JMatPro V6 2 1 FULL Cracked Checked
Fran Bottella
To be presented at Liquid Metal Procession 2003, Sept.21-24 2003, Nancy, France Modelling of the Thermo-Physical and Physical Properties for Solidification of Ni-based superalloys N. Saunders, A. P. Miodownik and J.-Ph. Schill Sente Software Ltd., Surrey Technology Centre, The Surrey Research Park Guildford, Surrey GU2 7YG, U. K. Abstract The thermo-physical and physical properties of the liquid and solid phases are critical components in the modelling of casting simulations. Such properties include the fraction solid transformed, enthalpy release, thermal conductivity, volume and density all as a function of temperature. Due to the difficulty in experimentally determining such properties at solidification temperatures, little information exists for multicomponent alloys. As part of the development of a new computer programme for modelling of materials properties (JMatPro), extensive work has been carried out on the development of sound, physically based models for these properties. Wide ranging results will presented for Ni-based alloys, which will include more detailed information concerning the phases formed during solidification and their composition and the density change of the liquid that intrinsically occurs during solidification due to its change in composition. 1. INTRODUCTION Previous modelling work 1,2,3,4,5,6,7,8 has shown that excellent results can be obtained can be obtained for the phases formed on solidification, and their composition, by using thermodynamic modelling based on the CALPHAD 9 methodology. In particular, CALPHAD methods have been applied to Ni-based Superalloys and results checked in detail against experiment 5,6,7,8 . However, although useful in their own right, both for process modelling and modelling of microstructures, such calculations fall short of supplying physical property data for the phases, which is critical for successful simulation of solidification. At low temperatures, physical properties can be readily measured, although it may be a time-consuming and expensive procedure to obtain all relevant properties. Experimental measurement becomes far more problematical at high temperature and especially if the liquid phase is involved. To this end, it is highly desirable to calculate thermo-physical and physical properties over the complete relevant temperature range for as wide a range of alloys as possible. The present paper describes a methodology that extends the existing CALPHAD models to further calculate properties such as density, thermal conductivity, specific heat (C p ), solidification shrinkage etc., and applies it for Ni-based multicomponent alloys. A significant advantage of the current method is that properties for each phase are calculated so fine detail can be obtained; for example the density change of the liquid during the solidification, which is governed both by an intrinsic change with temperature and by the composition changes that accompany solidification. The current work forms part of the development of a more generalised software package (JMatPro) for the calculation of a wide range of materials properties. 10 A feature of the new programme is that great store has been placed on using models that, as far as possible, are based on sound physical principles rather than purely statistical methods. Thus, many of the shortcomings of methods such as regression analysis can be overcome. For example, the same model and model parameters are used for density calculations for all alloy types, whether it be for a commercially pure Al-alloy or a complex Ni-based superalloy. The paper will discuss briefly the Scheil-Gulliver solidification model that is used to directly calculate phase amounts, C p , enthalpy and latent heat of solidification. Details concerning the creation of a molar volume database that enables a variety of properties to be calculated, such as solidification shrinkage, density, thermal expansion coefficient, will then be presented. The calculation of thermal conductivity and modulus will also be discussed. Examples of the linking of the solidification models with the physical property calculations are made and properties calculated during solidification will be presented. 2. THE SCHEIL-GULLIVER (SG) SOLIDIFICATION MODEL Recently the application of so-called 'Scheil-Gulliver' modelling via a thermodynamic calculation route has led to the ability to predict a number of critical thermo-physical properties for alloys. Such calculations can be computationally very fast and used within solidification packages such as ProCAST 5 . The model assumes
JMatPro 8.0 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The following versions: 8.0, 6.1 and 1.0 are the most frequently downloaded ones by the program users.
