Effect of operating temperature on direct recycling aluminium chips (AA6061) in hot press forging process

A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430˚C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520˚C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process

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

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

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

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.]

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

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

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

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

Surface Roughness and Surface Topography of Inconel 718 in Powder Mixed Dielectric Electrical Discharge Machining (PMEDM)

In high speed EDM, maximum material removal rate (MRR) is a desirable to increase productivity rate and reducing production cost to the need of industry. However, the surface finish of the machined surface also cannot be neglected since it related to product quality and safety factor especially when to cut difficult to machine material such Inconel 718, which is widely used in aerospace industry. Surface roughness as one of the surface integrity criteria was choose as a response in this research. High discharge current from 20A to 40A, longer pulse on-time (pulse duration) from 200µs to 400µs and the different concentration of the nano Alumina powder were selected as the main parameters, respectively. The effect of powder mixed dielectric in EDM performance in terms of surface roughness was evaluated. The dielectric circulating system known as High Performance Electrical Discharge Machine (HPEDM) was attached to the conventional EDM machine to run the experiments involving powder mixed dielectric. The experiment results shows that, the highest peak current deteriorated the surface roughness. The surface roughness, Ra was increased with the increasing of the peak current. The result also shows that an increasing of the pulse duration the surface roughness was slightly improved. It is observed that, the value of Ra was closely related to the surface topography characteristic of the machined surfaces and directly depends on the applied discharge energy. There is no improvement in surface roughness when powder additive was mixed in a dielectric fluid