Thixoforming : Semi-solid Metal Processing

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Figure 4.19 Hardness development of step samples derived from an Al–Li–X principle component. 4.6 Preparation of Principle Components from Al–Li Thixoalloysj133 transferred into a ceramic carrier basin and placed in the preheated casting chamber (Foundry Institute of RWTH Aachen). The effect of the solidification rate (wall thickness 1–25 mm) on the casting grain structure was studied by casting into a step form (Figure 4.19). The form was preheated to 250 Cusingthree heater–cooler units. When the component was removed from the form too early, ignition of the casting residue took place that was still in a partially liquid state. During removal from the form, some of the thinner component walls cracked. In general, the alloy AlLi4Mg8Ti displays better flow characteristics and visual surface quality than the alloy Ali4Cu4Ti. Figure 4.20 shows the grain structure of the 25 and 2.5 mm steps for both materials. Both materials display a virtually perfect thixo-grain structure with a pronounced globulitic primary phase. The magnesium-alloyed variant has a significantly smaller particle size of 35 mm than the Al–Li–Cu alloy with 48 mm. The form factor of the globulitic primary phase for both alloys is 0.74. The image analysis evaluation of the samples could not detect any notable signs of mix separation across the step thickness. The solid-phase proportion for the copper-alloyed type is 75% and for the magnesium-alloyed version 65% in both step thicknesses/cooling rates. Selected thixocasting step samples of the two aluminium–lithium alloys underwent T6 heat treatment (AlLi4Mg8, 2 h at 430 C solution annealed, quenched in water, 15 h at 120 C precipitation heat treatment; AlLi4Cu4, 2 h at 510 C solution annealed, quenched in water, 15 h at 120 C precipitation heat treatment). Even after the heat treatment, the globulitic grain structure was retained. In the case of the alloy AlLi4Cu4Ti, several large globulites collected near the surface, which, with 100–150 mm, had double the average grain size than that in the centre of the steps (50–80 mm). In contrast, the alloy AlLi4Mg8Ti displayed a uniform grain size distribution between the centre of the step and the step surface in all steps (Figure 4.21).
134j 4 Design of Al and Al–Li Alloys for Thixoforming Figure 4.20 Microstructures of thixocast step samples (AlLi4Cu4Ti and AlLi4Mg8Ti) [33]. Figure 4.21 Phase separation near the surface of an Al–Li4Cu4 (Al–Li4Cu4Ti) step sample (a) and near the surface of an AlLiMg8 (AlLi4Mg8Ti) step sample (b). 4.6.2 Rheocasting On the basis of the experience with thixocasting, the 0.15 wt% Sc and 0.15 wt% Zr modified alloy AlLi2.1Mg5.5 (A8) was selected, because due to the lower Li and Mg contents the embrittlement is reduced due to minimized intermetallic phase
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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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Page 170 and 171: 5 Thermochemical Simulation of Phas
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Page 174 and 175: Figure 5.2 Calculated temperature v
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Page 180 and 181: Figure 5.7 The density of X210CrW12
Page 182 and 183: 5.3 Calculations for the Bearing St
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Page 188 and 189: area which is available for heat tr
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184j 6 Modelling the Flow Behaviour
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7 A Physical and Micromechanical Mo
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3. Macroscopic averages or homogeni
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displacement boundary conditions or
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and liquid are both assumed to be i
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are the strain rate concentration t
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Semi-solid viscosity (Pa s) into cl
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Load (kN) strain to rupture, leadin
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Load (kN) 7 6 5 4 3 2 1 0 0 7.5 Con
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adius R radius of the spherical inc
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Part Three Tool Technologies for Fo
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242j 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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