After the computer-aided production, industrial-scale wheel casting studies were carried out in Cevher Alloy Wheels Company located in İzmir Aegean Free Trade Zone. First of all, alloys were prepared by using AlSi7 and pure-Al ingots, master alloys and Mg tablets in a tilting type melting furnace with 750 kg Al capacity. The pure-Al ingot and appropriate amount of Mg tablets were added to AlSi7 melt to prepare AlSi5Mgx alloys. Also, AlTi5B1 and AlSr10 master alloys were added to the melt for grain refinement and modification of the microstructure. During the melting process, the composition was checked by optical spectrometry measurements on 5 samples of the liquid metal. After melting, the alloys were degassed for 15 min. This process is for removing dissolved hydrogen gas in the liquid metal and minimizing possible casting defects. After degassing, the melts were transferred to the LPDC unit with transfer crucibles and wheels castings were performed at 745 C. The die made of H13 tool steel is also preheated to 470 C before LPDC process. The die is subjected to pothole coating process with DYCOTE-30 before the casting process to control the heat transfer in the cast part, to have a better surface quality and to leave the mold without deformation. During the production, the same LPDC unit was used for each alloy and 30 sample wheels were cast in different compositions. Also, the cooling rate corresponds to 2.08 C s-1 when it is considered that the casting starts at 745 C, ends at 25 C and the cycle time is 5.45 min for the production of the one wheel. After casting, all of the wheels were subjected to X-Ray control. For the mechanical tests, at least 5 samples were obtained from the relevant parts of each wheel according to DIN EN ISO 6892-1 automotive standard. For tensile tests, the samples also were taken within the scope of DIN 50125 standard and the test was carried out with 50 N pre-load and 0.002 s-1 speed. Also, detailed macro and microscopic examinations were carried out in the spoke, hub and flange regions of the wheel samples based on ISO/IEC 17025 standard. In the metallographic sample preparation phase for microstructural examinations, after grinding with coarse to fine grained (240-2000 sands) abrasive paper, polishing was done with colloidal silica solution. NIKON SMZ1000 stereo microscope was used in macrostructural observations and NIKON LV100 optical microscope working with Clemex image analysis software was used in microstructural examinations.
The use of aluminum in chassis, bumper, and crash boxes has increased in the last 10 years with an increase in the production of electric vehicles in the automotive industry. The extrusion process has also gained importance because it allows mass production. While basic 6xxx series aluminum alloys such as 6060 and 6063 were used in the early stages of the process, later on, 6005A and 6082 alloys, which provide higher strength, have been used. Alloys with higher strength and crash ability are needed with an increase in safety requirements in automotive. In this study, the effect of chemical composition and heat treatment on the intergranular corrosion strength of 6056 alloys was examined. Another aim of this study is not only to produce high strength and ductility alloy but also to provide good corrosion resistance as automotives are used in different environments for several decades. The 6056 alloys are potential candidate materials for the new-generation electrical vehicles in the automobile industry due to their high strength, weldability, machinability, and impact resistance. Therefore, in our work, we produced 6056 alloy samples in a billet form using the direct chill casting method. Then they were homogenized, and billets were extruded as a box profile. Experimental studies were carried out on 6056 alloys with two different chemical compositions and three different heat treatment conditions (T42, T62, and T76) using Method B of EN ISO 11846 standard for corrosion testing. Crack sizes of metallographic sections from corroded areas were calculated g using a scanning electron microscope. As a result, we found that the addition of Mg to 6056 alloys improves corrosion resistance, while copper reduces it. When Zn is added to the alloys, Mg starts to react with it and forms MgZn2, which increases the corrosion progress. Moreover, when heat treatment is applied at T76 conditions, the alloys demonstrate high corrosion resistance.
The use of aluminum alloys in chassis, bumper, and battery carrier systems has increased considerably in the last 10 years to reduce the battery weight of electric vehicles in the automotive industry [5]. In addition to high strength, high ductility of alloys is also required, especially in areas that are exposed to plastic deformation during a crash like bumper and sidewall profiles. For these cases, heat treatment processes applied to aluminum alloys gain significant importance. While the highest strength values for aluminum alloys are obtained with the T6 heat treatment process, the T7 (T76 and T79) heat treatment process is preferred in the automotive industry [6]. In T7, an over-aging process is applied to the alloy; as a result, the mechanical properties that can be reached with the T6 heat treatment process are compromised by approximately 10% [7]. However, the corrosion resistance, high-temperature usability, and ductility of the alloy can be increased with the T7 heat treatment process.
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