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High Cooling Rate (high + cooling_rate)
Selected AbstractsSynthesis and Properties of Al-Ni-La Bulk Metallic Glass,ADVANCED ENGINEERING MATERIALS, Issue 7 2009Juan Mu Al85.5Ni9.5La5 bulk metallic glass (BMG) with a size of 1,mm is synthesized for the first time through a two-step melt treatment. The treatment effectively removes the local structural ordering and high-temperature phases, as well as allowing a high cooling rate. The sample displays good mechanical properties. The compressive fracture strength is about 1180,MPa, which is higher than that of most Mg-based BMGs and Al alloys. [source] The mathematical model of solidification latent heat under high cooling rateHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2006Yao Shan Abstract Treatment of solidification latent heat is a key point in solidification simulation by the finite difference method. When latent heat is dealt with in a traditional method of equivalent latent heat, it was found that heat was increased when casting with a high cooling rate, and then the simulation result was distorted. In this paper, a new method is proposed to deal with solidification latent heat. Moreover, a mathematical model was suggested, in which the latent heat can be dealt with accurately under high or normal cooling rates. By contrasting the simulation results from this new method with the traditional one, it was indicated that this new model can obtain more accurate simulation results than the traditional model under high or normal cooling rates. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 115,121, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20104 [source] Vertical extrusion and middle crustal spreading of omphacite granulite: a model of syn-convergent exhumation (Bohemian Massif, Czech Republic)JOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2004típská Abstract The exhumation of eclogite facies granulites (Omp,Plg,Grt,Qtz,Rt) in the Rychleby Mts, eastern Czech Republic, was a localised process initiated by buckling of crustal layers in a thickened orogenic root. Folding and post-buckle flattening was followed by the main stage of exhumation that is characterized by vertical ductile extrusion. This process is documented by structural data, and the vertical ascent of rocks from a depth of c. 70 to c. 35 km is documented by metamorphic petrology. SHRIMP 206Pb/238U and 207Pb/206Pb evaporation zircon ages of 342 ± 5 and 341.4 ± 0.7 Ma date peak metamorphic conditions. The next stage of exhumation was associated with sideways flat thrusting associated with lateral viscous spreading of granulites and surrounding rocks over indenting adjacent continental crust at a depth of c. 35,30 km. This stage was associated with syntectonic intrusion of a granodiorite sill at 345,339 Ma, emplaced at a crustal depth of c. 25 km. The time required for cooling of the sill as well as for heating of the country rocks brackets this event to a maximum of 250 000 years. Therefore, similar ages of crystallization for the granodiorite magma and the peak of eclogite facies metamorphism of the granulite suggest a very short period of exhumation, limited by the analytical errors of the dating methods. Our calculations suggest that the initial exhumation rate during vertical extrusion was 3,15 mm yr,1, followed by an exhumation rate of 24,40 mm yr,1 during further uplift along a magma-lubricated shear zone. The extrusion stage of exhumation was associated with a high cooling rate, which decreased during the stage of lateral spreading. [source] Refractive Index Drop Observed After Precision Molding of Optical Elements: A Quantitative Understanding Based on the Tool,Narayanaswamy,Moynihan ModelJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Ulrich Fotheringham The room-temperature refractive index is measured for three different prior cooling rates (approximately 10, 50, and 250 K/h) for two glasses especially developed for precision molding. The empirical logarithmic relationship between the cooling rate and the refractive index is also reproduced for the comparatively high cooling rate of ca. 250 K/h. The same relationship is found in a simulation of these cooling rates by the semiempirical Tool,Narayanaswamy,Moynihan model for structural relaxation, with the necessary parameters obtained from differential scanning calorimetry and temperature jump experiments. The measured and the simulated refractive indices coincide within the limits of experimental error. The results demonstrate that the index drop, which is observed when these glasses are first cooled at a regular optical cooling rate (e.g., 2 K/h), and then precision molded (typical