Andy Watson

Some experiences modelling the sigma phase in the Ni–V system

Abstract A number of thermodynamic optimisations of the Ni–V system have been carried out using experimental phase diagram and thermodynamic data available from the literature. In each optimisation, a different model was used to describe the thermodynamic properties of the sigma phase. The results of the optimisations have been compared with each other and their shortcomings discussed.

The thermodynamic database COST MP0602 for materials for high-temperature lead-free soldering

The current state of thermodynamic modelling in the field of high-temperature n lead-free soldering is presented. A consistent thermodynamic database, n containing 18 elements (Ag, Al, Au, Bi, Co, Cu, Ga, Ge, Mg, Ni, P, Pb, Pd, n Sb, Sn, Ti and Zn) has been created. The thermodynamic data for the most of n the important binary and selected ternary systems were checked and included n into the database. The database was tested using major commercial software n packages. Such reliable and sophisticated software coupled to reliable n thermodynamic databases are necessary prerequisites for application of n thermodynamics in advanced alloys design.

Critical Assessment 5: Thermodynamic data for vacancies

Abstract The thermodynamic properties of crystalline phases are generally represented well in terms of the compound energy formalism and the model has been implemented in all the major software packages used to calculated phase equilibria. The formalism is particularly successful in modelling defects in crystals, both the formation of holes or vacancies on lattice sites, and the dissolution of atoms on interstitial sublattices. In the former case the formalism may require the definition of data for pure vacancy itself. In this assessment we investigate the possible values for the Gibbs energy of vacancy to be used in the compound energy formalism and show that a value of zero or negative will always lead to unwanted catastrophic stability of the phase.

Experimental study of Fe–C–O based system above 1,000 °C

The paper deals with the study of phase transformation temperatures of the model Fe–C–O based metallic alloys in the high temperature region (above 1,000xa0°C). Six model alloys with graded carbon and oxygen content were prepared and studied. Temperatures of phase transitions were obtained using DTA method (differential thermal analysis). The Setaram SETSYS 18™ (TG/DTA/DSC/TMA) modular experimental system was used for measurements. Influence of composition change (carbon and oxygen content) on shift of phase transformation temperatures is investigated in this paper. New original data (phase transformation temperatures) were obtained in this study. Controlled heating of the alloys was conducted at the rates of 2, 4, 7, 10, 15 and 20xa0°Cxa0min−1. Comparison of the obtained experimental data with the data presented in the literature was also carried out. It follows from comparison of the obtained results with the data accessible in the literature that a lack of experimental data exists, and these available data significantly differ.

Barium – Iron – Oxygen

The first barium ferrite investigated was BaFe12O19 by [1938Ade] who recognized the similarity of its structure with that of the so-called β alumina (Na2O·11Al203) and its isotypy with the mineral known as magnetoplumbite PbFe12O19. The structure of this compound was determined for the first time by [1967Tow] and is in good agreement with more recent studies of [1985Obr, 1992Shi]. The investigation of the Ba-Fe-O ternary system is concerned mainly with the study of BaFe12O19 and related compounds, which have magnetic properties of significant practical importance (Table 1). Barium oxide is also known to stabilize the higher oxidation states of iron, for instance in BaFeO3 in which iron has the valence IV [1970Bel, 1971Zan].

Oxide formation during electric resistance welding of low carbon steels

The influence of Mn and Cr on the formation of surface oxides and their entrapment during electric resistance welding of Si containing low carbon steels was studied using thermodynamic calculations and experimental investigation of the microstructure of the different oxide inclusions within welds on electric resistance welding-fabricated pipes. The process of oxidation during the welding process, its dependence on oxygen content, temperature of oxidation and the composition of ferrite within the parent steel were analysed. It was shown that the most important influence on the type of oxide inclusions formed during welding is the Mn/Si ratio, while Cr has an indirect influence via carbide formation, which increases the relative content of Mn in ferrite.

Carbon – Molybdenum – Titanium

The knowledge of phase relations in the C-Mo-Ti system is very important for several advanced materials, especially for high temperature and wear resistant applications. Main attention is given to the behavior of the B1 type TiC carbides and the MoxC carbides, which strongly influence the properties of industrial materials. Molybdenum alloys are very important candidate materials for such applications because of their high melting point, high thermal conductivity, low sputtering yields etc. On the other hand, there are problems with their mechanical properties at low temperatures (radiation embrittlement). The addition of TiC can significantly improve the low-temperature ductility after irradiation [2005Kit], which strongly improves the practical value of the alloy. TiC based cermets are another important class of materials, used as possible substitutes for the widely used WC-Co based hard metals for cutting applications. They have lower toughness in comparison with the latter, but better wear resistance and high-temperature properties. The presence of Mo improves the properties of such alloys thus increasing the need for detailed information about the phase diagram of C-Mo-Ti system. The first study of the C-Mo-Ti system was an isothermal section at 1710°C published by [1956Alb], which appeared later in the review by [1961Eng], but no new phase diagram data were published here. The quasibinary section of the diagram was described by [1963Ere], [1968Zak, 1969Zak, 1970Zak] studied the Mo rich part of the phase diagram, but the most detailed study of this system was published by [1969Rud, 1970Rud], who studied the liquidus surface and selected isothermal and temperature-composition sections. Other phase diagram sections were also published by [1969Ere, 1970Zak, 1970Ere1, 1970Ere2]. The overviews of experimental results were published by [1981Hol, 1984Hol, 1994McH, 1999Ban], in particular, [1985Ere] gave a comprehensive review of experimental work to date, including their own studies. The review comprised a number of isothermal sections, vertical sections, solidus and liquidus surfaces and a reaction scheme. The theoretical study of C-Mo-Ti system was carried out by [1990Vel], and full assessment of this system was published by [1996Shi], based on the above mentioned experimental results. A general overview of crucial features of the C-Mo-X (X = Ti, W, Ta etc.) phase diagrams was published by [1974Vel, 1988Vel1], nevertheless, no detailed phase diagrams are shown in these two papers. Details of experimental works on the phase equilibria, crystallography and thermodynamics of the ternary C-Mo-Ti system are listed in Table 1. Several authors e.g. [1936Mol, 1972Sam1, 1972Sam2, 1975Sam, 1977Tre, 1979Shu, 2002Kou, 2005Kit] studied material properties of the C-Mo-Ti system, especially with respect to the properties of carbide phases in the Mo-TiC alloys (see Notes on Material Properties and Miscellaneous).

Lead-Free Soldering: Environmentally Friendly Electronics

Abstract The substitution of lead in the electronics industry is one of the key issues in the current drive toward ecological manufacturing. This chapter is aimed at giving an overview of requirements, current situation, problems, and possible development of lead-free soldering and other environmentally friendly joining technologies. It starts with the overview of existing EU regulations and directives. The current situation in the lead-free soldering field is mapped here and a review of the literature, including a patent search, reveals systems and technologies that are at the focus of research effort. New approaches that employ the use of theoretical modeling in the development of new materials is briefly discussed in this chapter. The final part shows the difficulties that the industry faces when implementing new materials into production. The task of this part is to summarize the likely impacts of the phasing out of lead-containing solders for industry, especially small- and medium-sized enterprises.

[O77] The reassessment of the Al-Cu and Cu-Zn systems with respect to the γ–brass phase

The 4-sublattice model was used for modeling of thermodynamic properties of gamma-brass phase ensuring compatibility of phase description in higher order systems, e.g. mutual solubility of phases of the same structure type.