2018 - Sustainable Industrial Processing Summit & Exhibition
4-7 November 2018, Rio Othon Palace, Rio De Janeiro, Brazil
| Effect of Equal Channel Angular Pressing on Structure, Texture, and Mechanical Properties of a Magnesium Alloy Containing Rare Earth Elements Boris Straumal1; Natalia Martynenko2; Elena Lukyanova2; Georgy Raab3; Sergey Dobatkin2; Yuri Estrin4; 1INSTITUTE OF SOLID STATE PHYSICS RAS, Chernogolovka, Russian Federation; 2NATIONAL UNIVERSITY OF SCIENCE AND TECHNOLOGY MISIS, Moscow, Russian Federation; 3UGATU, Ufa, Russian Federation; 4MONASH UNIVERSITY, CENTRE FOR ADVANCED HYBRID MATERIALS, Clayton, Australia; PAPER: 309/SISAM/Regular (Oral) SCHEDULED: 12:35/Tue./Copacabana A (150/1st) ABSTRACT: Magnesium is a promising material for medical applications [1-2], owing to its good biocompatibility. Its high corrosion rate makes it suitable for bioresorbable implants, but it needs to be reduced to match the rate of healing. Addition of Rare Earth (RE) elements promotes the corrosion resistance and strength of Mg, but is usually insufficient. Therefore, the treatment of magnesium alloys by severe plastic deformation, which raises strength and sometimes also the corrosion resistance, seems promising. In this work, a magnesium alloy containing RE elements was processed by equal channel angular pressing (ECAP) in two regimes. Route Bc ECAP was carried with a step-wise decrease in temperature. In the first regime, the temperature was dropped to 350°C after 6 passes at 400°C and further 6 passes were conducted. In the second regime, the temperature was decreased from 425 to 300°C in 25°C decrements, 2 passes being carried out at each temperature. Investigation of the microstructure of the alloy showed that after the ECAP an ultrafine-grained structure with an average grain size of 1.00-0.14 μm and 0.69-0.13 μm for the first and second regimes, respectively. This is to be compared with the average grain size of 70 μm in the initial state. In addition, particles of Mg<sub>41</sub>Nd<sub>5</sub> phase with an average size of 0.41-0.18 μm and 0.45-0.18 μm were observed for these regimes. The grain refinement achieved was shown to lead to an improvement of mechanical properties. The values of the yield strength, YS=150MPa, the ultimate tensile strength, UTS=220MPa, and the tensile elongation, EL=10.5%, rose to YS=180MPa, UTS=250MPa, and EL=7% and YS=260MPa, UTS=300MPa, and EL=13.2% for the first and the second regimes, respectively. The best combination of properties for the second ECAP regime can be explained by the formation of a sharp prismatic texture, on top of a smaller grain size, as distinct from an inclined basal texture formed after the ECAP by the first regime. References: [1] S. Virtanen, Mater. Sci. Eng. B. 176 (2011) 1600-1608. [2] M. Niinomi, M. Nakai, J. Hieda, Acta Biomater. 8 (2012) 3888-3903. |
