V under dry conditions. Central composite design of response surface methodology is employed to create an efficient analytical model for surface roughness in terms of cutting parameters: cutting speed, axial depth of cut, and feed per tooth. Surface roughness values were measured using a surface roughness measuring instrument- Mitutoyo Surftest model SV-500. Design of expert package was applied to establish the first order and the second order model and develop the contours. The adequacy of the predictive model was verified using analysis of variance

    Improved tool life in end milling Ti-6Al-4V through workpiece preheating

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    This paper presents the investigation of tool life improvement in end-milling of Titanium Alloy Ti-6Al-4V through workpiece preheating. End milling tests were conducted on Vertical Machining Centre with full immersion cutting. Induction heating was utilized during end milling for preheating. The titanium alloy Ti-6Al-4V bar was used as the workpiece. Machining was performed with a 20 mm diameter end-mill tool holder fitted with one PCD inserts. All of the experiments were run under room temperature and preheating condition at 315, 450, and 650ºC. Flank wear has been considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker’s microscope. Tests were conducted until an insert was rejected when an average flank wear greater than 0.30 mm was recorded. Cutting force and torque measurements were conducted using the Kistler Rotating Cutting Force Dynamometer. Vibration during cutting was captured using an online vibration monitoring system. Scanning electron microscope (SEM) was also used to investigate the wear morphology. The results led to conclusions that workpiece preheating significantly increases the tool life of PCD inserts in end-milling of Titanium Alloy Ti-6Al-4V

    Powder Mixed Dielectric in Electrical Discharge Machining of Inconel 718 / Said Ahmad...[et al.]

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    Inconel 718 is one of the most difficult to cut material due to its, high hardness, high toughness, and poor thermal conductivity results in heat concentrated in the cutting zone, making it ineffective to be processed through conventional machining. So usually, an electrical discharge machining (EDM) is chosen in order to overcome such limitations. However, EDM is known as a slow machining process. Thus, by employing powder mixed in the dielectric fluid it is believe to enhance the machining efficiency. To achieve high performance in EDM for this research, higher peak current, Ip up to 40A, pulse duration, ton up to 400μs and powder concentration, Cp up to 4g/l were selected as the main parameters. Copper tungsten (CuW) was used as an electrode. The circulating dielectric system called High Performance EDM (HPEDM) was applied to conduct the experiment involving powder mixed dielectric. Their influence on the machinabilities of the material removal rate (MRR), and electrode wear rate (EWR), were experimentally investigated. The surface topography of the machined work piece and surface morphology of the electrode also have been observed. The results have shown that, at a highest Ip=40A and the lowest ton=200μs with Cp=4g/l yields the highest MRR. The improvement is almost 50% when comparing without powder concentration at the same parameter settings. In the case of EWR, lowest value of EWR was obtained at Ip=20A, ton=400μs and Cp=0g/l

    Improved tool life in end milling Ti-6A1-4V through workpiece preheating

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    This paper presents the investigation of tool life improvement in end-milling of Titanium Alloy Ti-6Al-4V through workpiece preheating. End milling tests were conducted on Vertical Machining Centre with full immersion cutting. Induction heating was utilized during end milling for preheating. The titanium alloy Ti-6Al-4V bar was used as the workpiece. Machining was performed with a 20 mm diameter end-mill tool holder fitted with one PCD inserts. All of the experiments were run under room temperature and preheating condition at 315, 450, and 650ºC. Flank wear has been considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker’s microscope. Tests were conducted until an insert was rejected when an average flank wear greater than 0.30 mm was recorded. Cutting force and torque measurements were conducted using the Kistler Rotating Cutting Force Dynamometer. Vibration during cutting was captured using an online vibration monitoring system. Scanning electron microscope (SEM) was also used to investigate the wear morphology. The results led to conclusions that workpiece preheating significantly increases the tool life of PCD inserts in end-milling of Titanium Alloy Ti-6Al-4V

