carbide particles are smaller than 100 A and line up to make needle-like shapes. Needle directions are scattered, but for the N-type carbide the average needle direction is [531]M and for the R-type carbide it is [532]M.The carbide contains nickel as well as iron. Its carbon content is considered to decrease with increasing nickel. Superstructure reflections do not appear in the R-type carbide. This is ascribed to a disorder in the carbon atom arrangement caused by the replacement of iron by nickel. The superstructure reflections from the N-type carbide show frequently an intensity anormaly. An explanation is given on the basis of an antiphase domain model with respect to the carbon atom arrangement in the carbide. This gives that in some carbide particles antiphase domain boundaries may be formed in
The glass forming ability of a Mg62Cu26Y12 alloy was delineated by theories of crystallization kinetics. The viscosity of the molten Mg62Cu26Y12 alloy above its melting point was measured by using a rotational viscometer. The temperature dependence of the viscosity derived from the free volume theory was extrapolated to the undercooled liquid region by the Fulcher-Vogel expression, i.e., η=5.78×10-5exp
[7293.6/(T-255.6)] where η is given in cP and T in K. Furthermore, the C–C–T curve was derived from the isothermal crystallization T–T–T curve which had been constructed based on the mechanism of homogeneous nucleation and crystal growth. From such a curve, the critical cooling rate required to form glassy state was derived to be 98° C/s.
The crystallization temperature, the associated activation energy and the crystallized structure of a bulk amorphous Mg62Cu26Y12 alloy with a diameter of 2.5 mm were studied. It possesses a one-step crystallization behavior. The crystallization reaction was found to be represented by: AM(M
G
62
C
u
26
Y
12)→Mg2Cu+MgY+CuY+Mg, ( T
x
=188°C, E
a
c
=134 kJ/mol) where AM represents the amorphous state, T
x the crystallization temperature at an infinitesimal heating rate, and E
ac the associated activation energy. The amount of crystalline phases were found to be Mg2Cu:MgY:CuY=76:17:7. The Mg phase is identifiable only by high resolution electron microscopy, not by X-ray diffraction. The crystallization leads to a sharp rise in electrical resistivity which is reversed to those of iron-based amorphous alloys.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.