A comparison of microstructure evolution and mechanical behavior of a F138 austenitic stainless steel after severe plastic deformation at room temperature and at 300oC

A.M. KLIAUGA; V. L . SORDI; R. E. BOLMARO; M. FERRANTE

Conferencia; ICSMA 16; 2012

ICSMA

The deformation mechanism of low stacking fault fcc alloys depends on deformation rate and temperature. At low temperature, high deformation rates deformation twinning is active whereas at higher temperatures and lower deformation rates dislocation density is predominant [1]. The nanoscale deformation twins in low-SFE materials play an important role in the grain refinement process [2,3]. In this work A F138 austenitic stainless steel, which is a low  carbon, low vacuum remelted  stainless steel from the family or the AISI 316 alloys, and used for chirurgical implants, was deformed by ECAP (up to 4 passes following route A in a die with internal angle of 120o) at room temperature and at 300oC. The microstructural evolution was followed by TEM, EBSD and x ray diffraction. Work hardening behavior was studied by making use of Kocks-Mecking plots and hardness measurements.  At room temperature the main deformation mechanism was mechanical twinning whereas at 300oC discordance gliding was predominant; therefore, grain subdivision was dominated by the fragmentation of deformation twins inside deformation bands at room temperature and by subgrain formation at 300oC. At either temperature no martensite formation was detected. Higher hardness increment was obtained by deformation at room temperature and ECAP 300oC gives the best strength-ductility combination. [1].  Y. Zhang, N.R. Tao , K. Lu Acta Materialia 59 (2011) 6048 [2].  S. Scheriau, Z. Zhang, S. Kleber, R. Pippan Mat Sci Eng A 528 (2011) 2776 [3].  Y.T. Zhu,J. Narayan, J.P.Hirth ,S.Mahajan, X.L.Wud, X.Z Liao Acta Materialia 57 (2009) 3763