Thixoforming : Semi-solid Metal Processing

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Figure 9.35 Comparison of the microstructures with and without the channel, using a ceramic and a steel sheet mould. Table 9.3 Variable parameters in the cooling channel process. Parameter channel Parameter container 9.4 Rheoroutej345 Cooling: Cooling time: Contact time melt channel: inclination, length Temperature of the container Material Material Temperature (TC) of the channel Wall thickness Pouring temperature (TP) Dimensions and form Additional cooling Flow rate: Supercooling: Pouring rate Temperature of the melt directly after flowing into the container Inclination Length (duration of acceleration)
346j 9 Rheocasting of Aluminium Alloys and Thixocasting of Steels Table 9.4 Variables of the cooling channel process. a No. TC ( C) TPv ( C) TGn ( C) mB (g) mR (g) mG (g) Dm (%) tP (s) Dt12 (min) 1 141 653 613 1623 347 1970 17,6 5,9 5:58 2 137 642 613 1759 382 2141 17,8 5,2 — 3 137 633 613 1496 425 1921 22,1 4,7 — 4 144 638 614 1575 360 1935 18,6 4,2 4:30 5 144 633 611 1561 402 1963 20,5 3,5 4:29 6 140 629 613 1465 467 1932 24,2 3,6 5:54 7 143 628 612 1517 487 2004 24,3 3,4 5:08 8 144 634 613 1646 371 2017 18,4 2,9 4:45 9 139 642 614 1682 331 2013 16,4 2,9 5:27 a TC, temperature of the channel; TPv, temperature of the melt before pouring; TGn, temperature of the melt after pouring; mB, weight of the billet; m R, weight of the remaining metal on the channel ¼ metal loss; m G, poured metal ¼ m B þ m V; Dm, percentage metal loss; t P, pouring time; Dt 12, time between pourings. Theincreaseinthegraindensityisaffectedbytwomechanisms:thecoolingofthemelt due to the channel contact and the shearing of formed dendrites as a result of the flow. The residence time of the melt on the channel is the decisive factor for the temperature decrease of the melt, provided that the channel temperature is not varied. This residence time is changeable on the one hand by varying the channel length. Over the channel length the melt cools continuously. With a longer flow length the melt becomes increasingly colder, but in addition the metal loss also increases. Because the pouring temperature should be as low as possible (less hydrogen absorption and lower costs for heating of the melt), pouring of 15 C supercooled melt is useful. In this respect, the channel length is chosen appropriately. Simulations accomplished with MAGMAsoft confirmed this result. On the other hand, the contact time between the melt and the channel can be influenced by the pouring rate and the channel inclination. Both affect the flow rate of the melt and, as a consequence, the shearing of the <strong>solid</strong> phase and the residence time. As a result of this, the flow length could be chosen to be shorter if the channel were to be more tilted. In that case, the shearing rate would be increased. Under the influence of shear, the transformation from dendritic to globular grains occurs [43]. This effect was shown [41] while using the so-called cooling slope of the new rheocasting process. Comparing the microstructures of the remnant metal on the cooling slope from the top of the slope with those from the bottom, a transition from dendritic to globular microstructure takes place. Due to the fluid flow, melting of the dendrite arms and deformation of the dendrites occur, resulting in crystal multiplication [39, 40]; the grain density increases. The main difference between the cooling slope and cooling channel is the inclination (45–5 ). This forces a much higher shearing on the cooling slope. To evaluate this effect in the cooling channel process, the remnant metal on the cooling channel was investigated.
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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
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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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Page 334 and 335: 9 Rheocasting of Aluminium Alloys a
Page 336 and 337: Figure 9.2 Processes for the semi-s
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Page 340 and 341: 9.2 SSM Casting Processesj317 For t
Page 342 and 343: Figure 9.7 Oil pump cover for Honda
Page 344 and 345: Figure 9.9 Middle temperature cours
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Page 348 and 349: Figure 9.15 Process adapted multipa
Page 350 and 351: step-shot experiments. It is also s
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Page 356 and 357: Table 9.2 Temperature determination
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Page 360 and 361: Figure 9.27 Development of the micr
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Page 364 and 365: Figure 9.31 Simulation of the metal
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Page 370 and 371: 9.4 Rheoroutej347 If rounding of th
Page 372 and 373: 9.4.1.2 Parameters: Cooling to the
Page 374 and 375: Figure 9.36 Results of the 2D-MICRE
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Page 382 and 383: Figure 9.44 Microstructure of Zr/Sc
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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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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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