Fractal analysis of the surface cracks on continuously cast steel slabs

Data concerning the length of longitudinal cracks on the surface of continuously cast steel slabs were collected from two plants. The data were analyzed to find the relation between crack length and crack frequency. The analysis revealed the following.

Effect of Intense Rolling and Folding on the Phase Stability of Amorphous Al-Y-Fe Alloys

A systematic examination of the effect of intense deformation on the crystallization behavior of amorphous Al₈₅Y₁₀Fe₅, Al₈₆Y₉Fe₅, and Al₈₈Y₅Fe₇ alloys demonstrated a strong composition dependence of the crystallization reactions at true strain levels of about −500 pct. Primary crystallization occurs during the deformation of the Al₈₈Y₅Fe₇ alloy, but for the Al₈₆Y₉Fe₅ and Al₈₅Y₁₀Fe₅ alloys, deformation-induced crystallization is not observed at a true strain of about −500 pct. At strain levels of the order of −1200 pct, the Al₈₅Y₁₀Fe₅ alloy develops regions with primary Al, which is not observed during thermal processing of the same amorphous alloy without deformation. In addition, at strain levels of −1200 pct, a deformed Al₈₈Y₇Fe₅ sample displays strong microstructural heterogeneities. Transmission electron microscopy (TEM) analysis showed the presence of nanocrystal dispersions adjacent to shear bands with a total width of about half a micrometer. The results demonstrate that the phase selection during deformation-induced crystallization can deviate from the thermally-induced phase selection. Novel phases and microstructures can thus be obtained from the deformation processing of amorphous alloys. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, FL, under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.

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Effect of Titanium on Microstructure and Mechanical Properties of Cu50Zr50? x Ti x (2.5?≤ x ≤?7.5) Glass Matrix Composites

The microstructure and mechanical properties of Cu₅₀Zr_50−x Ti _x (2.5 ≤ x ≤ 7.5) glass matrix composites have been investigated. The presence of austenitic (Pm-3m)/martensitic phases (P2₁/m and Cm) enhances the plastic deformability significantly. These composites show high yield strength up to 1753 MPa and large plastic strain over 15 pct. Their high strength scales with the volume fraction of glassy matrix and crystalline phase. When the austenitic phase forms instead of the martensite, the work hardening of the composite material increases. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.

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Thermal Stability, Glass-Formation Ability, and Mechanical Properties of (Zr41.2Ti13.8Cu12.5Ni10Be22.5)100?xNbx Amorphous Alloys

Bulk amorphous alloys of (Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5)_100−x Nb _x with x = 0, 5, 11, and 13 were prepared by water quenching. Differential scanning calorimeter (DSC) analysis revealed that the addition of Nb enhances the thermal stability but appreciably decreases the glass-forming ability (GFA) of the alloys. Scanning electron microscope (SEM) and compression tests indicated that the Nb addition effectively improves the strength and plasticity of a Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 amorphous alloy, which benefits from multiple shear bands induced by ductile crystalline phase dispersing in the amorphous matrix. The bulk amorphous alloy with x = 5 exhibits a fracture stress of 2070 MPa and total strain to fracture of 25.8 pct, respectively. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007, during the TMS Annual Meeting in Orlando, FL, under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.

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Structure of Zr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript>100−<Emphasis Type="Italic">x</Emphasis></Subscript> (73 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 77) Metallic Glasses

The structure of hyper-eutectic Zr _x Pt_100−x (73 ≤ x ≤ 77) metallic glasses produced by melt spinning was examined with high-energy synchrotron X-ray diffraction (HEXRD) and fluctuation electron microscopy. In addition, details of the amorphous structure were studied by combining ab initio molecular dynamics and reverse Monte Carlo simulations. Crystallization pathways in these glasses have been reported to vary dramatically with small changes in compositions; however, in the current study, the structures of the different glasses were also observed to vary with composition, particularly the prepeak in the total structure factor that occurs at a Q value of around 17 nm⁻¹. Results from simulations and fluctuation electron microscopy suggest that the medium-range order of the amorphous structure is characterized by extended groups of Pt-centered clusters that increase in frequency, structural order, or spatial organization at higher Pt contents. These clusters may be related to the Zr₅Pt₃ structure, which contains Pt-centered clusters coordinated by 9Zr and 2Pt atoms. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.

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Thermodynamics of the solid phases in the system Fe−Mn−C

Phase relationships in the Fe−Mn−C system in the temperature range 600 to 1100°C have been studied using metallographic and X-ray methods and the electron microprobe. Isothermal sections of the phase diagram of the system are reported based on the present results and those of earlier investigators. The fcc λ-phase (austenite) containing carbon is stable at all values ofy _Mn=x _Mn/(x _Mn+x _Fe) in the range 890 to 1100°C and in a more restricted composition range at lower temperatures. Its composition under conditions of equilibrium with the carbides (Fe, Mn)₃C, (Fe, Mn)₂₃C₆, ε, and liquid are shown for several temperatures. The free energy of formation of the cementite phase, (Fe, Mn)₃C, at 1000°C, from γ-Fe, γ-Mn (undercooled) and graphite is ΔG ₁₂₇₃=−35,790y _Mn−2760y _Fe+3RT (y _Mn lny _Mn+y _Fe lny _Fe). The data show that the alloyed cementite is essentially and ideal mixture of Fe₃C and Mn₃C,i.e., the metal atoms are distributed at random on the metal sites in the lattice. ROBERT BENZ, formerly of the Research Staff, Massachusetts Institute of Technology, Cambridge, Massachusetts