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Using friction stir processing (FSP) in forming localised or surface composites in castings can be very advantageous and has significant potential for many applications. Consequently, this study was initiated at ACRC to investigate the feasibility of fabricating composites in Al alloy castings via FSP. The study started with the Al A206 alloy matrix via an ex-situ technique, using a pre-machined groove with emplaced reinforcements. Three reinforcement materials (nanosized tantalum powders, nanosized SiC powders, and discontinuous reinforced aluminium) and several key processing parameters (number of FSP passes, the amount of the reinforced materials) were investigated and localised composites were produced successfully. This paper will present the experimental set-up, procedure, the microstructure and properties of the resulting composites, and a discussion of the formation mechanism of the composite and the influences of materials and process on the microstructure and properties.

Casting experiments were conducted to characterise hot tearing in two aluminium alloys (A356 and M206) using an instrumented constrained permanent mould. The thermal history, thermal contraction and the tensile force induced by thermal contraction were monitored during the casting process. The thermal stress was modelled by considering the contact between the solidified metal and the mould. The calculated displacement and tensile load were compared to measured data and reasonably good agreement was observed. Hot tearing tendency of these two aluminium alloys was predicted using a strain based hot tearing model. It was found that M206 not only demonstrated much higher hot tearing tendency than A356, but also the vulnerable locations for hot tearing were different from A356. The predicted hot tearing positions coincide well with those observed in the castings. The effects of mould temperature, mould material and pouring temperature on the susceptibility of hot tearing were also investigated.

Hot tearing is perhaps the pivotal issue defining castability. It is affected by alloy composition as well as processing conditions and variables. Hot tearing is a complex phenomenon in that it lies at the intersection of heat flow, fluid flow and mass flow. Over the years, many theories and models have been proposed, and accordingly, many tests have been developed. Unfortunately, many of the tests that have been proposed are qualitative in nature. The need exists for a simple, reliable and repeatable quantitative test to evaluate hot tearing. The Metal Processing Institute and the CANMET‐Materials Technology Laboratory, both members of the Light Metal Alliance, joined forces to address this need. A quantitative hot tearing test was developed, and the methodology is presented and discussed. The test has been applied to study hot tearing of A356 and M206 alloys. The results are presented and discussed. Protocol and standardised procedures that can be adapted by the metal casting industry is presented.

Semisolid processing is now a commercially successful manufacturing route to produce net-shape parts in automotive industry. The conspicuous results of alloy optimization with thermodynamic simulations for semisolid processing of commercial AM60 alloy were present. The results indicate that the available processing temperature range of AM60 alloy is 170℃. The temperature sensitivity of solid fraction decreases with increasing solid fraction or with decreasing temperature above eutectic reaction temperature of AM60 alloy. When the solid fraction φ(subscript s) is 0.4, corresponding processing temperature is 603.8℃ and the sensitivity –dφ(subscript s)/dT is 0.0184. The effects of various alloying elements on the solidification behavior and SSM processability of AM60 alloy were calculated with Pandat software.

In order to verify the effect of CRP(continuous rheoconversion process) in the preparation of magnesium alloy semisolid billets,AM60 alloy billets were fabricated with CRP,and effects of pouring temperature,slope angle,and length of the reactor on the microstructure of AM60 alloy were investigated.The results show that the grain size is reduced with the decrease of pouring temperature.A small block/rosette grain is obtained when the pouring temperature is less than 680 °C.Therefore,the available temperature process interval/window has to be required.To change slope angle of reactor(from 30° to 45°) is helpful for formation of the small and block/rosette grains.Meanwhile,the reactor with a length of 500 mm is enough for copious nucleation of primary phase.CRP changes the solidification microstructure of billets by controlling the nucleation and growth of the primary phase in melt.

The quench sensitivity of Al–Si–Mg (D357 unmodified and Sr modified), and Al–Si–Mg–-Cu (354 and 319 Sr modified) cast alloys was investigated using a fluidised bed (FB). The average cooling rate of castings in the fluidised bed is lower than those quenched in water; the cooling rate first increases to a certain maximum and then decreases during quenching. The change in the cooling rate during quenching in water was more drastic, where the cooling rate varied from 0 to −80 K s−1 in less than 8 s, as compared with those quenched in FB, where the cooling rate varied from 0 to −14 K s−1 in 18 s. The FB quenching resulted in the formation of several metastable phases in Al–Si–Mg–Cu alloys; in contrast, no such transformation was observed during water quenching. The T4 yield strength of the FB quenched alloys was greater than water quenched alloys owing to the formation of a greater volume fraction of metastable phases in the FB quenched alloys. The tensile properties of T6 treated alloys show that Al–S...

