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Effect of P/M value on the preforms and microstructures of spray formed 70Si30A1 alloy
Abstract
A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate (PIM) on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209–0.231 MPa/(kg-min-1). The microstructure of the spray formed 70Si30Al alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into wo groups: supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.
... The family of the studied spray-deposited Si-Al are made by atomization by Sandvik Osprey™. The major influencing parameters of the process of atomization [11] (for example: pressure during hot compression step to decrease the porosity [12] and Gas/metal mass flow ratio [13]) were evidenced and analysed to obtain the desired specific microstructure and the corresponding material properties. The specific two-phase microstructure of spray deposited hypereutectic Si-Al alloys was studied as well [14] [15]. ...
... In this case, both stress components follow Eq. (12) and the integration of Eq. (7) over the whole part thickness results in Eq. (13). ...
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The spray-deposited Si–Al CE9F alloy is a new material used for space applications involving temperature gradient. Thermal stresses arise and may affect the mechanical integrity of the components. It is therefore necessary to assess the critical temperature gradient to avoid failure. Hence this paper deals with the effect of temperature on the mechanical properties of the Si–Al CE9F alloy from − 50 °C to 130 °C: Young's modulus, coefficient of thermal expansion and Weibull's parameters of the material to account for its brittle fracture behaviour through the Weibull's model. The experiments indicate a linear dependence of the Young's modulus with temperature and show that the coefficient of thermal expansion and the Weibull's parameters are almost constant in the temperature range [− 50 °C, 130 °C]. From these results, an example of application schematizing a clamped plate under temperature gradient is studied to create abacus of probability of failure. These abacuses provide sizing guidelines and show the impact of the equivalent volume, highlighting the critical temperature gradients.
This paper investigates the effects of temperature cycles between −55 °C and 125 °C (the temperature range for intended space application) on the strength and microstructure of spray deposited Si–Al CE9F alloy. After 500 cycles, the strength is significantly improved of 9% (i.e., 26 MPa). Moreover the Weibull modulus also undergoes a significant increase. Microstructure characterizations by XRD, SEM, EBSD and DSC evidence recovery and recrystallization processes in the Al phase, and subgrain development at grain boundaries in the Si phase, leading to lower crystallite size. A Hall–Petch dependence of mean strength to average crystallite size in Si is proposed as strengthening mechanism.
In the present investigation, a very good combination of strength and ductility, 630 MPa 0.2% proof stress and 14.8% elongation to fracture in tensile test, has been obtained for the 7075 Al alloy after optimizing the processing parameters for spray forming, hot extruding the spray deposit, and peak aging the samples taken from the extruded rod. The spray deposits contained some porosity but it was almost eliminated on hot extrusion. Electron probe microanalysis revealed that even though spray forming was carried out in an open atmosphere, it did not affect the oxygen content and its distribution in the material on spray forming, because the atomizing argon gas provided a protective cover to molten droplets and prevented their oxidation. The chemical composition of the spray-formed material was found to be almost the same as the raw material, and the major alloying elements were found to be uniformly distributed in the extruded rod.
The grain growth behavior of melt in-situ reaction spray deposited 7075+TiC (2.91%, voluminal fraction) alloy were studied, and the effect of in-situ TiC particles on the microstructure of spray-formed 7075 alloy was investigated. The sectioned specimens were heat-treated isothermally at various temperatures between the solidus and liquidus of 7075 alloy for times in the range of 10-60 min, then quenched in water. The microstructure of reheated specimens was characterized using SEM and the grain size was measured using a mean linear intercept method. It is shown that the in-situ TiC particles can effectively control grain size even at 600°C after 60 min.
70%Si-Al alloy as a novel electronics package material was prepared by spray deposition. HIP technique was adopted in order to density the billet. The prepared 70%Si-Al alloy has a microstructure with fine silicon particles (10-20 μm in diameter) well dispersed in the matrix. The alloy shows excellent comprehensive properties, especially a lower thermal expansion coefficient and a lower density compared with the traditional electronics packaging materials. After HIP, The comprehensive properties of the 70%Si-Al alloy can be further enhanced. The alloy can be machined with the traditional cutting tools and applied as the packaging materials for the power IC, microwave electronic parts and integrate circuit blocks.
