Recent works made by the authors' research group on magnetic field-induced martensitic transformations are reviewed, which are concerned with some ferrous alloys and steels. Main results of the works are as follows: The effect of magnetic fields on martensitic transformation start temperature is quantitatively explained by cumulative three energies, that is, magnetostatic energy, high field susceptibility energy and forced volume magnetostriction energy. Antiferromagnetic order in the parent phase suppresses the martensitic transformation. The appearance of magnetoelastic martensitic transformation is newly found in an ausaged Fe-Ni-Co-Ti alloy. Futhermore, directional growth of magnetic field-induced martensite plates is observed parallel to the magnetic field.
Design and development of superconducting structures require basic research on electromagnetic fracture mechanics. In the theory of brittle fracture in a strong magnetic field, usually we consider linear electromagnetic elastic solutions of crack problems. Examples including analysis of electromagnetic elastic crack problems are reviewed to show the effect of magnetic field on the mechanical behavior of cracked materials. Many electrically conducting materials are used in magnetic and electric current fields. First, the electromagnetic elastic problems of conducting cracked materials are analized to show the effect of electromagnetic force. The current flow is disturbed by the presence of the crack and the electromagnetic body force is caused by the interaction between the magnetic field and the disturbed current. If the electrically conducting material is used in the strong magnetic field, we must consider the effect of induced current. Secondly, scattering of time harmonic waves by a crack in an electrically conducting material under a magnetic field is analized to show this effect. If a ferromagnetic material is used in a magnetic field, we must consider the effect of induced magnetization. Lastly, the fracture and deformation of a soft ferromagnetic material in a magnetic field is investigated to show this effect.
A change of an energy system, an advance and a development of a cryogenic engineering are going to yield some new type cryogenic structures or equipments. Many materials have been used and are planed in application to these structures, and at the same time, a material development to aim to satisfy a certain property has been conducted. In this review report, the cryogenic structural materials are summarized, and their joining method and joint properties are related briefly.