Tungsten heavy alloys (WHAs) belong to a group of two-phase composites, based on W-Ni-Cu and W-Ni-Fe alloys. Due to their combinations of high density, strength, and ductility, WHAs are used as radiation shields, vibration dampers, kinetic energy penetrators and heavy-duty electrical contacts. This paper presents recent progresses in processing, microstructure, and mechanical properties of WHAs. Various processing techniques for the fabrication of WHAs such as conventional powder metallurgy (PM), advent of powder injection molding (PIM), high-energy ball milling (MA), microwave sintering (MW), and spark-plasma sintering (SPS) are reviewed for alloys. This review reveals that key factors affecting the performance of WHAs are the microstructural factors such as tungsten and matrix composition, chemistry, shape, size and distributions of tungsten particles in matrix, and interface-bonding strength between the tungsten particle and matrix in addition to processing factors. SPS approach has a better performance than those of others, followed by extrusion process. Moreover, deformation behaviors of WHA penetrator and depleted uranium (DU) Ti alloy impacting at normal incidence both rigid and thick mild steel target are studied and modelled as elastic thermoviscoplastic. Height of the mushroomed region is smaller for <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2130003pt" id="M1" height="8.91176pt" version="1.1" viewBox="-0.0498162 -8.69876 39.5321 8.91176" width="39.5321pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-223" d="M545 106L524 126C493 85 467 65 455 65C438 65 427 113 405 238C448 295 498 362 543 439L533 448L478 435C453 386 423 331 398 295H395C370 404 347 448 282 448C169 448 23 309 23 153C23 54 65 -12 128 -12C203 -12 283 70 339 155H341C360 29 380 -12 411 -12C444 -12 491 11 545 106ZM333 204C265 95 210 54 169 54C137 54 113 96 113 171C113 302 191 405 252 405C301 405 318 306 333 204Z"/></g><g transform="matrix(.0135,0,0,-0.0135,11.482,0)"><path id="g117-34" d="M535 323V373H52V323H535ZM535 138V188H52V138H535Z"/></g><g transform="matrix(.0135,0,0,-0.0135,23.219,0)"><path id="g113-49" d="M241 635C89 635 35 457 35 312C35 153 89 -12 240 -12C390 -12 443 166 443 312C443 466 390 635 241 635ZM238 602C329 602 354 454 354 312C354 172 330 22 240 22C152 22 124 173 124 313S148 602 238 602Z"/></g><g transform="matrix(.0135,0,0,-0.0135,29.723,0)"><path id="g113-47" d="M113 -12C146 -12 170 11 170 46C170 78 146 103 114 103S58 78 58 46C58 11 82 -12 113 -12Z"/></g><g transform="matrix(.0135,0,0,-0.0135,32.812,0)"><path id="g113-52" d="M285 378C315 398 338 416 353 432C373 451 384 474 384 503C384 579 325 635 236 635H235C182 635 136 610 108 579L65 516L85 496C110 533 150 575 205 575C258 575 300 543 300 481C300 407 232 369 141 339L147 310C163 315 188 321 211 321C268 321 338 284 338 192C338 94 288 40 217 40C160 40 119 68 93 91C85 98 77 97 69 91C60 84 47 71 46 58C44 46 48 35 62 22C75 10 116 -12 162 -12C234 -12 424 62 424 224C424 297 373 359 285 376V378Z"/></g></svg> and it forms sooner in each penetrator as compared to that for <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-0.2130003pt" id="M2" height="8.91176pt" version="1.1" viewBox="-0.0498162 -8.69876 39.5321 8.91176" width="39.5321pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><use xlink:href="#g113-223"/></g><g transform="matrix(.0135,0,0,-0.0135,11.482,0)"><use xlink:href="#g117-34"/></g><g transform="matrix(.0135,0,0,-0.0135,23.219,0)"><use xlink:href="#g113-49"/></g><g transform="matrix(.0135,0,0,-0.0135,29.723,0)"><use xlink:href="#g113-47"/></g><g transform="matrix(.0135,0,0,-0.0135,32.812,0)"><path id="g113-51" d="M412 140C382 77 369 73 315 73H129L270 222C362 320 402 379 402 466C402 571 322 635 234 635C177 635 130 609 99 576L42 495L64 475C90 514 133 568 201 568C274 568 318 519 318 435C318 349 255 267 193 193C144 135 87 78 32 23V0H405C417 45 427 89 440 131L412 140Z"/></g></svg>.

