An Experimental Study on Strain Rate Sensitivity of Strain‐induced Martensitic Transformation in SUS304 by Real‐time Measurement of Relative Magnetic Permeability

Abstract

With excellent mechanical properties because of strain-induced martensitic transformation (SIMT), applications of austenitic stainless steels can be extended to a further broad range of engineering fields. In order to discover applications from a clarification of their mechanical properties, especially at higher deformation rate, it is important to evaluate an amount of martensite, which can control such excellent performances of the steels during deformation. However, until now, it is quite hard to find experimental studies for the evaluation during deformation at various strain rates. In the past, volume resistivity and impedance have been measured during deformation. However, these studies have not been successful to evaluate it with a higher precision. Instead of those, it is useful to measure directly relative magnetic permeability, which has a correlation with the amount of martensite, because of focusing on a ferromagnetic characteristic of martensite. In this study, at first, SUS304, which is a kind of austenitic stainless steels, is deformed plastically under tension at various strain rates. Then, it is attempted to evaluate the amount of martensite during deformation by measuring the relative magnetic permeability expressing ferromagnetism directly. Finally, the strain and strain rate sensitivity of SIMT in the steel is discussed by obtained results.[ Ã ] T. Iwamoto

A Review on Measurement Techniques of Deformation‐Induced Transformation Kinetics in Transformation‐Induced Plasticity and Transformation‐Induced Plasticity‐Assisted Steels

“…In situ quantitative measurements based on the AC/DC magnetic permeability measurement techniques result in continuous measurement of phase fraction of austenite during deformation. [38][39][40]75] In the following sections, the basis of various techniques for quantitative assessment of austenite (as listed in Figure 1) during the deformation of TRIP/TRIP-assisted steels will be discussed. Each of these techniques is critically assessed based on their ease of use and accurate measurement of phase fraction and transformation kinetics in TRIP steels.…”

Eddy Current Detection of the Martensitic Transformation in AISI304 Induced upon Cryogenic Cutting

“…For example, Silva et al showed an exponential correlation between martensite volume fraction and phase angle [4] and Khan et al between coil impedance, impedance phase, and martensite content. [22] Compared with the method developed by Cao et al , [19] which was designed for tensile samples, it is already known in many ways that eddy current sensors can be integrated into production processes. [24,25] To be able to perform defined, production-integrated subsurface hardening, the influence of two cutting parameters, namely temperature and feed, on the DIMT was analyzed in the present study.…”

“…[ 23 ] One way to determine the DIMT behavior of steel is the nondestructive determination of the relative magnetic permeability by eliminating the influence of the jigs, which was done by Cao et al using DC voltage instead of AC voltage. [ 14,19 ] Another possibility to achieve more accurate results is to use eddy current testing as the excitation frequency can be varied and different studies demonstrate a good correlation between the martensite content and measured values in eddy current testing. For example, Silva et al showed an exponential correlation between martensite volume fraction and phase angle [ 4 ] and Khan et al between coil impedance, impedance phase, and martensite content.…”

“…For example, Silva et al showed an exponential correlation between martensite volume fraction and phase angle [ 4 ] and Khan et al between coil impedance, impedance phase, and martensite content. [ 22 ] Compared with the method developed by Cao et al , [ 19 ] which was designed for tensile samples, it is already known in many ways that eddy current sensors can be integrated into production processes. [ 24,25 ]…”

“…Nondestructive testing methods for quality control are key to ensure a defined, production-integrated martensitic subsurface hardening. Various studies [14,[17][18][19][20][21][22] have already monitored martensite formation upon plastic deformation of stainless steels with magnetic testing methods. However, most nondestructive, magnetic testing methods can lead to a misjudgment of martensite fraction due to inhomogeneous martensite distribution over the thickness.…”