    Characterization of Anisotropic Damage Behaviour of Recycled Aluminium Alloys AA6061 Undergoing High Velocity Impact

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    It is impossible to ignore the realm of the topics related recycling aluminium scraps. The recycled form of this material can be a good replacement for the primary resources due to the economic and environmental benefits. Numerous investigation must be conducted to establish the mechanical behaviour before the specific applications can be identified. In this research, Taylor Cylinder Impact tests used to investigate anisotropic damage behaviour in recycled aluminium alloy is presented. To be specific, by performing Taylor Cylinder Impact test at velocities ranging from 190m/s to 300m/s, anisotropic and damage characteristics can be observed in the samples as a function of the large stress, strain, and strain-rate gradient. The application of Taylor Cylinder Impact test as a technique to validate both the constitutive and dynamic fracture responses in such materials is also discussed. The structure of recycled aluminium AA6061 including the damage initiation and evolution are observed under optical microscope (OM) and scanning electron microscope (SEM). The results revealed that the damage evolution of the material change with the increasing impact velocity. Further, the digitised footprint analysis showed a pronounced anisotropic characteristic of the recycled aluminium AA6061

    Preliminary studies on hydrothermal synthesis of zeolite from Malaysian kaolinite clays

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    The use of kaolin as a source of silica and alumina for synthesis of zeolite has been widely reported with various compositions and processing routes. However, since kaolin is highly influenced by geological origin and geographical formation, coupled with the processing method, two different crude kaolin were obtained at various locations in Peninsular Malaysia to serve as precursor for synthesis of zeolite. Hydrothermal treatments were made at reasonable low temperature of 90°C in an oven. The synthesized product was then analyzed using X-ray diffraction and scanning electron microscopy, to evaluate the potentials of the process and the product. The outcome of the analysis suggested that the breaking down of the clay structure and the armophization process can improve raw material reactivity. However, the crystallinity and composition of the crude kaolin together with appropriate incubation time can greatly influence the synthesis process and the product

    Modelling and optimization of Chromium Powder Mixed EDM Parameter Effect Over the Surface Characteristics by Response Surface Methodology Approach

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    In this paper, an optimization of chromium powder mixed parameters effect, i.e. discharge current, pulse on time and Cr powder concentration of AISI D2 steels in Powder Mixed EDM (PMEDM) has been made. RSM has been employed to plan and analyzed the experiment. Central composite design (CCD) was chosen as the RSM design that is useful for investigating the quadratic effects. The version 8.0 of the Design Expert software was used to develop the experimental plan for RSM. A mathematical model in the form of the multiple regression equation for second order response surface with the best fittings was developed. The results identify that discharge current and pulse on time the most important parameters effect to minimize recast layer. With the topmost desirability solution, the suggested optimum parameter of discharge current is 20.12 A, pulse-on time 50.14 µs and 3.96 g/L powder concentration to minimize recast layer

    Effect of the Heat treatment on Mechanical and Physical Properties of Direct Recycled Aluminium Alloy (AA6061)

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    Products by solid-state recycling of aluminum chips in hot extrusion process were controlled by temperature related parameters using preheating temperature 450 °C, 500 °C, and 550°C for 1 hr, 2 hr, and 3 hr preheating time. By using Design of Experiments (DOE), the results found that the preheating temperature is more important to be controlled rather than the preheating time in analysis both mechanical and physical properties. The results also found that increasing of temperature led to the high tensile strength and low microhardness. The profile extruded at 550 °C with 3 hr duration had gained the optimum case to get the maximum tensile strength and the profile extruded at 450 °C with 1 hr had result the optimum case to gain the maximum microhardness. For the optimum cases, heat treatment was carried out using quenching temperature at 530 ºC for 2 hr and aging process at 175 ºC for 4 hr. The tensile strength and microhardness of extrudes specimens were improved significantly by heat treatment
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