The effect of ratio of the atomization pressure to the melt mass flux rate(p/m) on the preforms of spray formed 70Si30Al alloy was studied. The results indicate that ratio of the atomization pressure to the melt mass flux rate has considerate influence on the yield of the preforms, dimension of the primary silicon phases and the relative density, which decrease with ratio of p/m increasing. Effect of p/m ratio on the yield of the preforms, dimension of the primary silicon phases and the relative density is comprehensively considered, then the optimal ratio of p/m is 0.209-0.231 MPa/(kg · min-1).
A novel 70Si30Al alloy was prepared by spray forming process for electronic packaging material. Micro-structure variation of as-deposited preforms during heating procedure was studied. The results show that the micro-structure is fine and homogenous, the primary silicon phases distributing in the alloy evenly are fine and irregular, and most of the phases that disperse between the primary silicon phases are supersaturated α(Al) and Al-Si Pseudo-eutectic phases. When the alloy is held under 620°C for 90 min, the primary silicon phases do not increase obviously and have spheroidized phenomenon with temperature increasing. The supersaturated α(Al) phases do not change significantly during heating procedure. The Al-Si pseudo-eutectic phases remelt in the temperature range from 566°C to 582°C, and the mass of remelting phases increase with temperature increasing and they conglomerate together. The range of hot deformation temperature of spray formed 70Si30Al alloy is from 560°C to 590°C.
A new family of spray formed SI-AI alloys has been developed for electronic applications. Their physical characteristics, combining low thermal expansivity, high thermal conductivity, and low density, make them attractive for packaging of avionics, including rf and microwave circuitry, These alloys are easy to machine to tight tolerances and can be electroplated with gold, silver, or nickel finishes. Being non-toxic, they do not require any special handling. Microwave amplifier modules designed for space applications, providing weight savings of 30% over conventional packages, have been successfully produced and tested.
We present an ab initio direct dynamics study of thermal rate constants of the hydrogen abstraction reaction of C2H3 + HCHO → C2H4 + CHO. The MP2/cc-pVDZ method is employed to optimize the geometries of stationary points as well as the points on the minimum energy path (MEP). The energies of all the points were further refined at the QCISD(T)/cc-pVTZ level of theory. The rate constants were evaluated using canonical variational transition state theory (CVT) and canonical variational transition state theory with small-curvature tunneling contributions (CVT/SCT) in the temperature range of 300–2500 K. The calculated results show that the rate constants have positive temperature dependence in the calculated temperature range. The calculated rate constants at the QCISD(T)/cc-pVTZ//MP2/cc-pVDZ level of theory are in good agreement with available literature data.
The set of properties required for microwave packaging materials intended for aerospace applications is discussed in relation to the current range of materials that are commercially available. Initiatives are being taken to replace kovar, the established packaging material, with substitutes which are lighter, stiffer and offer superior heat-sinking. Promising in this regard are new family of beryllium-beryllia and also silicon-aluminium (Si-Al) alloys high in silicon, with ratios of constituents chosen such that they optimally complement gallium arsenide MMIC devices and alumina circuit boards. Both types of material are relatively easy to machine and electroplate. Demonstrator microwave amplifier modules incorporating the Si-Al alloys have been designed for space applications and have been successfully produced and tested. The manufacturing technology that has been developed for this purpose is described.
At present, the spectral model is one of the most widely applied numerical models in the research of numerical prediction
and climatic variation. To improve the precision and efficiency of spectral method can greatly contribute to the development
of numerical prediction. As the core part of spectral method, the calculating method of nonlinear terms always concentrates
on numerical solution of atmospheric dynamical processes in the spectral space. However, there was little study in this field
in the late thirty years. According to the principle of nonlinear term calculation with the dimensionality degradation and
latitudinal perfect spectral method, we designed a new nonlinear term calculating method and made it compatible well with
the common numerical algorithms of the spectral model used internationally. With an own-designed spectral dynamical framework
suiting for the numerical application in common uses, theoretical analyses and numerical experiments have also been deeply
conducted to compare our new method with the widely-used transform method in an attempt to advance the development of numerical
algorithms of spectral model.