The semi-solid process produces globular instead of dendritic alpha phase and extraordinarily fine fibrous aluminum–silicon eutectic structure, which apparently enables exceptionally high ductility, even when casting copper-containing and secondary alloys that would normally have limited ductility. Contrary to the experience with liquid cast products of the same alloys, semi-solid products can be given a T-5 heat treatment without loss of ductility, a significant advantage in terms of dimensional controls and treatment costs. This paper will describe solidification events that lead to the unique alpha aluminum, eutectic aluminum–silicon and secondary phase structures of semi-solid products and provide evidence to date that it is these unique characteristics that are responsible for exceptional ductility, especially in the T-5 temper.

Aluminum alloy castings are becoming commonplace in important and critical applications in the automotive and aerospace industries where materials failure is not an option. In order to meet such property demands, tight control over the cleanliness of the melt, namely, mitigation of inclusions and dissolved hydrogen must be achieved. Having a cleaner melt will yield sound castings with more reliable performance. In order to control cleanliness, it must first be well defined and measured. Very few techniques exist in industry that can quantitatively measure inclusion levels in-situ. In addition, there are no practical methods in which all quality detractors can be measured simultaneously. The use of laser-induced breakdown spectroscopy (LIBS) has shown promise as a technique to quantify all facets of quality in aluminum melts. Current progress of this work is presented and discussed.

The possibility of developing an analytical quality index chart for applications above room temperature valid for different alloys is explored. The testing temperature and the chemical composition of the material are incorporated into the analysis through their respective effects on the material's strain hardening rate and yield strength. The resulting quality index chart has been used to compare the performance at room temperature, 100°C and 200°C of 16 experimental high-pressure die-cast aluminium alloys in terms of quality index, yield strength and tensile ductility. The best performance at 200°C is observed in alloys with high content of Mg or Cu and Mg and, depending on the Fe and Si content, Mn or Sr. The limitations of the approach are discussed.

Having taken the solid network movement in the two-phase zone into consideration, this paper develops the original local solute redistribution equation. The additional term div V′s in the new equation is dependent on the history of an effective stress σ′ acting upon the solid network. The solidifying isotherm advances quickly and there is not enough time to make the solid network compressible at large cooling rates. With decreasing cooling rate, movement of the isotherm is gradually slowed and there is enough time to make the network deformed. It is suggested that the compressibility due to the normal stress may produce “channel space” filled by unstable flow under the conditions of small cooling rate during solidification. The calculated results have demonstrated that the back-flow toward the centerline increases when the stress is considered.

The requirements and limitations of furnaces and plasma torches for cold hearth remelting processes are discussed and existing transferred arc plasma technology critically reviewed, placing particu...

0 (0) 0 (0) 0 (0) 1 (20) 0 (0) 1 (4) 0 (0) Other, * n (%) 1 (20) 0 (0) 0 (0) 1 (20) 1 (17) 3 (11) 2 (22) 1 (20) 0 (0) 0 (0) 0 (0) 0 (0) 1 (4) 0 (0) GT-1a, n (%) 4 (80) 6 (100) 6 (100) 3 (60) 5 (83) 24 (86) 6 (67) GT-1b, n (%) 0 (0) 0 (0) 0 (0) 2 (40) 1 (17) 3 (11) 3 (33) IL-28B Status CC, n (%) 3 (60) 0 (0) 0 (0) 1 (20) 3 (50) 7 (25) 2 (22) CT, n (%) 2 (40) 4 (67) 6 (100) 4 (80) 2 (33) 18 (64) 6 (67) TT, n (%) 0 (0) 2 (33) 0 (0) 0 (0) 1 (17) 3 (11) 1 (11)

Cutbacks in government funding have resulted in an increased emphasis on research support from industry and other agencies. This paper outlines the development of the Metal Processing Institute at Worcester Polytechnic Institute (USA), achieved through industry-university R&D collaboration.

