N. Saunders

Modelling phase transformations and material properties critical to the prediction of distortion during the heat treatment of steels

This paper describes the recent development of models in JMatPro for the calculation of phase transformations and material properties that are critical to the prediction of distortion during the heat treatment of steels. The success of these models is based on the accurate description of all the major phase transformations taking place, including the formation of ferrite, pearlite, bainite and martensite, as well as the calculation of the properties of the different phases formed during the heat treatment process. One advantage of the current models is that they can be applied to many types of steels, including medium- to high-alloy types. A wide range of properties such as density, thermal expansion coefficient, thermal conductivity, strength and hardness can be calculated, all as a function of time, temperature and cooling rate, even for an arbitrary cooling profile. The material data calculated from JMatPro have been exported directly to Finite Element (FE)/Finite Difference(FD)-based packages for forging/deformation simulation.

Modeling Phase Transformations and Material Properties Critical to Processing Simulation of Steels

This article describes the development of JMatPro, a computer software that can provide many of the material properties required by processing simulation. The success of the model is based on accurate description of all major phase transformations taking place, as well as calculation of the properties of different phases formed during the heat treatment process. Predictive phase transformation models in the past mainly concerned carbon and low alloy steels. An advantage of the current model is that it can be applied to many types of steels, including medium to high alloy types. In addition to TTT/CCT diagrams, a wide range of physical, thermophysical, and mechanical properties, including strength and stress-strain curves, can be calculated.

Metastable Phase Formation in Multi-Component Aluminium Alloys

Many Aluminium alloys use the precipitation of metastable phases to generate optimum properties. The effect of including additional structures such as θ’ and GP zones is described in the context of a hierarchy of metastable structures. Extending a Thermodynamic data base that has been designed solely to deal with equilibrium conditions is a vital prerequisite to handling the heattreatment of aluminium alloys. It is then possible to generate TTT and CCT diagrams, using the Johnson-Mehl-Avrami treatment previously applied in to other materials providing provision is made for the presence of supersaturated quenched-in vacancies. Calculations using JMatPro are given for the expected behavior of commercial aluminium alloys of increasing complexity, including AA319, AA6061 and AA7075.

Modelling the Strain-Life Relationship of Commercial Alloys

Premature fatigue fractures in structural components are a major problem in the manufacturing industry. The challenge for modellers has been to deliver reliable fatigue-analysis tools, because over-designing components is becoming an increasingly unattractive solution to the problem. Currently software packages exist for fatigue simulation of components or systems. However, a common feature of such software is that they all require the fatigue properties of the materials used. When such information is not available, the fatigue simulation cannot proceed until relevant experimental measurements are carried out, which can be both time-consuming and very costly. It is the aim of the current work to help solve this dilemma by developing models that can calculate the strain-life relationship not only at room temperature but also high temperatures. This work extends previous successful models for predicting the monotonic material properties of commercial alloys as a function of alloy chemistry, heat treatment, temperature and strain rate. In the present paper, attempts are made to model the high temperature fatigue properties of some engineering alloys. The effect of strain rate and cyclic loading frequency on fatigue properties are also discussed.© 2007 ASME

Modelling of Thermodynamic, Thermophysical and Physical Properties of Lead-Free Solder Alloys

The demand for new and improved lead-free solder (LFS) alloys grows steadily as the need for reliable lead-free electronic products increases. Thermodynamic calculations have proved to be an important tool in providing information for the design and understanding of new LFS systems. However, such tools often fall short from directly providing the information that is actually required by the end users, such as physical and thermophysical properties. In the present work, models have been created such that a full set of such properties can be calculated for solder alloys for the multi-component system Sn-Ag-Al-Au-Bi-Cu-In-Ni-Pb-Sb-Zn. The properties, given for both the overall alloy or for each phase if required, include coefficient of thermal expansion, densities, various modulii, thermal conductivity, liquid surface tension and viscosity, all as a function of composition and temperature (extending into the liquid state)