Deformation of metallic glasses: Recent developments in theory, simulations, and experiments

Hydrogen-induced intergranular fracture of steels

Phase separation in metallic glasses

Magnetic amorphous alloys obtained by rapid quenching of the melt are excellent soft magnetic materials with a wide range of technological applications. They also represent a significant challenge to the scientific understanding of magnetic materials, since most of the existing theories of solids assume lattice periodicity. For these reasons, the magnetic and other properties of amorphous alloys have been very actively studied over the last decade. In recent years increasing attention has been directed to the fundamental understanding of the structural, thermal and magnetic properties of the amorphous alloys. It is not only scientifically but also technologically important to achieve such an understanding, since the amorphous alloys are, in many respects, so different from conventional crystalline magnetic materials. The author attempts to summarise recent progress in research on magnetic amorphous alloys and critically assesses the present level of understanding of this new class of magnetic materials, focusing mostly on the transition-metal-metalloid glasses. He starts with a review of early developments and a discussion on the nature of glasses and glass formation and proceeds to an extensive discussion of their atomic structure, both from the experimental and theoretical points of view.

https://iopscience.iop.org/article/10.1088/0034-4885/47/12/002/pdf

Magnetic amorphous alloys: physics and technological applications

A thin film magnetic head includes an upper shield section, a lower shield section and a magnetoresistance device section between the upper shield section and the lower shield section. The magnetoresistance device section is connected to the upper shield section and the lower shield section through conductive layers. Current flows through the magnetoresistance device section via the upper shield and the lower shield.

Thin film magnetic head

A compact magnetooptical disk having 500 times the capacity of a 13.34-cm (5.25-in.) floppy disk has been developed for use in coded data storage applications. Low error rates are attained by the use of advanced highly sensitive polarization detection optics and high-quality recording media. Progress in these fields has been based on noise analysis of readout signals. The disk drive can write and erase data by sectors and can also play current write-once-type optical disks. This disk/disk drive unit promises to lead to enhanced storage capacity and to support the current drive to enhance office automation and other information systems.

Compact magnetooptical disk for coded data storage.

A study was made of quenched and tempered laboratory heats of 35 Ni-17 Cr steels doped with P, Sn, or Si in which the hardness, the grain size, and the extent of intergranular segregation of the metalloid dopents were varied The segregation was accomplished by aging treatments of various times at 480 °C It was found that the increases in ductile-brittle transition temperature (ΔTT) were determined completely by the above three variables and that they can be combined in an “embrittlement equation” that permits the calculation of theΔTT that will occur from a particular degree of segregation in a steel of a given hardness and grain size The embrittlement equation contains coefficients which must be determined empirically for each type of steel and embrittling element; however, the equation is derived by a straight-forward Taylor series expansion of theTT as a function of the three variables Each term of the resulting equation can be justified from physical considerations The embrittlement equation can serve as a rational basis for analysis of a given type of steel or for comparisons between types In particular, it allows one to account for variations in hardness and grain size, and to determine the benefits to be gained from control of these two factors

The calculation of transition temperature changes in steels due to temper embrittlement

The structure of an Fe83B17 amorphous alloy was examined in detail, mainly by means of small-angle X-ray scattering (SAXS) measurements. The electron density-density correlation derived from the observed intensity had the following characteristic features: a strong correlation concentrated in the short radial distances within about 1.2 nm and a rather weak correlation towards larger distances. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 1 nm in the amorphous Fe-B alloys, even though phase separation is not present as completely as in the structure model proposed by Boudreaux. Electrical resistivity measurements as well as transmission electron microscope (TEM) observations were performed to investigate the crystallization process. By using the theoretical equation of electrical resistivity reported by Landauer, the temperature dependence for the partially aged amorphous alloys was analysed. The volume fraction of crystalline phase estimated from the present analysis was in good agreement with the results obtained from TEM observation.

Study of the structure and crystallization of an Fe-17 at % B amorphous alloy

PURPOSE: To obtain an amorphous thin film with low coercive force and high initial permeability by sputtering or vapor-depositing an alloy consisting of a nonmetallic element and a rare earth element replaced partially by a metallic element such as Ti, Zr or Hf and the balance essentially transition metallic element. CONSTITUTION: An alloy expressed by a formula M a T b X c Z d is prepared. In the formula M is ≥1 kind of element selected from Fe, Ni and Co, T is ≥1 kind of element selected from Mn, Cr, W, etc., X is ≥1 kind of element selected from Zr, Ti, Y, etc., Z is ≥1 kind of element selected from P, B, C, etc., a+b+c+d= 100, 0≤b≤95, 30≤a+b≤95, 0≤c≤70and 0≤d≤30. The alloy is sputtered or vapor-deposited to manufacture an amorphous thin film. This film is different from a conventional amorphous thin film in alloy composition and has high thermal stability. when the film is magnetized, it shows superior magnetic characteristics, that is, low coercive force and high permeability. COPYRIGHT: (C)1983,JPO&Japio

Manufacture of amorphous thin film

A magnetic head core and a method of fabricating same, wherein a magnetic circuit is constituted by a pair of magnetic films having a V-shaped cross section which face each other at each protrudent section through the gap material. The cross-sectional portion of the V-shaped film is exposed to the surface facing the magnetic recording medium. The protrusions of the magnetic film pair have tip planes parallel to each other and substantially perpendicular to the moving direction of the magnetic recording medium. The tip plane has a width defined by the line of intersection between the plane and the surface facing the magnetic recording medium in correspondence to the recording track width. At least one of the magnetic films has a window for winding an excitation coil. The magnetic film is formed on the non-magnetic protection member having a V-shaped protrusion. The magnetic head has superior recording and reproducing characteristics in a wide frequency band with less rubbing noise, high wear-resistivity and high productivity, and operates without the pseudo gap effect. The magnetic head core is fabricated through the steps of forming a coil winding groove in the gap forming plane of a non-magnetic core block, forming a number of parallel grooves perpendicularly to the winding groove so that a number of V-shaped protrusions are produced, forming a magnetic film on the surface of the protrusions, forming a gap plane after the magnetic film has been coated with non-magnetic material, and splitting the block and then combining the two core blocks to complete a magnetic head core.

Shinji Takayama

Papers

Compact magnetooptical disk for coded data storage.

The calculation of transition temperature changes in steels due to temper embrittlement

Study of the structure and crystallization of an Fe-17 at % B amorphous alloy

Manufacture of amorphous thin film

Magnetic head and method of fabricating same