Magnetic properties of thermal-aged 316 stainless steel and its precipitated phases (original) (raw)
Related papers
Materials Science and Engineering: A, 2007
All duplex stainless steel samples used for experimental work must be solution treated before any subsequent tests are performed on them. In this work, the effects of solution treatment parameters (temperature and soaking duration) and plastic deformation on the ageing behaviour and ac magnetic susceptibility of two duplex stainless steels, which differ in composition, morphology and ferrite content, have been investigated. Effects of different pre-treatments on the morphology, composition and stability of the ferrite phase have been studied, too. The use of ac magnetic susceptibility for the measurement of ferrite content is feasible, but the effect of plastic deformation must be properly accounted for, or else the ferrite content may be underestimated. The ac susceptibility is dependent upon the composition of the ferrite phase. Dissolution of the ferrite in the range of 650-800 • C obeys the Johnson-Mehl-Avrami equation. Raising the solution treatment temperature may increase the activation energy for transformation. For samples used in most experimental work, performing a very long solution treatment may not be necessary.
Magnetic properties of the UNS S39205 duplex stainless steel
Journal of Alloys and Compounds, 2003
Duplex stainless steels (DSS) present a fine microstructure of paramagnetic austenite and ferromagnetic ferrite. In this work the microstructures of UNS S39205 (old S31803) duplex stainless steel (DSS) samples were modified by high temperature treatment at 1300 8C in vacuum followed by four different cooling rates and thermal aging at 475 8C for three different times. Magnetic properties (saturation magnetization, remanence, coercive force and magnetic transition temperature) are reported. A relationship between the magnetic saturation and the ferrite volume fraction (C ) was proposed. An increase in the Curie temperature (T ) was observed during the a c aging at 475 8C in the fast cooled samples, but not in the slowly cooled ones, where the C was too low.
Tempering behavior in the temperature range 150-500 °C of a Fe-15Cr-1Mo-0.3C-0.38N (mass-%) martensitic-austenitic stainless steel, commercially known as Cronidur ® 30, was studied by means of dilatometry, magnetic saturation, and hardness measurements. The first stage of tempering, centered around 150 °C, was characterized by an increase in the hardness and magnetic flux density. In the second stage of tempering centered around 350 °C, the hardness continuously decreased. Magnetic saturation studies indicated an initial decrease in the magnetic flux density which changed to an increase in the upper temperature range for the second stage. The occurrence of secondary hardening was the main characteristic of the third stage of tempering and it is thought to mark the end of precipitation reactions under paraequilibrium conditions.
Magnetic Evaluation of Water-Quenched Modified 9Cr1Mo Steel Subjected to High Temperature Aging
The present work adresses the evaluation of modified 9Cr-1Mo steels magneic hystersis loop and magnetic Barkhsuen emission techniques for the samples subjected to high temperature ageing for different durations. The initially quenched and then tempered material revealed different magnetic behaiour with ageing. The relxation of stresses and reduction of high value of dislocations due to quenching in the initial perriod of ageing was observed with lowering of coercivity and an increase in MBE signal. Further ageing above 150 hours led to fine distribution of carbides in the matrix which led to the subsequent magnetic hardening. The formaiton of the fine carbides was also observed from Scanning electron micrographs. At higher ageing periods beyond 500 hours, the carbides migrated towards the grain boundary leading to loweing in the density of the fine carbides in the matrix and a consequent magnetic softening due to easy domain wall propagation.
Magnetic testing of ferritic stainless steel
APPLIED PHYSICS OF CONDENSED MATTER (APCOM 2021)
Structural changes due to annealing were analyzed on ferritic stainless steel Electrodur EN 1.4105 (AISI 430F) specimens. Changes of magnetic properties and selected parameters of Barkhausen noise were compared to microstructural changes detected by microscopy and Vickers hardness measurement.
