Thixoforming : Semi-solid Metal Processing

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Figure 6.36 Experimental setup, T-shaped die. 6.2 Numerical Modelling of Flow Behaviourj203 Model Parameter Determination and Adjustment The model parameters m, n, t0, k and C (see Equation 6.1) were determined on the basis of the step change shear rate experiments and also shear rate ramp experiments at a reference solid content f S,ref. of 52% The rheological experiments led to reliable results for the yield stress t0, the flow exponent n and the consistency coefficient k. These model parameters are related to steady-state conditions. The determination of the isostructure flow exponent m and the rate constant c (Equation 6.5), which describe the transient behaviour of the material, suffers from a slight uncertainty. Ordinary die filling processes do not last longer than approximately 0.5 s. During this time, the semi-solid alloy undergoes a lot of shear rate changes and jumps. Hence the time span for a shear rate jump is in the range of milliseconds. So far there is no possibility of acquiring viscosity values at these time scales with conventional rheometers. A further problem arises from the permeability coefficient kP used in the two-phase model. In order to overcome these problems, a special approach of parameter adjustment has been developed (Figure 6.37). The aim is to achieve congruence between numerical and experimental results. The filling experiments are carried out under isothermal conditions. Varying the filling velocity and the initial solid fraction of the metallic suspension leads to different filling pressures, flow patterns and spatial distributions of solid content. The simulation starts with a set of parameters determined on the basis of the rheological experiments performed and a first guess of the permeability coefficient. As long as no congruence of the flow front contour, the solid fraction distribution and the filling pressure is achieved, a new simulation with modified flow exponent m, rate constant c and permeability coefficient k P is carried out. Two-phase Simulation Using the obtained set of material parameters, the T-shaped die-filling experiment described above was simulated using the two-phase model implemented into the solving algorithm PETERA. In order to show that the flow is mainly influenced by segregation effects, one-phase simulations considering yield
204j 6 Modelling the Flow Behaviour of Semi-solid Metal Alloys Figure 6.37 Procedure for parameter determination and adjustment. stress, shear thinning and thixotropic behaviour are also performed. Figure 6.38 shows a comparison of the experimentally obtained flow patterns, and the flow patterns obtained using one- and two-phase simulations. The isothermal experiments were carried out at piston velocities of 10, 50 and 100 mm s 1 , an initial solid Figure 6.38 Isothermal experiment, one- and two-phase simulation: flow front comparison.
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Thixoforming Semi-solid Metal Proce
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Further Reading Herlach, D. M. (ed.
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The Editors Prof. Dr. G. Hirt Insti
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VI Contents 1.3.5.2 Other Aluminium
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VIII Contents 4.6.1 Thixocasting 13
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X Contents 7.4.2 Isothermal Non-ste
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XII Contents 9.4.1.3 Simulation Res
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Preface Semi-solid forming of metal
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XVIII List of Contributors Andreas
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XX List of Contributors Alexander S
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2j 1 Semi-solid Forming of Aluminiu
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10j 1 Semi-solid Forming of Alumini
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Table 1.1 Overview of semi-solid pr
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Part One Material Fundamentals of M
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32j 2 Metallurgical Aspects of SSM
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44j 3 Material Aspects of Steel Thi
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Temperature (ºC) 1550 1500 1450 14
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100j 3 Material Aspects of Steel Th
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106j 4 Design of Al and Al-Li Alloy
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5 Thermochemical Simulation of Phas
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here it can be assumed that the dat
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Figure 5.2 Calculated temperature v
Page 176 and 177: Figure 5.4 Composition profiles of
Page 178 and 179: It is clear that C has by far the s
Page 180 and 181: Figure 5.7 The density of X210CrW12
Page 182 and 183: 5.3 Calculations for the Bearing St
Page 184 and 185: Figure 5.11 Composition profiles of
Page 186 and 187: Figure 5.14 The density of 100Cr6.