Keywordsspectral model-dynamical framework-nonlinear term-spectral method
Let be a set of line segments in three dimensional Euclidean space. In this paper, we prove several characterizations of tetrahedralizations. We present an O(mnlogn) algorithm to determine whether is the edge set of a tetrahedralization, where m is the number of segments and n is the number of distinct endpoints of segments in . We show that it is NP-complete to decide whether contains the edge set of a tetrahedralization. We also show that it is NP-complete to decide whether is a subset of the edge set of a tetrahedralization.
Life Cycle Cost (LCC) is a very important issue for organizations, which determines the success of their businesses. However, information gather- ing from a highly distributed heterogeneous environment with a huge number of information sources is an obstacle to the use of the existing LCC models. To overcome this obstacle, we took an agent-based information gathering system as a solution. In order to develop an agent-based system in a systematic way, we established a m ethodology of agent-oriented system engineering. Therefore, the system development follows a step by step process from the stage of system requirement to implementation. This paper presents this methodology and illus- trates the processes of system analysis, design, and implementation by appl y- ing this methodology to information gathering for the CASA (Cost Analysis Strategy Assessment) model. The experimental results show that the agent technology is useful and beneficial for LCC information gathering.
hTid-1, a human homolog of the Drosophila tumor suppressor l(2)Tid and a novel DnaJ protein, regulates the activity of nuclear factor kappaB (NF-kappaB), but its mechanism is not established. We report here that hTid-1 strongly associated with the cytoplasmic protein complex of NF-kappaB-IkappaB through direct interaction with IkappaBalpha/beta and the IKKalpha/beta subunits of the IkappaB kinase complex. These interactions resulted in suppression of the IKK activity in a J-domain-dependent fashion and led to the cytoplasmic retention and enhanced stability of IkappaB. Overexpression of hTid-1 by using recombinant baculovirus or adenovirus led to inhibition of cell proliferation and induction of apoptosis of human osteosarcoma cells regardless of the p53 expression status. Adherent cultured cells transduced with Ad.hTid-1 detached from the dish surface. Morphological changes consistent with apoptosis and cell death were evident 48 h after Ad.EGFP-hTid-1 transduction. In contrast, cells transduced with Ad.EGFP or Ad.EGFP-hTd-1DeltaN100, a mutant that has the N-terminal J domain deletion and that lost suppressive activity on IKK, continued to proliferate. Similar data were obtained with A375 human melanoma cells. Ad.EGFP or Ad.EGFP-hTd-1DeltaN100 ex vivo-transduced A375 cells injected subcutaneously into nude mice produced growing tumors, whereas Ad.EGFP-hTid-1-transduced cells did not. Collectively, the data suggest that hTid-1 represses the activity of NF-kappaB through physical and functional interactions with the IKK complex and IkappaB and, in doing so, it modulates cell growth and death.
As part of a four-year BRITE/EURAM collaborative project supported by the European Commission, a new family of low-expansion alloys based on aluminium-silicon has been developed; and the Hirst Division of GEC-Marconi Materials Technology is establishing procedures for fabricating packages for microwave unusually low density of these materials. They are also readily machinable and can be electroplated with relative ease, in sharp contrast with silicon carbide containing metal matrix composites and copper-tungsten. These characteristics make the new materials particularly suitable for short runs of homogeneous packages and carriers to particular designs, facilitated by the ability to insert hermetic feedthroughs and lid-seal. It has also been demonstrated that high integrity heterogeneous packages with kovar side-walls can be made, utilizing Hirst's unique diffusion soldering process for bonding the kovar and aluminium-silicon components together.
The ability to give higher priority to regions-of-interest (ROI) is the emerging functionality for present day video coding. A simple and fast method for face detection is proposed to define ROIs dynamically in real time applications. We use the color information Cr and RGB variance to determine the skin-color pixels. Because the two color spaces are commonly used in most hardware and video codec standards, there is no extra computation overhead required for conversion. Low-pass filtering is applied to the background to reduce used bits. For the video coding system, a region-based video codec based on H.263+ with the option mode of modified quantization is set up. We adjust the distortion weight parameter and variance at the macroblock layer to control the qualities at different regions. Experimental results show that the proposed methods can significantly improve quality at the ROI. Our methods are suitable for real time videoconferencing.
Present state and development of electronic packaging materials
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