A new matched thermochemical diagram for vacuum refining of nickel and cupronickel alloys

Sulfur and oxygen dissolved in nickel and cupronickel melts can be remwed as gaseous oxides of sulfur by a vacuum treatment. Presented in this paper is a new matched thermcxhemical disgran~ that permit.. direct evaluation of the equilibrium partial pressure of SO, as a function of temperature wer an alloy of specified compition. The matched thermochemical diagram consists of a central plot which shows the integral Gibbs' energy of mixing for the binary system SO, at different temperatures. The central plot is flanked on either side by terminal plots of the chemical potentials of oxygen and sulfur, as functions of temperature, for different alloy compositions. By projecting the chemical wtentials of oxygen and sulfur from the terminal lots on to the central diagram, ihe equilibrium partial pressure of S0,can be directly ;cad on the nomograms on the central plot at different temperatures. The matched therrnochemical diagrams are useful in assuring the efficiency of vacuum refining.

On the Structural Stability of Melt Spun Ribbons of Fe95-x Zr (x) B4Cu1 (x=7 and 9) Alloys and Correlation with Their Magnetic Properties

Melt spun ribbons of Fe95-x Zr (x) B4Cu1 with x = 7 (Z7B4) and 9 (Z9B4) alloys have been prepared, and their structure and magnetic properties have been evaluated using XRD, DSC, TEM, VSM, and Mossbauer spectroscopy. The glass forming ability (GFA) of both alloys has been calculated theoretically using thermodynamical parameters, and Z9B4 alloy is found to possess higher GFA than that of Z7B4 alloy which is validated by XRD results. On annealing, the amorphous Z7B4 ribbon crystallizes into nanocrystalline alpha-Fe, whereas amorphous Z9B4 ribbon shows two-stage crystallization process, first partially to bcc solid solution which is then transformed to nanocrystalline alpha-Fe and Fe2Zr phases exhibiting bimodal distribution. A detailed phase analysis using Mossbauer spectroscopy through hyperfine field distribution of phases has been carried out to understand the crystallization behavior of Z7B4 and Z9B4 alloy ribbons. In order to understand the phase transformation behavior of Z7B4 and Z9B4 ribbons, molar Gibbs free energies of amorphous, alpha-Fe, and Fe2Zr phases have been evaluated. It is found that in case of Z7B4, alpha-Fe is always a stable phase, whereas Fe2Zr is stable at higher temperature for Z9B4. (C) The Minerals, Metals & Materials Society and ASM International 2015