An investigation of contact deformation,fracture, and fatigue behavior in bulk metallic glasses

This article presents the results of a study of the contact-induced deformation, fracture/resistance-curve behavior, and fatigue-crack-growth behavior of two bulk metallic glasses (BMGs), one in the fully amorphous condition and the other containing a dispersion of microscale crystallites. Hertzian contact indentation experiments were performed on both materials under monotonic loading conditions. The contact-induced deformation characteristics observed in the Hertzian experiments are then compared with the stress distribution determined from finite-element analyses. In addition, the cracking patterns associated with resistance-curve behavior in single-edge notched bend (SENB) specimens are incorporated into a fracture-mechanics framework for the estimation of toughening due to microcrack shielding. The predicted steady-state toughness values are shown to be comparable to the measured values obtained from resistance-curve experiments. Subsequently, fatigue-crack-growth rare data obtained at stress ratios of 0.1 and 0.5 are presented and analyzed using a crack-tip opening displacement (CTOD) model. The implications of the results are then discussed.     

Transition metal alloys of extraordinary stability; An example of generalized Lewis-acid-base interactions in metallic systems

The Engel theory of metals predicts unusually high thermodynamic stability for certain classes of alloys of transition metals for which generalized Lewis-acid-base interactions are possible. To test these predictions, phase equilibria were studied for ternary systems of Zr, C, and the transition metals Re, Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au. Similar literature data for Nb, Ta, Hf, Th, Y, Ce, Er, and Pu with Re, Ru, Rh, Ir, Pt, and Au were evaluated. Thermodynamic data for the carbides of Zr, Hf, Th, Nb, Ta, U, and Y were critically evaluated, tabulated for 1200 to 2300 K, and used to fix the Gibbs energies of formation in kcal/g-atom of alloy, or their limits, for the binary phases of the above metals. In addition, for Zr, activity coefficients and excess Gibbs energies are tabulated. The predicted high stabilities for alloys of Rh, Ir, Pd, and Pt are confirmed with excess Gibbs energies ranging to —100 kcal/g-atom and activity coefficients as low as 10^-12 for zirconium or hafnium in dilute solutions of platinum at 1800 K. Some of the properties of these unusually stable compounds have been measured. An erratum to this article is available at .     

An experimental investigation of "point" job evaluation systems.

3 raters evaluated a sample of 82 jobs on 17 requirements. The study aim was to determine extent of influence through manipulation or forcing by evaluators. Both forced and unforced conditions were used. 5 factors emerged from the analysis in both conditions, with the 3 predominant factors in each being similar. "Forcing had the effect of increasing the job level variance from 86% in unforced ratings to 98% in forced ratings." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation of high temperature thermodynamic properties in the Pt-Zr and Pt-Hf systems

High-temperature thermodynamic properties of Pt−Zr alloys containing 2 to 25 at. pct Zr and Pt−Hf alloys containing 20 to 25 at. pct Hf have been measured over the temperature range 1100 to 1400 K by a galvanic cell technique using a thoria-based electrolyte. Activities of Zr and Hf show large negative deviations from Raoult's Law; at 1300 K and 23 at. pct Zr of Hf, for instance,a _Zr=6.5×10⁻¹⁶ anda _Hf=7.9×10⁻¹⁷. Correlation of emf results with X-ray phase data enables calculation of standard free energies of formation of the intermetallic compounds ZrPt₅, ZrPt₃, and HfPt₃. At 1300 K ΔG _f ⁰ (ZrPt₅) =−92,680 cal/mole; ΔG _f ⁰ (ZrPt₃)=−91,740 cal/mole; and ΔG _f ⁰ (HfPt₃)=−97,350 cal/mole. The high stabilities of phases in the Pt−Ti, Pt−Zr, and Pt−Hf systems verify the predictions of the Engel-Brewer correlation. The large negative entropies of formation of TiPt₃, ZrPt₃ are discussed. Applications including side reactions in fuel cells and thermocouple systems are mentioned. P. J. MESCHTER, formerly a Graduate Student at the University of Pennsylvania This paper is based upon a dissertation submitted by P. J. Meschter in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of Pennsylvania.     

Thermodynamic properties of binary metallic systems containing intermetallic compounds

If the thermodynamic activity of the components in a binary metallic system A-B, which contains intermetallic compounds (A _m B or AB _l , where m, l = 1, 2, 3, …), is calculated on the basis of ideal associated solutions, reasonable accuracy may be obtained by means of the assumption that the chemical composition and thermodynamic properties of the associates are the same as for the intermetallic compounds.