The increasing demand for reducing vehicle weight in the automotive and aerospace industries has raised the need to develop improved structural aluminum-based alloys. Thus, horizontal solidification experiment with the Al-7%Si-0.3%Mg (mass fraction) alloy was carried out. A water-cooled horizontal directional solidification device was developed and used. Microstructural characterization was carried out using traditional techniques of metallography, optical microscopy and SEM microscopy. The Thermo-Calc software was used to generate the solidification path of the investigated alloy with addition of 0.17% Fe (mass fraction). The effects of the thermal parameters such as the growth rate (VL), cooling rate (TC) and solidification local time (tSL) on the formation of the macrostructure and on the dendritic microstructure evolution were evaluated. A columnar to equiaxed transition (CET) was found for VL and TC values from 0.82 to 0.98 mm/s and from 1.71 to 2.55 °C/s, respectively. The microstructure was characterized by the measurement of the primary and secondary dendrite arm spacings (λ1 and λ2, respectively). Experimental laws of λ1 =f(VL, TC) and λ2 =f(tSL) were proposed. It is observed that the interdendritic region is composed of the following eutectic mixture: α(Al)+Si+π-Al8Mg3FeSi6+θ-Mg2Si. 相似文献
Pearlite interlamellar spacing is an important parameter controlling ductility and strain hardening of carbon steels. Fine
pearlite is the appropriate initial microstructure for drawing high carbon steel with exponential strain hardening rate, leading
to high final tensile strengths. The majority of optical and electron microscopy methods for measuring interlamellar spacing
present difficulties when applied to fine microstructures. Atomic force microscopy (AFM) was employed to investigate pearlitic
steels lead patented at 510 °C and then cold drawn to 86% reduction in area. Conventional specimen preparation techniques
for optical metallography were appropriated to produce high resolution AFM images, on which measurements of minimum interlamellar
spacing, in good agreement with spacings estimated using the Embury–Fisher model, were easily performed.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
An Instron Universal testing machine and Differential Scanning Calorimetry were used to investigate textural changes in cooked rice during storage. Two cells were used with the Instron for hardness measurement (Ottawa Texture Measuring System and Back Extrusion cells) and one cell for adhesion measurement (adhesion cell). During storage of cooked rice, retrogradation of the starch led to an increase in hardness as well as a decrease in the adhesion of cooked rice. Storage time, temperature and variety significantly influenced the hardness and adhesion of cooked rice. A correlation analysis between methods showed that Instron measurements OTMS and BE correlated better with a correlation coefficient of 0.978 than the two Instron methods and DSC with a correlation coefficient of 0.752. 相似文献
One of the major difficulties in interlaminar fracture tests of multidirectional laminates is the high tendency for intralaminar cracking and the resulting wavy crack propagation. Experimental work showed that this occurred in double cantilever beam (DCB) tests of cross‐ply laminates having a starter crack on a 0°/90° interface. Moreover, under steady‐state propagation conditions, the apparent values of the critical strain energy release rate GIc were two times higher than those of 0°/0° specimens. In this paper, a finite‐element‐based progressive damage model was used to simulate crack propagation in cross‐ply specimens. The results showed that transverse cracking alone cannot be responsible for the above difference of GIc values. Therefore, the higher propagation GIc values for cross‐plies must be attributed to the more extensive fibre bridging observed and to plastic deformations of the 90° interfacial ply. 相似文献
We report a new and efficient methodology of labelling red blood cells, in order to investigate the expression of anti-A antigen, employing luminescent semiconductor nanocrystals. Highly luminescent and stable core-shell cadmium sulphide/cadmium hydroxide [CdS/CdS(OH)2] colloidal particles were obtained in the nanometre size range. The surface of these particles was characterized by using a monoclonal anti-A antibody via a one-step glutaraldehyde cross-linking procedure, followed by conjugation of the particles to red cells of blood groups A+, and O+. Laser scanning confocal microscopy images indicated that after conjugation for 30 min, A+ and erythrocytes presented different patterns of dual bright emission whereas the O+ group cells showed no emission. We suggest that this labelling procedure may be applied as a quantitative tool to investigate the distribution and expression of alloantigen in red blood cells. 相似文献
Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady‐state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. 相似文献
The roots of the vegetal Curcuma due to its high content of polyphenols, has been used successfully in several clinical situations. This review assessed the effect of curcumin/Curcuma longa on symptoms and metabolic changes in inflammatory bowel disease (IBD). A systematic review of animal models and randomized clinical trials (RCTs) was conducted by searching the following electronic databases: PubMed, CENTRAL, LILACS, Science Direct, and ClinicalTrials.gov. From 997 found records, 62 were included. More than 90% of the animal studies reported an improvement in macroscopic, histologic and/or functional activity; 80% identified decreased oxidative and/or inflammatory biomarkers in animals treated with curcumin. Among the RCTs, intention-to-treat analysis showed that oral curcumin was effective in inducing clinical remission (n = 281, RR: 3.15 CI 95% [1.22–8.10] p = 0.0017; i² = 72.2%, p = 0.006) and clinical response (n = 259, RR: 1.60 CI 95% [1.09–2.35] p = 0.0017; i² = 59.7%, p = 0.042) but not endoscopic remission (n = 161, RR: 2.91 CI 95% [0.58–14.58] p = 0.195; i² = 72.7%, p = 0.026). These results confirm that oral supplementation with curcumin/Curcuma longa has beneficial actions in animal colitis and, when associated with drug therapy, is effective in the treatment of patients with IBD.
A restructured potato model system was fried for 5, 10 or 15 min at 170, 180, or 190C and tested in a dynamic mechanical analyzer. Stress relaxation phenomena was described by a two‐element Maxwell model with a parallel spring. The viscoelastic behavior of the crust resulted from its porous structure of open and closed foam cells embedded in oil. Relaxation of stress in the fried crust was a result of slippage of the dispersed oil through the crust and from rearrangements of the air cells. Elastic modulus of the fried crust increased for higher frying times and temperatures and were the most significant elements in distinguishing between samples. 相似文献