1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Effect of hot extrusion parameters on microhardness and microstructure in direct recycling of aluminium chips Einfluss von Warmstrangpress-Parametern auf die Mikrohärte und das Gefüge beim Wiederverwerten von Aluminiumspänen M.H. Rady 1 , M.S. Mustapa 2 , M.A. Harimon 2 , M.R. Ibrahim 2 , S. Shamsudin 3 , M.A. Lajis 3 , A. Wagiman 3 , M.S. Msebawi 3 , F. Yusof 4 Direct hot extrusion is an alternative process for recycling aluminium without melt- ing the scrap. It utilizes low energy and is environmental friendly. This paper re- ports the microhardness and microstructure of aluminium alloy chips when sub- jected to various settings of preheating temperature and preheating time in hot extrusion process. Three values of preheating temperature are taken as 450 °C, 500 °C, and 550 °C. On the other hand, three values of preheating time were chosen (1 h, 2 h, 3 h). The influences of the process parameters (preheating tem- perature and time) are analyzed using design of experiments approach whereby full factorial design with center point analysis are adopted. The total runs are 11 and they comprise of two factors of full factorial design with 3 center points. The responses are microhardness and microstructure. The results show that micro- hardness increases with the decrease of the preheating temperature. The results also show that the preheating temperature is more important to be controlled rath- er than the preheating time in microhardness analyses. The profile extrudes at 450 °C and 1 hour has gained the optimum microhardness and it can be con- cluded that setting temperature at 550 °C for 3 hours results in the highest re- sponses for average grain sizes in analysis of microstructure. Keywords: Aluminum alloy / design of experiments / hot extrusion / microhardness / microstructure Schlüsselwörter: Aluminiumlegierung / Statistische Versuchsplanung / Warmstrangpressen / Mikrohärte / Gefüge 1 College of Engineering, University of Wasit, Hay Al Rabee, 00964 AL KUT, WASIT, REPUBLIC OF IRAQ 2 Structural Integrity and Monitoring Research Group, Universiti Tun Hussein Onn Malaysia, 86400 PARIT RAJA, BATU PAHAT, MALAYSIA 3 Sustainable Manufacturing and Recycling Techno- logy, Advanced Manufacturing and Materials Center (SMART-AMMC), Universiti Tun Hussein Onn Ma- laysia, 86400 PARIT RAJA, BATU PAHAT, MA- LAYSIA 4 University of Malaya, 50603 KUALA LUMPUR, MA- LAYSIA Corresponding author: M.H. Rady, College of Engi- neering, University of Wasit, Hay Al Rabee, 00964 AL KUT, WASIT, REPUBLIC OF IRAQ, E-Mail: mradhi@uowasit.edu.iq Materialwiss. Werkstofftech. 2019, 50, 718–723 DOI 10.1002/mawe.201800214 718 © 2019 WILEY-VCH Verlag GmbH & CO. KGaA, Weinheim www.wiley-vch.de/home/muw