E.J. Lawitz1, T.D. Boyer2, G.T. Everson3, I.M. Jacobson4, W. Lee5, J.G. McHutchison6, P.J. Pockros7, M.L. Shiffman8, J.M. Vierling9, S. Cruickshank10, B. Armstrong11, T.C. Rodell12, D. Apelian12 1Alamo Medical Research, San Antonio, TX, 2University of Arizona, Tucson, AZ, 3Department of Medicine, University of Colorado Denver, Aurora, CO, 4Department of Medicine, Weill Cornell Medical College, New York, NY, 5Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 6Duke Clinical Research Institute, Duke University Medical Center, Durham, NC, 7The Scripps Clinical Research Center, La Jolla, CA, 8Hepatology Section, Virginia Commonwealth University Medical Center, Richmond, VA, 9Department of Medicine and Surgery, Baylor College of Medicine, Houston, TX, 10Cruickshank and Associates, Santa Barbara, CA, 11QST Consultations, Allendale, MI, 12GlobeImmune, Inc., Louisville, CO, USA

The fundamentals of spray deposition via the Osprey™ process have been analysed to identify critical process parameters, and to understand their effect on the integrity of the preforms produced. From the resulting knowledge base, the directly controlled process parameters may be related to the shape and structure of the preform. Our approach has involved the development of an integral model for spray casting using established theoretical principles to describe droplet-gas interactions in flight and subsequent droplet consolidation at the substrate. The model is implemented to predict the fraction of liquid in the spray upon impact, the temperature distribution in the consolidated material, and the shape/geometry of the preform produced. Five primary process parameters can be controlled to optimise two critical dependent parameters; the latter are the physical and thermal characteristics of (i) the metal spray at impact, i.e. ‘deposition condition’, and (ii) the partially liquid layer on the surfa...

370 WHOLE RECOMBINANT YEAST THERAPEUTIC VACCINE GENERATES HBV X, S, AND CORE ANTIGEN-SPECIFIC RESPONSES IN MURINE AND HUMAN T CELLS T.H. King, A.J. Gehring, A. Bertoletti, Z.Z. Ho, W.E. Delaney, M. Subramanian, J. McHutchison, Z. Guo, Y. Lu, L. U’Ren, D.L. Mann, D. Bellgrau, D. Apelian. Research and Development, GlobeImmune, Inc., Louisville, CO, USA; Infection & Immunity Programme, Singapore Institute for Clinical Sciences, Agency for Science Technology and Research (A*Star), Singapore, Gilead Sciences, Inc., Foster City, CA, Integrated Department of Immunology, University of Colorado Denver School of Medicine, Denver, CO, USA E-mail: arlenet@globeimmune.com

A third putative sigma factor gene, sigC, has been isolated from Myxococcus xanthus by using the sigA gene (formerly rpoD of M. xanthus) as a probe. The nucleotide sequence of sigC has been determined, and an open reading frame of 295 residues (M(r) = 33,430) has been identified. The deduced amino acid sequence of sigC exhibits the features which are characteristic of other bacterial sigma factors. The characterization of a sigC-lacZ strain has demonstrated that sigC expression is induced immediately after cells enter into the developmental cycle and is dramatically reduced at the onset of sporulation. A deletion mutant of sigC grows normally in vegetative culture and is able to develop normally. However, in contrast to the wild-type cells, the sigC deletion mutant cells became capable of forming fruiting bodies and myxospores on semirich agar plates. This suggests that sigC may play a role in expression of genes involved in negatively regulating the initiation of fruiting body formation.

