VOL. 11, NO. 4, FEBRUARY 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 2258 HOT PRESS FORGING AS THE DIRECT RECYCLING TECHNIQUE OF ALUMINIUM – A REVIEW A. Ahmad, M. A. Lajis, N. K. Yusuf and A. Wagiman Sustainable Manufacturing and Recycling Technology Research Cluster, Advanced Manufacturing and Materials Center, Universiti Tun Hussein Onn Malaysia , Parit Raja, Batu Pahat, Johor, Malaysia Email: azlan357@gmail.com ABSTRACT Aluminium is totally recyclable with no downgrading of its qualities, but in the process of typical conventional aluminium recycling, there are quite a number of negative impacts. The recycling of aluminium and its alloys by direct recycling method is relatively simple, consumes small amount of energy, produce small amount of waste and does not have a harmful effect on the environment. This approach use hot press forging which eliminated two pre-process steps which typically introduce in conventional and semi-direct recycling. Hot press forging of aluminium 6xxx series is hot working process which means that the alloys should be heated around 460-520 °C, slightly above the recrystallization temperature. After heating the material, 1 to 2 hours of soaking times are sufficient to redissolve the aluminium under the flow stress less than 47 MPa. Review on recycling aluminium chips using hot press forging show that there are good potential of strength and plasticity. This is proved that such recycling technique could be employed as an alternative method to replace the conventional aluminium recycling process. Keywords: aluminium, direct recycling, hot press forging. INTRODUCTION Industrial revolution totally changed the environmental landscape for the whole world. Although the invention through the industrial revolution aims to ease the human in many aspects, but at the same time, it also disappoints the environment in tremendous elements. This disappointment had urged the authority to promulgate laws and regulation to avert global warming from the greenhouse effect. As there were saying of “The world is sick” being referred to the number pollution that had dominated the environment green and fresh surrounding. According to the report by United Nations Conference on Trade and Development (1995), Lake Batata which originally was a typical unpolluted water ecosystem has been tainted by bauxite washing activities. In over ten years, the waste from bauxite beneficiation was discharged into the lake and the effluent contains 6 – 9% of solid waste. This irresponsible doing of tailing disposal into the lake result the dynamics of the nutrients were affected, mainly in the area where tailings were discharged. Such misbehave activities should be avoided before it went far and create catastrophic toward the nature. Demand from the highly populated world nowadays is directly contributing to the tumour that had been bared by the earth. The industry is trying their best in suiting people demand and indirectly put metals and alloys to be in the top list. Aluminium demanding for various purposed for such machinery, building, packaging, electrical application, consumer durables and transport has been increasing ever since the beginning of the industrial revolution in 1760. This is due the bound of the aluminium properties which are low weight, high strength, superior malleability, easy machining, excellent corrosion resistance and good thermal and electrical conductivity. Conversely, the whole process of producing the aluminium is hugely energy-intensive. Aluminium is originally produced from bauxite. The world consumed primary aluminium for the total of 800 Mt from 1900- 2006 and it is forecasted to increase to 1200 Mt by the year 2030 (Hunt, 2007). Under those circumstances, it is crucially important to recycle secondary resources aluminium, whereby it is pecuniary advantage than processing the primary aluminium resource. Recycling aluminium only required upmost 95% less energy than to produce primary aluminium and it is also dissipate unpleasant effect toward the environment (“The International Aluminium Institute,” 2014). This review aims to prompt ideal parameters selection to produce optimal responses for mechanical and physical properties of recycled aluminium. The review covers the discussion on pre-process elimination, chip studies base on sizes, forming process by hot press forging, suitable operating temperature, flow stress and also heating time for aluminium 6xxx series. Furthermore, this review also confers about modelling and optimizing the hot press forging parameters to achieve optimum mechanical and physical responses. ALUMINIUM RECYCLING Aluminium recycling had been triggered in the early 1900’s where it aims to reduce the energy consumption and to preserve the environment. The primary aluminium production (mining bauxite from ore) required 113 gigajoule per tonne of energy but on the other hand, secondary production (conventional aluminium recycling from scrap) need only 13.6 gigajoule per tonne of energy (Rombach, 1998). Figure-1 illustrates the differentiation of energy consumption. This significant reduction of 88% of energy is contributing to the reduction of secondary aluminium price due to it lower energy consumption.