Magnetic characterization of SUS316L deformed by High Pressure Torsion HONGCAI Wang 1, a , MINORU Umemoto 1, b , INNOCENT Shuro 1, c , YOSHIKAZU Todaka 1, d , HO-HUNG, Kuo 1, e 1 Department of Production Systems Engineering, Toyohashi University of Technology, Toyohashi, Aichi, 441-8580 Japan a wang@martens.me.tut.ac.jp, b umemoto@martens.me.tut.ac.jp, c innoshuro@martens.me.tut.ac.jp d todaka@martens.me.tut.ac.jp, e kuo@martens.me.tut.ac.jp Keywords: High Pressure Torsion, Vibrating Samples Magnetometer, martensite, saturation magnetization, austenite stabilization, reverse transformation. Abstract: SUS316L austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation from . The largest volume fraction of 70%  was obtained at 0.2 revolutions per minute (rpm) while was limited to 3% at 5rpm. Pre-straining of  by HPT at 5rpm decreases the volume fraction of  obtained by HPT at 0.2rpm. By HPT at 5rpm,  reverse transformation was observed for  produced by HPT at 0.2rpm. Introduction Austenitic stainless steels (ASSs) are commonly used stainless steels characterized by favorable ductility and excellent overall corrosion resistance. Its relatively low yield strength, however, hinder the application of this material. There has been a growing interest in developing ultrafine-grained steels in order to get high strength with good ductility [1]. Many studies regarding stress-induced martensite formation in ASSs have been focused on SUS 304. However, there are only few studies on the deformation-induced martensite in technologically important SUS 316L [2]. Therefore, further investigation on SUS 316L ASSs may lead to an improved understanding of this solid-state transformation. In particular, HPT is one of the techniques of Severe Plastic Deformation (SPD) and provides in comparison to other SPD methods a continuous shear deformation of the metallic material. In this study, the volume fraction of deformation induced -martensite was measured by XRD and VSM after HPT. Results show that 1) for the single strain rate: up to 70% of -martensite can be formed under low strain rate (5GPa, 0.2rpm) of HPT. However, under high strain rate (5GPa, 5rpm) the formation of martensite was limited to 3%; 2) Pre-straining of  decreased the volume fraction of -martensite and  reverse transformation was observed at 5rpm. Experimental Procedure The material used in present investigation was taken from 2 mm thick plate with the chemical composition listed in Table 1. 10 mm diameter and 0.85mm thickness disks were homogenized at 1050 o C for 1 hour and quenched in ice water to obtain a fully austenitic matrix. Then the samples were deformed by HPT at a pressure of 5GPa various at rotation speed of 0.2~5rpm. Thickness of samples is reduced from 0.85mm to about 0.6mm after HPT. Strain rate  e at the edge of samples can be derived from the von Mises equivalent strain equation  e =2RN/(3t 2 ) 0.5 , where R is distance Advanced Materials Research Vols. 239-242 (2011) pp 1300-1303 Online available since 2011/May/12 at www.scientific.net © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.239-242.1300 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 144.213.253.16-04/09/12,01:55:01)