cooling rate 1000 K/h), can be understood considering the concepts of structural relaxation. [source] Fabrication of Fe,Cr,Al Oxide Dispersion Strengthened PM2000 Alloy Using Selective Laser Melting,ADVANCED ENGINEERING MATERIALS, Issue 7 2009John C. Walker Rapid prototyping using the selective laser melting process has been successfully used in the manufacture of solid walls from melt sensitive mechanically alloyed PM2000 FeCrAl ODS powder. Despite melting of the powder, the technique allowed the retention of the nanoscale oxide dispersion due to the high cooling rates. Results showed that coarsening and agglomeration of ODS particles was more dependent on laser scan speed than the maximum laser power. [source] Scanning electron microscopy and transmission electron microscopy microstructural investigation of high-speed tool steel after Nd:YAG pulsed laser meltingJOURNAL OF MICROSCOPY, Issue 1 2006S. KAC Summary This article presents the microstructure of a pulsed Nd:YAG laser-melted high-speed steel, namely HS6-5-2. The high chemical homogeneity and fine structure of the melted zone was attributed to high cooling rates due to the short duration of interaction with the Nd:YAG pulsed laser radiation and the relatively small volume of the melted material. The structure obtained in the surface layer after laser melting has a high level of hardness and shows improved wear resistance. [source] Isotactic polypropylene solidification under pressure and high cooling rates.POLYMER ENGINEERING & SCIENCE, Issue 11 2000A master curve approach Solidification in industrial processes very often involves flow fields, high thermal gradients and high pressures: the development of a model able to describe the polymer behavior becomes complex. Recently a new equipment has been developed and improved to study the crystallization of polymers when quenched under pressure. An experimental apparatus based on a modified, special injection moulding machine has been employed. Polymer samples can be cooled at a known cooling rate up to 100°C/s and under a constant pressure up to 40 MPa. Density, Micro Hardness (MH), Wide angle X-ray diffraction (WAXD), and annealing measurements were then used to characterize the obtained sample morphology. Results on one iPP sample display a lower density and a lower density dependence on cooling rate for increasing pressure. Micro hardness confirms the same trend. A deconvolution technique of WAXD patterns is used to evaluate the final phase content of samples and to assess a crystallization kinetics behavior. A master curve approach to explain iPP behavior under pressure and high cooling rates was successfully applied on density results. On the basis of this simple model it is possible to predict the final polymer density by superposition of the effect of cooling rate and the effect of pressure in a wide range of experimental conditions. [source] Do physical forces contribute to cryodamage?BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Joseph Saragusty Abstract To achieve the ultimate goal of both cryosurgery and cryopreservation, a thorough understanding of the processes responsible for cell and tissue damage is desired. The general belief is that cells are damaged primarily due to osmotic effects at slow cooling rates and intracellular ice formation at high cooling rates, together termed the "two factor theory." The present study deals with a third, largely ignored component,mechanical damage. Using pooled bull sperm cells as a model and directional freezing in large volumes, samples were frozen in the presence or absence of glass balls of three different diameters: 70,110, 250,500, and 1,000,1,250,µm, as a means of altering the surface area with which the cells come in contact. Post-thaw evaluation included motility at 0,h and after 3,h at 37°C, viability, acrosome integrity, and hypoosmotic swelling test. Interactions among glass balls, sperm cells, and ice crystals were observed by directional freezing cryomicroscopy. Intra-container pressure in relation to volume was also evaluated. The series of studies presented here indicate that the higher the surface area with which the cells come in contact, the greater the damage, possibly because the cells are squeezed between the ice crystals and the surface. We further demonstrate that with a decrease in volume, and thus increase in surface area-to-volume ratio, the intra-container pressure during freezing increases. It is suggested that large volume freezing, given that heat dissipation is solved, will inflict less cryodamage to the cells than the current practice of small volume freezing. Biotechnol. Bioeng. 2009; 104: 719,728 © 2009 Wiley Periodicals, Inc. [source] | ||||||||||