Mohd Amri Lajis

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.

Electrical discharge machining (EDM) of Inconel 718 by using copper electrode at higher peak current and pulse duration

This experimental work is an attempt to investigate the performance of Copper electrode when EDM of Nickel Based Super Alloy, Inconel 718 is at higher peak current and pulse duration. Peak current, Ip and pulse duration (pulse on-time), ton are selected as the most important electrical pulse parameters. In addition, their influence on material removal rate (MRR), electrode wear rate (EWR), and surface roughness (Ra) are experimentally investigated. The ranges of 10 mm diameter of Copper electrode are used to EDM of Inconel 718. After the experiments, MRR, EWR, and Ra of the machined surfaces need to be measured in order to evaluate the performance of the EDM process. In order to obtain high MRR, higher peak current in range of 20A to 40A and pulse duration in range of 200µs to 400µs were used. Experimental results have shown that machining at a highest peak current used of 40A and the lowest pulse duration of 200μs used for the experiment yields the highest material removal rate (MRR) with value 34.94 mm 3 /min, whereas machining at a peak current of 20A and pulse duration of 400μs yields the lowest electrode wear rate (EWR) with value -0.0101 mm 3 /min. The lowest surface roughness (Ra) is 8.53 µm achieved at a lowest peak current used of 20A and pulse duration of 200μs.

Solid-state recycling of light metals: A review

This article provides an intensive review of the past and current research work on the solid-state recycling of light metals. The review includes an experimental aspect of the relevant works that clearly clarify the effects of several critical factors noted as chip preparation, reinforcing phases, die geometry, process parameter selection and performance of miscellaneous methods over the quality of the extruded profiles. Likewise, reviews of numerical and analytical works on the solid-state recycling were presented to understand the strengthening phenomena of chip-based billet through the plastic deformation. Finally, concluding remarks underline challenges of direct recycling method and subsequently highlight the potential future work on making the method as a promising alternative for sustainable manufacturing agenda.

Surface Integrity in Hot Machining of AISI D2 Hardened Steel

This study presents experimental results of machined surface integrity of die material (AISI D2 hardened steel) when hot machining (induction heating) assisted end milling using coated carbide is applied. The aim of this work was to study the influence of induction heating temperature, cutting speed, and feed on the effects induced by hard milling on surface integrity (microhardness and work-hardening). Microhardness was measured to observe the distribution of the hardness beneath the surface and to determine the effect of induction heating on the micro-hardness distribution and work-hardening phenomena. The behaviour of microhardness induced in the subsurface region when end milling under room and induction heating cutting conditions using coated carbide inserts was also investigated. The surface integrity and subsurface alteration have been investigated by employing scanning electron microscope (SEM) and Vickers microhardness tester.

A Comprehensive Study on Surface Roughness in Machining of AISI D2 Hardened Steel

Hard milling of hardened steel has wide application in mould and die industries. However, milling induced surface finish has received little attention. An experimental investigation is conducted to comprehensively characterize the surface roughness of AISI D2 hardened steel (58-62 HRC) in end milling operation using TiAlN/AlCrN multilayer coated carbide. Surface roughness (Ra) was examined at different cutting speed (v) and radial depth of cut (dr) while the measurement was taken in feed speed, Vf and cutting speed, Vc directions. The experimental results show that the milled surface is anisotropic in nature. Surface roughness values in feed speed direction do not appear to correspond to any definite pattern in relation to cutting speed, while it increases with radial depth-of-cut within the range 0.13-0.24 µm. In cutting speed direction, surface roughness value decreases in the high speed range, while it increases in the high radial depth of cut. Radial depth of cut is the most influencing parameter in surface roughness followed by cutting speed.

Optimization of Hot Press Forging Parameters in Direct Recycling of Aluminium Chip (AA 6061)

This study introduces a new approach of direct recycling using the hot press forging process that eliminates the two intermediate processes of cold-compact and pre-heating. This method leads to low energy consumption without intervening the metallurgical processes. In this study, the optimum of machined chips from high speed milling is recycled by hot press forging. The mechanical properties and surface integrity of the different chips were investigated. The performance of recycled aluminium AA 6061 chips in the mechanical and physical properties were compared with the original aluminium billet. Response surface methodology (RSM) was used to develop mathematical model of the effects on pre-compaction cycle, holding time and suitable pressure significant to the process. It is hoped that, utilization of primary metal could be fully utilized by direct recycling technique (hot press forging) introduced in this study and at the same time developing a sustainable manufacturing process technology for future needs.

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.

High Performance in EDM Machining of AISI D2 Hardened Steel

In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% - W65%) tool electrode made through PM method with a constant duty factor of 80%. In term of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were used. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The lowest surface roughness appears at the lowest material removal rate which is at a peak current of 20A and pulse duration of 600µs. The optimum machining performance can be performed by the combination of pulse duration and peak current at 600µs and 40A respectively.

Performance Evaluation of PCBN in End Milling of AISI D2 Hardened Steel under Room and Preheated Machining Conditions

In this paper, the tool life and tool wear performance of PCBN tool in end milling of AISI D2 hardened steel under room and preheated machining conditions is presented. The tool life and tool wear patterns were examined through tool maker microscope and scanning electron microscope. The results show that the dominant modes of tool wear observed were flank wear, chipping, and notch wear. The main wear mechanisms were abrasion, adhesion, and diffusion promoted by high stress and cutting temperature. It was also observed that longer tool life and higher volume metal removed could be achieved when employing higher preheating temperature.

On the Role of Processing Parameters in Producing Recycled Aluminum AA6061 Based Metal Matrix Composite (MMC-AlR) Prepared Using Hot Press Forging (HPF) Process

Solid-state recycling, which involves the direct recycling of scrap metal into bulk material using severe plastic deformation, has emerged as a potential alternative to the conventional remelting and recycling techniques. Hot press forging has been identified as a sustainable direct recycling technique that has fewer steps and maintains excellent material performance. An experimental investigation was conducted to explore the hardness and density of a recycled aluminum-based metal matrix composite by varying operating temperature and holding time. A mixture of recycled aluminum, AA6061, and aluminum oxide were simultaneously heated to 430, 480, and 530 °C and forged for 60, 90, and 120 min. We found a positive increase in microhardness and density for all composites. The hardness increased approximately 33.85%, while density improved by about 15.25% whenever the temperature or the holding time were increased. Based on qualitative analysis, the composite endures substantial plastic deformation due to the presence of hardness properties due to the aluminum oxide embedded in the aluminum matrix. These increases were significantly affected by the operating temperature; the holding time also had a subordinate role in enhancing the metal matrix composite properties. Furthermore, in an effort to curb the shortage of primary resources, this study reviewed the promising performance of secondary resources produced by using recycled aluminum and aluminum oxide as the base matrix and reinforcement constituent, respectively. This study is an outline for machining practitioners and the manufacturing industry to help increase industry sustainability with the aim of preserving the Earth for our community in the future.