Abstract

    Over the past decade thermodynamic models have become increasingly used for Ni- and NiFe-based superalloys. However, their applicability often falls short from directly providing the information that is actually required. To overcome such limitations a new computer programme has been developed, called JMatPro (an acronym for Java-based Materials Properties software). The properties which can be calculated are wide ranging, including thermo-physical and physical properties (from room temperature to the liquid state), TTT/CCT diagrams, coarsening of γ' and γ", and mechanical properties. It should be noted that the mechanical properties are calculated as a function of temperature and strain rate up to the melting point. Stress/strain diagrams at any given temperature and strain rate can also be generated. The creep properties that JMatPro provides include steady creep rate, rupture life and rupture strength. A feature of the new programme is that the calculations are based, as far as possible, on sound physical principles rather than purely statistical methods. Thus many of the shortcomings of methods such as regression analysis can be overcome. It allows sensitivity to microstructure to be included for many of the properties and also means that the true inter-relationship between properties can be developed, e.g. in the modelling of creep and precipitation hardening. The purpose of the present paper is to describe the technical background behind the new programme, giving extensive examples of its application and use for superalloys of the 718, 625, 706 and derivative types.

Introduction

    Tools that utilise thermodynamic modelling for exploring the equilibrium and phase relationships in complex materials are being increasingly used in industrial practice for Ni- and NiFe-based superalloys [1,2]. These tools provide significant benefit, but their applicability often falls short from directly providing the information that is actually required. For example, thermodynamic modelling helps towards the understanding of changes in phase constitution of a material as a function of composition or temperature. However, there is then a gap in translating this information into the properties being targeted by the end user, e.g. TTT diagrams, mechanical properties, thermo-physical and physical properties.

    To overcome these limitations a new computer programme has been developed [3], called JMatPro, an acronym for Java-based Materials Properties software. The approach adopted in the development of the new programme has been to augment the thermodynamic calculation by incorporating various theoretical materials models and properties databases that allow a quantitative calculation for the requisite materials property to be made within a larger softwarestructure. The purpose of the present paper is to describe the technical background behind the new programme, and review its use and application to Ni- and NiFe-based superalloys.

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