Thixoforming : Semi-solid Metal Processing

More documents

Recommendations

Info

8.4 Multifunctional PVD Composites for Thixoforming Mouldsj255 applications [25]. The major problem with the common DC sputtering technology is the so-called target poisoning depending on the oxygen ratio. The chemical reaction takes place not only on the substrate, but also on the chamber walls and on the target. When a certain oxygen partial pressure is exceeded, the target is totally poisoned and the deposition rate decreases. On the other hand, a low oxygen partial pressure leads to the deposition of metallic, conductive material. For this reason, the partial pressure has to be controlled closely. Another problem is the formation of an insulating layer on the shielding and the targets, which leads to potential displacement and an increasing tendency for arcing, respectively. This makes the reactive DC sputtering unattractive for industrial applications. To solve these problems, Schiller et al. used pulsed power supplies [27, 28]. A further beneficial effect of the pulse technology is the increase in the plasma density [28]. In 1998, Belkind et al. examined the influence of different pulse parameters on the reactive sputtering of alumina by applying the unipolar pulse technique [29]. The critical frequency where arcing occurs depends on cathode current, pressure and reverse time (duration of the positive discharging time) and lies in the range 1–80 kHz. It increases with decreasing pressure and reverse time. 8.4.1.1 Experimental Details for the Development of g-Al 2O 3 The development of crystalline g-Al2O3 for application in tool inserts was done using a Model Z400 laboratory sputtering PVD coating machine (Leybold Heraeus, Hanau, Germany). For deposition of the bilayer system (TiAlN/g-Al2O3, a Melec SPIK 2000 A pulsed power supply was used. For the target material, an aluminium metal target of 99.2% purity and a titanium–aluminium metal target (50:50 at.%) with a purity of 99.9% was used. Prior to deposition, the vacuum chamber is evacuated to a base pressure of 7.8 10 5 mbar. The process gas argon and the reactive gases nitrogen and oxygen possess a purity of 99.999%. The Ar, N2 and O2 flow rates are controlled independently by mass flow controllers. For the TiAlN interlayer the N2 concentration was kept constant at 30%. while the oxygen flow was varied between 2 and 16%. The variation of the deposition parameters is reported in Table 8.2. The substrates were also precleaned by r.f. sputtering for 30 min using the parameters listed in Table 8.2. 8.4.1.2 Results and Discussion The challenge for the development of crystalline Al2O3 coatings lies in avoiding the formation of a dielectric reactive layer at the targets. A strong O 2 flow-dependent hysteresis effect is observed and needs to be stabilized within a small process window. At a significant oxygen flow rate, the effect of target poisoning is observed by a drop in voltage and deposition rate (coating time ¼ constant) (see Figure 8.14). This effect marks the transition region of the target s surface from a metallic (zone 1) to a crystalline (zone 2) and finally to an amorphous zone (zone 3). By forming a nanocrystalline structure, an increase in mechanical properties and hardness was achieved for an oxygen flow rate of 2.25 sccm (Figure 8.14) [30]. To investigate the high-temperature stability during the thixoforming process, high-temperature X-ray diffraction (XRD) measurements were performed with the
256j 8 Tool Technologies for Forming of Semi-solid Metals Table 8.2 Deposition parameters for TiAlN/g-Al2O3. Process parameters Etching phase Interlayer (Ti 0.5Al 0.5)N Top layer Al 2O 3 Process pressure (Pa) 1 0.5 0.2–0.5 Process time (s) 1800 3600 3600 R.f. power (W) 100 — — R.f. frequency (MHz) 13.56 — — N2, O2 concentration (%) — 30 2–16 Pulse parameters Pulse mode/pulse power (W) — Unipolar/500 Bipolar/800 Pulse sequence (ton-/toff /tonþ/toffþ] (ms) — 5/25 5–13/5–13/5–13/5–13 M.f. (kHz) — 33 19.2–50 Pulse voltage (V) — 637 280–360 Pulse current (A) — 0.8 0.9–2 developed coatings. These investigations showed the stability of the g-Al2O3 up to 1000 C [25]. To enhance the weak adhesion of crystalline Al2O3 (10 N scratch load without an interlayer), the developed TiAlN–g-Al2O3 system offers a critical scratch load up to 70 N on the hot working steel substrates. Figure 8.15 shows the deposited g-Al2O3 without an interlayer (Figure 8.15a) and with the TiAlN interlayer (Figure 8.15b). 8.4.1.3 Summary of the Development of the TiAlN–g-Al2O3 Bilayer System By using pulsed power supplies, it is possible to deposit fine crystalline g-Al2O3 with good mechanical and tribological properties compared with an uncoated material. The coated samples are analysed by common thin-film techniques such as nanoindentation and XRD. The deposition of g-Al2O3 is limited to a very low deposition Figure 8.14 Hardness and coating thickness depending on the O 2 flow (coating time ¼ constant).
Page 2:
Thixoforming Semi-solid Metal Proce
Page 5 and 6:
Further Reading Herlach, D. M. (ed.
Page 7 and 8:
The Editors Prof. Dr. G. Hirt Insti
Page 9 and 10:
VI Contents 1.3.5.2 Other Aluminium
Page 11 and 12:
VIII Contents 4.6.1 Thixocasting 13
Page 13 and 14:
X Contents 7.4.2 Isothermal Non-ste
Page 15 and 16:
XII Contents 9.4.1.3 Simulation Res
Page 18:
Preface Semi-solid forming of metal
Page 21 and 22:
XVIII List of Contributors Andreas
Page 23 and 24:
XX List of Contributors Alexander S
Page 25 and 26:
2j 1 Semi-solid Forming of Aluminiu
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
10j 1 Semi-solid Forming of Alumini
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Table 1.1 Overview of semi-solid pr
Page 47 and 48:
Page 49 and 50:
Page 52:
Part One Material Fundamentals of M
Page 55 and 56:
32j 2 Metallurgical Aspects of SSM
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
44j 3 Material Aspects of Steel Thi
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Temperature (ºC) 1550 1500 1450 14
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
100j 3 Material Aspects of Steel Th
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
106j 4 Design of Al and Al-Li Alloy
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 170 and 171:
5 Thermochemical Simulation of Phas
Page 172 and 173:
here it can be assumed that the dat
Page 174 and 175:
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
Page 193 and 194:
170j 6 Modelling the Flow Behaviour
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228: 204j 6 Modelling the Flow Behaviour
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
Page 265 and 266: 242j 8 Tool Technologies for Formin
Page 277: 254j 8 Tool Technologies for Formin
Page 329 and 330:
306j 8 Tool Technologies for Formin
Page 331 and 332:
308j 8 Tool Technologies for Formin
Page 334 and 335:
9 Rheocasting of Aluminium Alloys a
Page 336 and 337:
Figure 9.2 Processes for the semi-s
Page 338 and 339:
Two Italian companies gained the fi
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
Page 346 and 347:
Figure 9.12 Components of cartridge
Page 348 and 349:
Figure 9.15 Process adapted multipa
Page 350 and 351:
step-shot experiments. It is also s
Page 352 and 353:
Figure 9.18 (a) Meander tool for fl
Page 354 and 355:
Figure 9.19 (a, b) Wear appears in
Page 356 and 357:
Table 9.2 Temperature determination
Page 358 and 359:
and are plausible on the left. Furt
Page 360 and 361:
Figure 9.27 Development of the micr
Page 362 and 363:
some places can be observed as smal
Page 364 and 365:
Figure 9.31 Simulation of the metal
Page 366 and 367:
Figure 9.33 So-called Constant Temp
Page 368 and 369:
Figure 9.35 Comparison of the micro
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
Page 376 and 377:
homogeneous microstructure and no d
Page 378 and 379:
grain fragment density [mm -1 ] 200
Page 380 and 381:
can be considered for rheocasting o
Page 382 and 383:
Figure 9.44 Microstructure of Zr/Sc
Page 384 and 385:
Figure 9.45 MAGMAsoft simulation: c
Page 386 and 387:
The cooling to the process temperat
Page 388 and 389:
D grain diameter of a circle DGM De
Page 390 and 391:
27 Doppelbauer, M. (2003) Wirtschaf
Page 392 and 393:
10 Thixoforging and Rheoforging of
Page 394 and 395:
1970s [7]. Also, the quality of the
Page 396 and 397:
10.3 Heating and Forming Operations
Page 398 and 399:
With the solution of the Equations
Page 400 and 401:
10.3.1.2 Modelling of Inductive Hea
Page 402 and 403:
material properties have to be cons
Page 404 and 405:
10.3 Heating and Forming Operations
Page 406 and 407:
Figure 10.9 Experimental results, d
Page 408 and 409:
Figure 10.12 Segregation in compone
Page 410 and 411:
10.3.4 Thixoforging of Steel In thi
Page 412 and 413:
10.3.5 Thixojoining of Steel In the
Page 414 and 415:
einforcing element. The possibiliti
Page 416 and 417:
Figure 10.20 The robot controller a
Page 418 and 419:
Figure 10.21 Experimental results w
Page 420 and 421:
Figure 10.24 Design and working pri
Page 422 and 423:
The investigations show that the rh
Page 424 and 425:
Figure 10.31 Scheme of the heat tra
Page 426 and 427:
Table 10.2 Definition of boundary c
Page 428 and 429:
Figure 10.35 Experimental and simul
Page 430 and 431:
References 1 Koesling, D., Tinius,
Page 432:
steel billets into the semi-solid s
Page 435 and 436:
412j 11 Thixoextrusion The followin
Page 437 and 438:
414j 11 Thixoextrusion channel with
Page 439 and 440:
416j 11 Thixoextrusion parameter co
Page 441 and 442:
418j 11 Thixoextrusion Both concept
Page 443 and 444:
420j 11 Thixoextrusion should be ju
Page 445 and 446:
422j 11 Thixoextrusion Figure 11.8
Page 447 and 448:
424j 11 Thixoextrusion Table 11.4 C
Page 449 and 450:
426j 11 Thixoextrusion Temperature
Page 451 and 452:
428j 11 Thixoextrusion impacts. Ext
Page 453 and 454:
Page 455 and 456:
432j 11 Thixoextrusion shell format
Page 457 and 458:
Page 459 and 460:
436j 11 Thixoextrusion Table 11.6 P
Page 461 and 462:
Page 463 and 464:
440j 11 Thixoextrusion solidificati
Page 465 and 466:
442j 11 Thixoextrusion GPa pressure
Page 467 and 468:
444j Index arbitrary volume element
Page 469 and 470:
446j Index equilibrium tests 141 eq
Page 471 and 472:
448j Index - importance 273 ion flu
Page 473 and 474:
450j Index oxygen-sensitive element
Page 475 and 476:
452j Index - thixoforming 241 semi-
Page 477:
454j Index - high pressure 131 - sc
show all

Thixoforming : Semi-solid Metal Processing

Create successful ePaper yourself

Delete template?

Save as template?