Thixoforming : Semi-solid Metal Processing

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content with decreasing temperature. Microhardness measurements of the light grain boundary areas indicate that it is mainly a matter of a layer of retained austenite with fine carbide precipitations, the development of which is strongly dependent on the cooling conditions. In conclusion, it can be noted that an identification of the phase components is impossible due to the structural morphology and the low contrast of the metallographic images. Furthermore, it can be assumed based on the thermodynamic calculations and due to the higher process temperature and the, therefore, higher diffusion ability that as with steel X210CrW12, a considerable amount of secondary austenite is still formed during quenching and is subsequently martensitically transformed, so that it is metallographically not distinguishable. 3.4.2.2 Microprobe Examination of the Quenched 100Cr6 Samples In Figure 3.29, a BSE image and the corresponding element distribution images of the elements silicon, manganese, chromium and carbon of a sample quenched from 1425 C are depicted. Only chromium exhibits significant concentration differences, the other element being distributed fairly homogeneously. As in steel X210CrW12, the formerly liquid phase is chromium enriched, although, by means of line-scan measurements, no conclusion about the former solid–liquid phase boundary can be drawn. Thermodynamic calculations support the high segregation aptness of the chromium around the end of the solidification of the liquid phase (Figure 3.30). Because of the faster diffusion due to the higher process temperature of steel 100Cr6, the concentration differences of the two phases are considerably less pronounced than for steel X210CrW12, so that no determination of the liquid-phase contents is possible by means of element distribution. Figure 3.29 BSE image (a) and element distribution images (Si, Mn, Cr, C) with dimensions 500 500 mm of a specimen quenched from 1425 C (b). 3.4 Structural Parameter Development and Material Selectionj79
80j 3 Material Aspects of Steel Thixoforming Figure 3.30 Carbon, chromium, silicon and manganese contents of the line-scan measurement of a sample quenched from 1425 C. A comparison of the chromium and carbon distributions (Figure 3.29) and a close inspection of the line scan (Figure 3.30) indicate that carbides precipitated in the segregated grain boundary areas whereas most of the segregated zones consist of retained austenite. In the areas in which higher chromium contents and marginally higher manganese contents without simultaneously raised carbon concentrations exist, retained austenite should be present in a metastable form due to a concurrent reduction of the Ms temperature. In the right part of the line scan, detection of carbide can be assumed, due to higher chromium and carbon concentrations, with simultaneous depletion of manganese. It is clear from the manganese distribution that the manganese concentration in the neighbourhood of the carbide is slightly raised and the carbide is, therefore, surrounded by austenite with higher stability. A detailed discussion of the structural development is presented with regard to the resulting mechanical properties in Section 3.6. 3.4.2.3 EBSD Measurements of Quenched 100Cr6 Specimens Figure 3.31a shows the BSE image of a specimen quenched from 1425 C. The black areas are fine cracks formed due to the high cooling rate. The image in (b) shows that retained austenite is present in the probably former liquid-phase areas. These can be taken as the lower boundary of the liquid-phase content and can provide a rough indicator of the former structure in some samples. The orientation measurement in (c) shows a random distribution of the martensitic structure. An accurate differentiation of the formerly solid and liquid sample areas is, however, not possible. The quenching experiments on steel 100Cr6 confirm the tendency of the thermodynamic calculations that in comparison with the partial liquid X210CrW12 no liquid-phase determination is possible due to the diffusion of the elements in the
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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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Page 52: Part One Material Fundamentals of M
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Page 67 and 68: 44j 3 Material Aspects of Steel Thi
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Page 113 and 114: Temperature (ºC) 1550 1500 1450 14
Page 123 and 124: 100j 3 Material Aspects of Steel Th
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130j 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
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Figure 5.4 Composition profiles of
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It is clear that C has by far the s
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Figure 5.7 The density of X210CrW12
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5.3 Calculations for the Bearing St
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Figure 5.11 Composition profiles of
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Figure 5.14 The density of 100Cr6.
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area which is available for heat tr
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Part Two Modelling the Flow Behavio
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170j 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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