Sains Malaysiana 48(3)(2019): 661–668

http://dx.doi.org/10.17576/jsm-2019-4803-20

Effect of Equal Channel Angular Pressing Processing Routes on Corrosion Resistance and Hardness of Heat Treated A356 Alloy

(Kesan Pemprosesan Laluan Penekanan Sudut Saluran Sama ke atas Rintangan Kakisan dan Kekuatan Haba Dirawat Aloi A356)

MOHAMED A. GEBRIL^1,2*, M. ZAIDI. OMAR¹, NK. OTHMAN³ & I.F. MOHAMED^1,4

¹Department of Mechanical and Materials Engineering, Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Department of Mechanical Engineering, Faculty of Engineering, Benghazi University, Benghazi, Libya

³School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

⁴Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

Received: 8 June 2018/Accepted: 25 December 2018

ABSTRACT

Equal channel angular pressing (ECAP) via routes A and Bc was used to process heat treated A356 alloy. The samples produced a range of microstructures in order to investigate the effect of straining on its corrosion behavior in 3.5 wt. % NaCl solution and hardness. The ECAP was conducted at room temperature in a mold with channel angle of 120°. The results show that brittle coarse silicon particles were effectively fragmented into smaller size in the Al-rich matrix after the processing. The hardness and corrosion resistance test showed improvement after T5 and T6 heat treatment, preferably to T6 due to wholly changed in silicon particles morphology than T5. The hardness increased with ECAP processing from 60.66 Hv to 1133.47, 124.91 Hv after three passes route Bc and four passes route A, respectively. The evaluation of corrosion resistance of the alloy showed improvement from 0.0424 to 0.00173, 0.00149 mmy-1 after three passes route Bc and four passes route A, respectively. In this research, both strength and corrosion resistance are improved by ECAP processing of A356 alloy using both routes.

Keywords: A356; corrosion rate; ECAP; grain size; heat treatment; microgalvanic cell

ABSTRAK

Dalam kajian ini, kaedah penekanan sudut saluran sama melalui laluan A dan Bc telah digunakan untuk memproses aloi A356 yang dirawat dengan rawatan haba. Sampel dengan pelbagai jenis mikrostruktur telah disediakan untuk mengkaji kesan terikan terhadap kekerasan dan sifat kakisan aloi A356 dalam larutan NaCl 3.5%. Kaedah ECAP dijalankan pada suhu bilik dengan menggunakan acuan yang mempunyai sudut saluran 120°. Keputusan kajian menunjukkan bahawa selepas pemprosesan, partikel silikon kasar dan rapuh bersepai menjadi partikel bersaiz kecil dalam matriks kaya Al. Ujian kekerasan dan ujian ketahanan kakisan menunjukkan bahawa sifat mekanik aloi A356 bertambah baik selepas rawatan haba T5 dan T6, terutamanya T6, disebabkan perubahan morfologi partikel silikon yang begitu ketara. Kekerasan aloi A356 masing-masing meningkat daripada 60.66 Hv kepada1133.47 Hv dan 124.91 Hv selepas pemprosesan ECAP melalui laluan Bc tiga kali dan laluan A empat kali. Keputusan penilaian menunjukkan bahawa ketahanan kakisan aloi masing-masing meningkat daripada 0.0424 kepada 0.00173 dan 0.00149 mmy-1 selepas pemprosesan ECAP melalui laluan Bc tiga kali dan laluan A empat kali. Oleh itu, dapat disimpulkan bahawa kekuatan dan ketahanan kakisan aloi A356 meningkat dengan menggunakan kaedah pemprosesan ECAP melalui kedua-dua laluan.

Kata kunci: A356; ECAP; kadar kakisan; rawatan haba; saiz butiran; sel mikrogalvanik

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*Corresponding author; email: gebril.ukm@gmail.com