Effect of Zr-content on the oxidation and phase transformation of Zr-base amorphous alloys in air

A general analytical phase transformation model has been proposed and successfully applied to describe the crystallization of amorphous alloys. The “additivity rule” is proved to be compatible with the analytical model; the effects of anisotropic growth based on Monte Carlo (MC) simulations is reinterpreted using the analytical approach; and an improved temperature integral is also proved to be compatible with the analytical model. Kinetic analysis basing on the analytical model declares the transformation mechanism, e.g. nucleation, growth and impingement mode. On this basis, the kinetic behaviors of isothermal and non-isothermal crystallization of amorphous Zr50Al10Ni40are analyzed.

Download Full-text

AEM analysis of crystallization in Ti-based amorphous alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075142 ◽

1983 ◽

Vol 41 ◽

pp. 270-271

Author(s):

A.R. Pelton ◽

A.F. Marshall ◽

Y.S. Lee

Keyword(s):

Magnetic Properties ◽

Amorphous Alloys ◽

Amorphous Materials ◽

Isothermal Annealing ◽

Amorphous Matrix ◽

Nucleation And Growth ◽

Current Interest ◽

Amorphous Films ◽

Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Download Full-text

Phase Transformation In Ti-6al-4v Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096175 ◽

1972 ◽

Vol 30 ◽

pp. 584-585

Author(s):

Shiro Fujishiro

Keyword(s):

Phase Transformation ◽

Grain Boundary ◽

Cryogenic Temperature ◽

Β Phase ◽

Heat Treated ◽

Mixed Microstructure ◽

Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

Download Full-text

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089123 ◽

1991 ◽

Vol 49 ◽

pp. 962-963

Author(s):

J. Cooper ◽

O. Popoola ◽

W. M. Kriven

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Glass Matrix ◽

Nickel Sulfide ◽

Plate Glass ◽

Thermal Expansion Mismatch ◽

Volume Increase ◽

Β Phase ◽

Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

Download Full-text

Ion Beam Mixing of Ni-Ti Bilayered Thin Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118345 ◽

1985 ◽

Vol 43 ◽

pp. 290-291

Author(s):

A. K. Rai ◽

R. S. Bhattacharya ◽

M. H. Rashid

Keyword(s):

Crystal Structure ◽

Thin Films ◽

Amorphous Alloys ◽

Ion Beam ◽

Ion Bombardment ◽

High Energy ◽

Mixing Efficiency ◽

Ion Beam Mixing ◽

Enhanced Diffusion ◽

Binary Metal

Ion beam mixing has recently been found to be an effective method of producing amorphous alloys in the binary metal systems where the two original constituent metals are of different crystal structure. The mechanism of ion beam mixing are not well understood yet. Several mechanisms have been proposed to account for the observed mixing phenomena. The first mechanism is enhanced diffusion due to defects created by the incoming ions. Second is the cascade mixing mechanism for which the kinematicel collisional models exist in the literature. Third mechanism is thermal spikes. In the present work we have studied the mixing efficiency and ion beam induced amorphisation of Ni-Ti system under high energy ion bombardment and the results are compared with collisional models. We have employed plan and x-sectional veiw TEM and RBS techniques in the present work.

Download Full-text

AEM of reaction-bonded SiC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122125 ◽

1992 ◽

Vol 50 (1) ◽

pp. 344-345

Author(s):

K Das Chowdhury ◽

R. W. Carpenter ◽

W. Braue

Keyword(s):

Mechanical Properties ◽

Phase Transformation ◽

High Temperature ◽

Epitaxial Growth ◽

Liquid Silicon ◽

Structural Ceramic ◽

Few Data

Research on reaction-bonded SiC (RBSiC) is aimed at developing a reliable structural ceramic with improved mechanical properties. The starting materials for RBSiC were Si,C and α-SiC powder. The formation of the complex microstructure of RBSiC involves (i) solution of carbon in liquid silicon, (ii) nucleation and epitaxial growth of secondary β-SiC on the original α-SiC grains followed by (iii) β>α-SiC phase transformation of newly formed SiC. Due to their coherent nature, epitaxial SiC/SiC interfaces are considered to be segregation-free and “strong” with respect to their effect on the mechanical properties of RBSiC. But the “weak” Si/SiC interface limits its use in high temperature situations. However, few data exist on the structure and chemistry of these interfaces. Microanalytical results obtained by parallel EELS and HREM imaging are reported here.

Download Full-text