1181 PHARMACOGENOMIC ANALYSIS REVEALS IMPROVED VIROLOGIC RESPONSE IN ALL IL-28B GENOTYPES IN NAIVE GENOTYPE 1 CHRONIC HCV PATIENTS TREATED WITH GI-5005 THERAPEUTIC VACCINE PLUS PEG-IFN/RIBAVIRIN J.G. McHutchison, A.J. Thompson, I.M. Jacobson, T.D. Boyer, E.R. Schiff, G.T. Everson, J.M. Vierling, M.L. Shiffman, R.S. Brown, A.M. Di Bisceglie, S.C. Gordon, W.M. Lee, Z. Guo, T.H. King, B. Armstrong, T.C. Rodell, D. Apelian. Duke Clinical Research Institute, Duke University Medical Center, Durham, NC, Center for the Study of Hepatitis C, Weill Cornell Medical College, New York, NY, Department of Medicine, University of Arizona College of Medicine, Tucson, AZ, Center for Liver Diseases, University of Miami School of Medicine, Miami, FL, Department of Medicine, University of Colorado Denver, Aurora, CO, Department of Medicine and Surgery, Baylor College of Medicine, St. Luke’s Episcopal Hospital, Houston, TX, Liver Institute of Virginia, Bon Secours Health System, Newport News, VA, Columbia University College of Physicians & Surgeons, New York, NY, Saint Louis University, St. Louis, MO, Henry Ford Hospital, Detroit, MI, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, GlobeImmune, Inc., Louisville, CO, QST Consultations, LTD, Allendale, MI, USA E-mail: mchut001@mc.duke.edu

276 WEEK 4 HCVRNA IS THE OPTIMAL PREDICTOR OF SVR IN BOTH HIV POSITIVE AND NEGATIVE SUBJECTS WITHIN THE AUSTRALIAN TRIAL IN ACUTE HCV G.V. Matthews, J. Grebely, M. Hellard, B. Yeung, P. Marks, W. Rawlinson, J. Kaldor, G.J. Dore, ATAHC Study Group. National Centre in HIV Epidemiology and Clinical Research (NCHECR), University of New South Wales, Sydney, NSW, Burnet Institute, Melbourne, VIC, Virology Division, SEALS Microbiology, Prince of Wales Hospital, Sydney, NSW, Australia E-mail: gmatthews@nchecr.unsw.edu.au

Premium quality aluminum alloy castings are used extensively in various applications requiring a high strength to weight ratio such as in aerospace, automotive and other structural components. The mechanical properties in these structure-sensitive alloys are determined primarily by the secondary dendrite arm spacing and the morphology of interdendritic phases. In addition, the amount of porosity in the casting and the inclusion concentration have strong influence on fracture, fatigue and impact properties. During the production of the casting, various molten metal processing techniques can be implemented to control the microstructural parameters. These melt treatments include grain refinement with Ti-B, eutectic modification with Sr or Na, degassing with purge gases and filtration of inclusions. Recent developments in these areas are reviewed and salient results of ongoing investigations in our laboratory are presented.

Cast aluminum alloys are susceptible to extensive microporosity formation during solidification. This microporosity originates from the liberation of dissolved hydrogen upon freezing and from the volume contraction resulting from the liquid-solid transformation. The fundamental mechanisms associated with microporosity formation during solidification of A356.2 alloy have been investigated. The effects of initial hydrogen concentration, cooling rate and other process variables on pore size and distribution have been studied with simple test castings. The amount and distribution of porosity have been evaluated by image analysis techniques and density measurements. The results indicate that the pore density is essentially constant for various hydrogen concentrations while the pore size and amount of porosity increases with the initial hydrogen content in the liquid metal. The experimental data have been used to formulate a mathematical model to simulate microstructure evolution and pore formation in equiaxed structures. The model yields data on microstructural parameters such as dendrite arm spacing, grain size, amount of porosity and pore size. It has been shown that the predicted values compare well with experimental results.

The lost foam process has generated considerable interest among foundrymen because of the inherent advantages associated with the production of the casting. It has been predicted that the number of foundries utilizing this innovative process will continue to increase rapidly over the next few years. The principal feature of this casting technique is the use of foamed polymer patterns for the production of the component. On contact with the liquid metal, the polymer pattern undergoes thermal degradation through a series of complex transitions to produce liquid and gaseous degradation products. The formation of these degradation products in the mold has a significant effect on the solidification behavior and on the microstructural parameters. Furthermore, the interaction of the degradation products with the solidifying metal may introduce various defects in the casting which are unique to this process. The fundamental aspects associated with the solidification of lost foam castings have been described. The effects of polymer degradation on microstructural characteristics and on defects have been discussed.

Mold fluxes are routinely used during the continuous casting of steel. It has been shown that the viscosity of a flux has a significant effect on the slab surface characteristics. However, no syste...

