Obrabotka Metallov. 2016 no. 1(70)

ОБРАБОТКА МЕТАЛЛОВ № 1 (70) 2016 57 МАТЕРИАЛОВЕДЕНИЕ OBRABOTKAMETALLOV (METAL WORKING AND MATERIAL SCIENCE) N 1 (70), January – March 2016, Pages 52–59 Structure and mechanical properties of the low-carbon steel after severe plastic deformation and forging Yakovleva S.P. , D.Sc. (Engineering), Professor, Head of the Material Science Department, e-mail: spyakovleva@ yandex.ru Makharova S.N. , Ph.D. (Engineering), Leading researcher, e-mail: snmachar@yandex.ru Mordovskoi P.G. , Ph.D. (Engineering), Junior researcher, e-mail: mordov@yandex.ru Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, 1 Oktyabrskaya str., Yakutsk, 677891, Russian Federation Abstract The effect of the hot forming obtained by multi-directional forging on the structure and mechanical properties of the ferrite-pearlite dual phase steel 09Mg2Si after equal channel angular pressing (ECAP) is studied. Four passes of ECAP were conducted using a route of “Bc” (90-deg rotation after each pass) adjusted to 120° internal angle of channels, 450 °С pressing temperature. Subsequent multi-directional forging (MDF) was performed with accumu- lated strain of deformation of 60 and 80%. To remove the excess of internal stress after severe plastic deformation (SPD) billets were annealed at 350 °C for 1 hour with following furnace cooling. Thermo mechanical processing by MDF affects not only the shape and structure, but, respectively, the mechanical properties of the billets too, due to the processes of deformation and recrystallization of metal. After ECAP and MDF more fine-grained structure was expected to ensure the best strength characteristics, but there was decrease in values compared to steel, which was processed only by ECAP. Nevertheless its yield point after combined processing by SPD and forging exceeds the initial values by 40-80%, the ultimate tensile strength - by 32-45%. Subsequent MDF also resulted in increase of ductility of the ultrafine grained (UFG) steel 2–3 times in comparison with steel after ECAP. After ECAP and MDF with accumulated strain of deformation 80% ferrite and pearlite grains of the steel were significantly refined to 3.8 and 2,5 μm respectively, that is 2 times less than after ECAP. Research results show the applicability of combined treatment which consists of the ECAP and MDF as manufacturing technology of work pieces with shaped form with sufficient preservation of structural and mechanical conditions obtained after ECAP. Keywords: steel, equal-channel angular pressing, multi-directional forging, nanostructuring, structure, mechanical properties. DOI: 10.17212/1994-6309-2016-1-52-59 References 1. Puertas I., Luis-Pérez C.J., Salcedo D., León J., Luri R., Fuertes J.P. Isothermal upset forging of AA5083 after severe plastic deformation by ECAE. Procedia CIRP , 2013, vol. 12, pp. 288–293. doi: 10.1016/j.procir.2013.09.050 2. Luis Pérez C.J., Salcedo Pérez D., Puertas Arbizu I. Design and mechanical property analysis of ultrafine grained gears fromAA5083 previously processed by equal channel angular pressing and isothermal forging. Materi- als & Design , 2014, vol. 63, pp. 126–135. doi: 10.1016/j.matdes.2014.05.048 3. Kim W.J., Sa Y.K., Kim H.K., Yoon U.S. Plastic forming of the equal-channel angular pressing processed 6061 aluminum alloy. Materials Science and Engineering: A , 2008, vol. 487, iss. 1–2, pp. 360–368. doi: 10.1016/j. msea.2007.10.069 4. Shi B.Q., Chen R.S., Ke W. Effects of forging processing on the texture and tensile properties of ECAEed AZ80 magnesium alloy. Materials Science and Engineering: A , 2012, vol. 546, pp. 323–327. doi: 10.1016/j. msea.2012.03.036 5. Dobatkin S.V., Rokhlin L.L., Salishchev G.A., Kopylov V.I., Serebryanyi V.N., Stepanov N.D., Tarytina I.E., Kuroshev I.S., Martynenko N.S. Struktura i svoistva magnievogo splava Mg-0,3%Ca posle mul’tiosevoi deformat-