Y. &#x15e;ahin

Recent Progress in Processing of Tungsten Heavy Alloys

The heat transfer from a fluidized bed to the cooling jacket of the vessel has been studied for various powders at minimum fluidization conditions, by both convection and conduction approaches. These heat transfer characteristics are important as the point of transition between packed and fluidized bed operations and are needed in designing heat transfer operations where bubble-flow is not permitted. The effective thermal conductivity of the emulsion moreover determines the contact resistance at the heating or cooling surface, as used in packet renewal models to predict the wall-to-bed heat transfer. In expressing the overall heat transfer phenomenon as a convective heat transfer coefficient, it was found that the results could be fitted by <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-5.76pt" id="M1" height="17.8381pt" version="1.1" viewBox="-0.0498162 -12.0781 104.226 17.8381" width="104.226pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g190-79" d="M719 650H483V622C553 619 576 606 581 560C585 532 588 487 588 394V148H585L167 650H20V622C67 618 88 610 109 585C127 562 129 557 129 484V264C129 173 126 124 123 93C118 44 92 31 35 28V0H272V28C204 32 181 44 176 95C173 124 170 172 170 264V515H172L598 -9H629V394C629 487 631 532 635 563C639 606 663 619 719 622V650Z"/></g><g transform="matrix(.0135,0,0,-0.0135,10.104,0)"><path id="g190-118" d="M518 50L491 51C452 54 444 60 444 110V444C429 441 405 437 377 434C348 430 314 427 287 426V403L323 397C356 392 365 386 365 333V99C331 66 293 51 257 51C212 51 169 75 169 164V299C169 366 169 413 172 444C156 441 128 437 101 433C75 430 50 427 29 426V403L57 397C82 391 90 386 90 333V137C90 29 147 -12 214 -12C241 -12 262 -4 291 13S342 48 365 65V-6L371 -12C390 -7 415 1 441 8C468 15 496 21 518 24V50Z"/></g><g transform="matrix(.0095,0,0,-0.0095,17.325,3.264)"><path id="g190-110" d="M797 0V26C739 32 732 36 732 103V296C732 394 682 449 605 449C576 449 550 437 529 423C504 407 475 389 446 366C425 418 382 449 334 449C303 449 279 437 253 421C222 403 201 385 180 371V452C135 432 85 419 41 411V388C99 379 102 374 102 310V103C102 38 93 32 27 26V0H238V26C189 32 180 38 180 103V338C210 363 250 390 289 390C351 390 377 348 377 275V103C377 37 368 32 306 26V0H520V26C465 32 456 38 456 101V296C456 314 455 326 453 338C491 369 529 390 565 390C628 390 653 345 653 274V107C653 36 642 32 583 26V0H797Z"/></g><g transform="matrix(.0095,0,0,-0.0095,25.121,3.264)"><path id="g190-103" d="M54 437L27 408L31 397H101V103C101 37 94 32 30 26V0H266V25C187 33 180 36 180 110V397H288C299 404 304 428 