Page 188 and 189: area which is available for heat tr
Page 190: Part Two Modelling the Flow Behavio
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Page 244 and 245: 7 A Physical and Micromechanical Mo
Page 246 and 247: 3. Macroscopic averages or homogeni
Page 248 and 249: displacement boundary conditions or
Page 250 and 251: and liquid are both assumed to be i
Page 252 and 253: are the strain rate concentration t
Page 254 and 255: Semi-solid viscosity (Pa s) into cl
Page 256 and 257: Load (kN) strain to rupture, leadin
Page 258 and 259: Load (kN) 7 6 5 4 3 2 1 0 0 7.5 Con
Page 260 and 261: adius R radius of the spherical inc
Page 262: Part Three Tool Technologies for Fo
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254j 8 Tool Technologies for Formin
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9 Rheocasting of Aluminium Alloys a
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Figure 9.2 Processes for the semi-s
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Two Italian companies gained the fi
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9.2 SSM Casting Processesj317 For t
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Figure 9.7 Oil pump cover for Honda
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Figure 9.9 Middle temperature cours
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Figure 9.12 Components of cartridge
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Figure 9.15 Process adapted multipa
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step-shot experiments. It is also s
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Figure 9.18 (a) Meander tool for fl
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Figure 9.19 (a, b) Wear appears in
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Table 9.2 Temperature determination
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and are plausible on the left. Furt
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Figure 9.27 Development of the micr
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some places can be observed as smal
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Figure 9.31 Simulation of the metal
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Figure 9.33 So-called Constant Temp
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Figure 9.35 Comparison of the micro
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9.4 Rheoroutej347 If rounding of th
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9.4.1.2 Parameters: Cooling to the
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Figure 9.36 Results of the 2D-MICRE
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homogeneous microstructure and no d
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grain fragment density [mm -1 ] 200
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can be considered for rheocasting o
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Figure 9.44 Microstructure of Zr/Sc
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Figure 9.45 MAGMAsoft simulation: c
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The cooling to the process temperat
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D grain diameter of a circle DGM De
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27 Doppelbauer, M. (2003) Wirtschaf
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10 Thixoforging and Rheoforging of
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1970s [7]. Also, the quality of the
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10.3 Heating and Forming Operations
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With the solution of the Equations
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10.3.1.2 Modelling of Inductive Hea
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material properties have to be cons
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10.3 Heating and Forming Operations
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Figure 10.9 Experimental results, d
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Figure 10.12 Segregation in compone
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10.3.4 Thixoforging of Steel In thi
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10.3.5 Thixojoining of Steel In the
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einforcing element. The possibiliti
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Figure 10.20 The robot controller a
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Figure 10.21 Experimental results w
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Figure 10.24 Design and working pri
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The investigations show that the rh
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Figure 10.31 Scheme of the heat tra
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Table 10.2 Definition of boundary c
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Figure 10.35 Experimental and simul
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References 1 Koesling, D., Tinius,
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steel billets into the semi-solid s
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412j 11 Thixoextrusion The followin
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414j 11 Thixoextrusion channel with
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416j 11 Thixoextrusion parameter co
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418j 11 Thixoextrusion Both concept
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420j 11 Thixoextrusion should be ju
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422j 11 Thixoextrusion Figure 11.8
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424j 11 Thixoextrusion Table 11.4 C
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426j 11 Thixoextrusion Temperature
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428j 11 Thixoextrusion impacts. Ext
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432j 11 Thixoextrusion shell format
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436j 11 Thixoextrusion Table 11.6 P
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440j 11 Thixoextrusion solidificati
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442j 11 Thixoextrusion GPa pressure
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444j Index arbitrary volume element
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446j Index equilibrium tests 141 eq
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448j Index - importance 273 ion flu
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450j Index oxygen-sensitive element
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452j Index - thixoforming 241 semi-
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454j Index - high pressure 131 - sc
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Thixoforming : Semi-solid Metal Processing

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