MAGNETIC FREEZING BY USING THE TRANSFORMATION OF MATERIAL

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A new magnetic recording, which uses the phase-transformation of austenitic stainless steel, is proposed. The transformation from austenito to martensite occurs as a result of tribological stress. Martensite is ferromagnetic while austenite is not. memorizing phenomena of magnetic field in stainless steel were observed. After a uniform tensile stress generated the phase-transformation of a stainless steel thin plate in a magnetic field, the magnetic force distribution on the steel surface was measured. The distribution was similar to that of the magnetic field that was induced by the exciting coil. This result means that the information about the external magnetic field distribution was frozen in the tension test specimen. The freezing characteristics obtained by conducting the study were as follws ;1)There is a good correlation between the stress applied by stretching a stainless steel plate and the magnitude of the magnitic force, which is stored in the plate. And the relationship shows good linearity.2)As the amount of plastic deformation increases, both magnetic force and distortion of the frozen field increase. This means that there exists an optimal condition for the freezing. These conditions depend on materials. The optimal stress for SUS 304 is 410 MPa.3)The frozen magnetic field was contained in the stainless steel plate for more than 2 month. the magnetic field is quite stable for the external magnetic field wnen the direction coincides with that of the frozen magnetic field.4)The frozen magnetic field is erased by the irradiation of CO2 laser5)The irradiation of CO2 laser has a capability to be used as a trigger for the freezing of magnetic field.