Magnetic response of Cu (25wt.%)-316 grade stainless steel processed by ball milling
Journal of Non-Crystalline Solids, 2012
Powder blend comprising Cu (25 wt.%) and 316-stainless steel (75 wt.%) has been subjected to ball milling upto 70 h followed by isothermal annealing at the temperature range of 350-750°C for 1 h to investigate the evolution of microstructure and magnetic properties. The ball milling of the powder blends after 10 h has resulted in partitioning of the austenite stabilizing elements such as Ni from 316-stainless steel to elemental Cu leading to the transformation of the Bravais lattice of the Fe-rich phase from fcc (γ) to bcc (α). During further ball milling of the powder mixture upto 20 h, the α-Fe has dissolved completely in Cu, leading to the formation of partial amorphous phase after 70 h of milling. The amorphous phase of the alloy has been found to stable after annealing at 350°C and super paramagnetic in nature. Annealing of the alloy at higher temperatures has resulted in precipitation of nanocrystalline bcc-Fe in the Cu evolving ferromagnetic properties. Annealing at 750°C has resulted in collapse of the hysteresis loop due to the diminished exchange interaction as the result of grain coarsening of the α-Fe and Cu.
Decomposition of the Ferritic Phase in Isothermally Aged SAF 2507 Duplex Stainless Steel
Materials Science Forum, 2008
Duplex stainless steels constitute a famous group of the stainless steels. They consist of mainly ferritic and austenitic phases. The ratio between these phases is regulated by numerous alloying elements and low content of carbon. Because of this strong alloying a lot of metallurgical processes can take place at high temperature, e.g. the decomposition of ferritic phase into σ-phase and secondary austenite. In this paper the changes of amounts of these three phases are studied by automated EBSD, saturation magnetization measurement, XRD-analysis and micro-hardness test. Similar results were obtained by the different applied measurements for the change of phase ratios due to the isothermal heat treatment.
Magnetic properties evaluation of ageing behaviour in water-quenched 5Cr–0.5Mo steel
Journal of Physics D: Applied Physics, 2009
Magnetic Barkhausen emissions and magnetic hysteresis measurements were carried out on water-quenched 5Cr-0.5Mo steel subjected to ageing at 600 • C up to 5000 h. During initial ageing, this steel exhibited magnetic softening, which was attributed to relaxation of quenching stress in the material as well as decrease in dislocation density and migration of interstitial carbon atoms towards the grain boundary. Further ageing resulted in magnetic hardening owing to the restricted movement of the domain wall by the precipitation of carbides such as M 3 C 2 , M 2 C, M 7 C 3 where M stands for Fe, Cr or a combination of them. At longer ageing periods, magnetic behaviour was affected by a change in the composition and morphology of the carbides. Massive M 23 C 6 types of carbides were formed during longer periods of ageing. The coarsening of carbides decreased the pinning density for the domain wall motion and affected the magnetic properties of the steel. The effect of demagnetizing field from voids and non-magnetic massive carbides also affected the magnetic behaviour. Magnetic behaviour and Vickers hardness measurements during ageing have been effectively supported by microstructural evaluations suggesting the capability of the magnetic techniques for assessment of damage during ageing in high temperature 5Cr-0.5Mo steel components.
Magnetic properties of an AISI 420 martensitic stainless steel
Journal of Alloys and Compounds, 2000
The magnetic properties (coercive force, saturation and residual magnetization, and Curie temperature) of an AISI 420 steel were measured for different heat treatment conditions (quenching and tempering). The results show that the material is magnetically softer in the annealed condition and after oil quenching an increase of coercive force ( H ) and residual induction (B ) and a decrease of saturation M c r magnetization (s ) are observed. Tempering in the 300-5008C range promotes a further increase of H and B values. Tempering in the s M c r 500-6508C range promotes an increase of s and a magnetic softening. The magnetization vs. temperature curves of quenched samples s showed a pronounced increase of magnetization before reaching the Curie point. The results are discussed taking the knowledge of the physical metallurgy of the martensitic stainless steels into account.
Changes of the Magnetic Properties during Heat Treatment in AISI 304
Periodica Polytechnica Transportation Engineering
The aim of this study was to evaluate changes of the magnetic properties during heat treatment in austenitic stainless steel AISI 304. Investigated changes were caused by plastic deformation in material. Specific composition of alloying elements in austenitic stainless steels has got influence on their deformation behavior. Samples were heat treated before measurement of magnetic properties in different intervals of temperatures. The first series of measurements has shown, that it is necessary to make more precise analysis of temperature intervals in the second part of experiment. For verification of structural changes in material there was used hardness test Vickers method and observation by light optical microscope. There was proven that AISI 304 is slightly magnetic after cold forming, although in general it is considered as non-magnetic.