298 437H180V477C179 562 190 610 203 630C214 647 230 659 256 659C289 659 318 641 337 622C346 612 355 612 364 619C374 627 380 635 383 643C388 655 387 667 378 678C362 697 333 710 299 712C260 707 225 689 189 659C135 613 119 563 112 541S101 490 101 458V437H54Z"/></g><g transform="matrix(.0095,0,0,-0.0095,27.939,3.264)"><path id="g50-45" d="M98 134C72 134 46 117 46 90C46 73 55 65 60 64C95 55 124 32 124 -4C124 -42 95 -68 44 -89L57 -123C122 -104 194 -60 194 22C194 94 136 134 98 134Z"/></g><g transform="matrix(.0095,0,0,-0.0095,30.187,3.264)"><path id="g50-107" d="M400 606C400 634 383 656 353 656C316 656 294 620 294 593C294 564 317 545 343 545C375 545 400 573 400 606ZM366 351C379 413 381 451 356 451C323 451 251 408 183 341L199 313C223 335 267 365 277 365C285 365 284 354 277 312C245 132 222 27 193 -100C182 -148 160 -188 131 -188C113 -188 90 -178 75 -170C64 -164 55 -168 48 -175C38 -185 24 -203 24 -222S48 -257 71 -257C89 -257 131 -241 186 -192C243 -141 286 -46 310 74L366 351Z"/></g><g 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84 37 20 28V0H238V28C162 35 154 45 175 108C188 150 203 192 219 237H432C454 176 474 122 487 83S491 36 428 28V0H673ZM418 280H234C265 362 296 450 328 535H330L418 280Z"/></g><g transform="matrix(.0135,0,0,-0.0135,82.305,0)"><path id="g190-115" d="M181 342V451C133 431 89 419 40 411V388C98 381 102 377 102 311V104C102 38 95 32 33 26V0H263V26C186 32 181 38 181 104V287C203 343 235 372 261 372C277 372 289 366 304 352C310 346 318 345 330 350C349 359 362 379 362 399C362 422 338 449 304 449C256 449 213 393 183 342H181Z"/></g><g transform="matrix(.0095,0,0,-0.0095,87.35,-5.984)"><path id="g50-49" d="M245 635C92 635 37 457 37 312C37 149 91 -12 244 -12C395 -12 449 166 449 312C449 469 395 635 245 635ZM243 598C332 598 358 454 358 312C358 173 334 26 245 26C158 26 128 174 128 313S152 598 243 598Z"/></g><g transform="matrix(.0095,0,0,-0.0095,91.968,-5.984)"><path id="g50-47" d="M117 -12C153 -12 178 12 178 50C178 84 153 110 118 110C84 110 59 84 59 50C59 12 84 -12 117 -12Z"/></g><g transform="matrix(.0095,0,0,-0.0095,94.216,-5.984)"><path id="g50-53" d="M462 177V227H365V632H320C217 496 116 350 21 208V177H284V109C284 43 280 38 190 31V0H451V31C369 38 365 43 365 108V177H462ZM284 227H88C155 336 218 430 282 519H284V227Z"/></g><g transform="matrix(.0095,0,0,-0.0095,98.835,-5.984)"><path id="g50-51" d="M414 144C384 79 371 75 317 75H135L276 221C367 316 408 376 408 465C408 570 327 635 237 635C179 635 131 609 100 575L42 494L67 471C94 510 138 565 205 565C277 565 321 517 321 435C321 348 258 270 195 195C146 137 88 81 33 26V0H411C423 44 433 88 446 135L414 144Z"/></g></svg>.

