Real-time martensitic transformation kinetics in maraging steel under high magnetic fields

Abstract

We have monitored the isothermal transformation kinetics of the austenite phase into the martensite phase in a metastable austenitic maraging steel by time-dependent magnetization measurements for temperatures from 4 to 298 K and continuous applied magnetic fields up to 30 T. The transformation kinetics is shown to be accelerated by several orders of magnitude when high magnetic fields are applied. Analyzing the transformation rate as a function of magnetic field and temperature provides direct insight into the martensite nucleation process.

In-situ determination of austenite and martensite formation in 13Cr6Ni2Mo supermartensitic stainless steel

“…Furthermore, the penetration depth in XRD analysis is limited to several microns and hence the information obtained is restricted to the surface region. Magnetic techniques have been widely used for phase-transformation measurements on different stainless steels [14][15][16]; particularly saturation magnetization measurements have been widely used for ex-situ studies [13,[17][18][19] and also sometimes for in-situ monitoring of the phase-transformation [20][21][22][23][24][25][26]. Especially in determining the austenite fraction by analyzing the saturation magnetization, the magnetic techniques are more accurate than XRD or metallography [13], as the saturation magnetization is a property, which depends on the chemical composition and the phases present in the material, but not on other microstructural features like texture or defects [27,28].…”

Anomalous kinetics of lath martensite formation in stainless steel

“…These values, which progressively increase with the degree of transformation, are consistent with literature data for isothermal martensite formation in Fe-Ni-Cr alloys and suggest that the movement of dislocations in austenite could be the rate limiting step for thermally activated martensite formation. 18,50,51 In particular, an increase in the activation energy for martensite formation during the transformation was reported in Ref. 50 and interpreted in terms of progressive hardening of the austenite phase as caused by martensite formation.…”

Real-time synchrotron X-ray diffraction study on the isothermal martensite transformation of maraging steel in high magnetic fields

“…Their remarkable properties are obtained through a process of martensite formation followed by an agehardening treatment to form fine precipitates in the martensitic matrix (Slunder et al, 1968). For some maraging steels the martensite can be formed by an isothermal phase transformation below room temperature (Holmquist et al, 1995;San Martin et al, 2010). The time-dependent formation of martensite at a constant temperature was first observed by Kurdjumov & Maksimova (1948, 1950 in an Fe-Mn alloy and has subsequently been reported for several other systems, such as Fe-Ni-Cr and Fe-Ni-Mn alloys (Kakeshita et al, 1993a;Borgenstam & Hillert, 1997).…”