A laboratory apparatus was constructed to atomize metal alloys by forcing them through sintered ceramic disc filters. The process combines filtration of oxides and/or undesirable second phase particles with atomization. Sintered Al2O3 and SiO2 disc filters with average pore sizes in the range of 36 to 150 Μm were used. The effectiveness of various filters in removing “synthetic inclusions” from Al-Ti-B melts was studied. 2 to 10 Μm size TiB2 particles were successfully filtered out. Atomization experiments were done with pure aluminium and 7075 aluminium alloy. Spherical powders, 150 to 2000 Μm in size, of 7075 aluminium alloy with secondary dendrite arm spacings between 4 to 8 Μm, were cold compacted and extruded into a billet. Room temperature longitudinal properties of the billet in T6 condition were: YS 80×103 psi, UTS 94.3×103 psi, elongation 15% and R.A. 42%.

A preliminary investigation has been conducted to evaluate the influence of Sr modification on the solution heat-treatment response of hypoeutectic Al-Si-Mg (A356.0) alloys. Modified and unmodified...

The electron beam and plasma melting processes are critically reviewed and compared. The principles of each process as it applies to melting of metallic alloys are reviewed and the similarities and differences between the two processes are highlighted. The commercial applications of both electron beam and plasma melting are discussed from a general point of view, and the discussion is then focused by comparing the parallel processing characteristics of titanium.

The production of sound castings often entails supplying adequate amounts of feed metal duringsolidification of the casting. If the feed metal is insufficient, several defects such as porosity, shrinkage and surface sinks can occur in the casting. The extensive data and information in this area has been reviewed in order to obtain a fundamental understanding of the complex phenomena occurring during feeding of aluminum castings. The influence of process parameters such as alloy composition, grain refinement, modification and cooling rate on feeding properties has been analyzed. Various modeling techniques that have been adopted to study the feeding behavior have been described.

The metallurgical quality of simple lost foam castings has been evaluated. Strips of constant thickness were produced under carefully controlled conditions with alloys 319, 356 and 390. The castings were examined by optical and scanning electron microscopy. The mechanical properties were estimated from machined tensile specimens. The results indicate that because of endothermic degradation of the polymer pattern at the metal front, steep thermal gradients are present in the casting. Consequently, dendrite arm spacing and grain size decrease with increasing distances along the length of flow. Furthermore, the distribution and the morphology of Si, Cu and Fe-rich phases depend on location in the casting. The porosity levels in the casting have been estimated by two different techniques to be of the order of 1.5 to 2%. Porosity levels of up to 7% have been detected near the surface of the casting. The ultimate tensile strength and %elongation increase slowly with distance from the downsprue. Defects such as folds and black inclusions are often observed on fracture surfaces.

The need for cleanliness and tighter control over the content and size of nonmetallic particulates (inclusions) in superalloys is a real and severe one. The newer, advanced superalloys for jet engines are continually being subjected to significantly higher stresses and service temperatures than their earlier predecessors. As a result, the tolerance levels for defects in these alloys has markedly decreased in recent years. Defects ranging from 0.05 0.76 mm (0.002-0.03 inches) can be of critical size in highly alloyed superalloys operating under highly stressed LCF conditions. Such defects are one to two orders of magnitude smaller than those tolerated by the conventionally processed wrought alloys (1).

Background on the mechanisms and kinetics of filtration is discussed and the Drexel mathematical model is further elaborated and updated to encompass filtration at the higher temperatures encountered in steels and superalloys. A novel mathematical analysis of inclusion trajectory is also presented. The aluminum-TiB2 study has been extended to evaluate a ceramic foam filter. A low temperature model study of liquid inclusion filtration is described and discussed. Reference is made to ongoing work in superalloy and steel filtration, counter-current gas filtration, filter characterization and flow visualization.

Hot tearing has been an issue for many casting alloys, and much work has been devoted over the years to understanding the underlying mechanism, and to be able to mitigate it during casting. Unfortunately, the literature and therefore our understanding to date has been a bit muddled, as conflicting data and theories exist. In addition, many of the tests that have been developed to evaluate hot tearing have been qualitative in nature. Through the Light Metals Alliance, WPI’s Metal Processing Institute and CANMET joined forces in 2006 to clarify our understanding of hot tearing and to enable us to control it during casting. This paper contains an overview of the authors’ work; describes the quantitative test that was developed and discusses the processing variables that are needed to control and to mitigate hot tearing.