Huili Zhang

Jan Degr&#xe8;ve

Jan Baeyens

Raf Dewil

Wall-to-Bed Heat Transfer at Minimum Gas-Solid Fluidization

Solid phases of zirconolite-2M with composition Ca0.8M0.2ZrTi2O7 (M = La, Y) have been synthesized through ceramic route and their structures refined to a satisfactory convergence using Rietveld analysis. Zirconolites crystallize in space group C2/c with Z = 8. The powder diffraction data of Ca0.8Y0.2ZrTi2O7 (CZTY) and Ca0.8La0.2ZrTi2O7 (CZTLa) have been subjected to General Structural Analysis System software to arrive at a satisfactory structure fit with Rp = 0.1128 and Rwp = 0.1805 for CZTY and Rp = 0.1178 and Rwp = 0.1874 for CZTLa, respectively. The unit cell parameters are a = 10.1708 (6) &#x1fa;, b = 6.2711 (4), and c = 11.2779 (6) &#x1fa; for CZTY and a = 11.2548 (6) &#x1fa;, b = 6.2601 (4), and c=11.2606 (7) &#x1fa; for CZTLa. Calculated interatomic distances and bond angles are in good agreement with their standard values. Particle size along prominent reflecting planes calculated by Scherrer&#x2019;s formula ranges between 67 and 107&#x2009;nm. The polyhedral (CaO8, ZrO7, and TiO6/TiO5) distortions and valence calculation based on bond strength analysis have been reported. The compositions of the zirconolites were determined using energy dispersive X-ray (EDAX) analysis. Cation site occupancies were determined by applied compositional constraints which were found consistent with the expected zirconolite-2M cation site occupancies.

Ashish Bohre

Kalpana Avasthi

O. P. Shrivastava

Synthesis, Characterization, and Crystal Structure Refinement of Lanthanum and Yttrium Substituted Polycrystalline 2M Type Zirconolite Phases: Ca1-xMxZrTi2O7 (M = Y, La and x = 0.2)

An efficient way to find the workability limit for powder metallurgy parts has been suggested. Compacts of Al-4&#x25;TiC, Al-4&#x25;WC, Al-4&#x25;Fe3C, and Al-4&#x25;Mo2C were produced to the relative density of 0.82 and 0.86 with three different geometries through primary operations of powder metallurgy routes. Each sintered compact was hot deformed to various strain levels till a visible crack appeared at the free surface. Oyane&#x2019;s fracture principle was used to develop a theory to study powder metallurgy compacts. A least square technique was used to determine the constants in fracture criteria and these equations were finally used to find workability limit. It is found that the projected technique was well in agreement with the experimental values.

S. Narayan

A. Rajeshkannan

Workability Behaviour of Powder Metallurgy Aluminium Composites

The internal stress field induced by uniaxial pressing and subsequent convective drying of a green ceramic powder was simulated by the finite element method. A density dependent elastoplastic constitutive law was used for the mechanical modeling of the compaction. A diffusive water transfer equation and a purely elastic behavior with imposed hydrostrain involving shrinkage were applied for the modeling of the drying process. The key material properties (hydrodiffusivity, hydrocontraction coefficient, Young&#x2019;s modulus, Poisson&#x2019;s ratio, and yield surface parameters) had been experimentally measured and introduced as functions of material density and water content. If residual stresses due to the compaction operation were taken into account, the maximum value of the tensile stress at the top external edge of the wheel and at the beginning of the drying process was two times higher than for a stress free green ceramic compact. Beyond the residual stress onset, the compaction operation induced density heterogeneities which had important consequences on the mechanical behavior of the compact.

E. Vidal-Sall&#xe9;

D. Falgon

R. Peczalski

J-C. Boyer

Cumulative Effect of Pressing and Drying on Stress Generation within a Green Ceramic Compact

Experiments in 3 different CFB risers have confirmed that common riser operations can be hampered in a well-defined (U, G) range where choking occurs. Geldart A-type powders were investigated. Experimental results of the choking velocity were empirically correlated, being about 30&#x25; lower than predicted by the correlation of Bi and Fan, but largely exceeding other predictions. Introducing the findings into the operation diagram presented by Mahmoudi et al. adds a region where stable riser operation is impossible. The adapted diagram enables CFB designers to better delineate the operating characteristics.

H. L. Zhang

J. Degr&#xe8;ve

J. Baeyens

R. Dewil

Choking Affects the Operation Diagram of a CFB Riser

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Journal of Powder Technology