890 resultados para HEAT-TREATMENT
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Adding 1%Si to binary Al-5Mg alloy slightly increases the yield stress in comparison with the Si free alloy but dramatically reduces the ductility and tensile strength due to the formation of brittle eutectic Mg2Si and pi-Al8FeMg3Si6 particles. Adding 3%Si slightly reduces the yield stress, presumably due to some of the Mg being tied up in the Mg2Si, and further reduces the ductility due to the increased volume fraction of intermetallics. Solution heat treatment at 436degreesC decreases the yield stress of both Si containing alloys, and slightly increases the ductility in the alloy with 3%Si. Subsequent ageing at 180degreesC has no further effects on the strength or ductility. The loss in strength of the heat treated alloys seems to be due to overageing Of Mg2Si precipitates dispersed in the bulk of the alloy. (C) 2004 W. S. Maney Son Ltd.
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The effectiveness of rapid and controlled heating of intact tissue to inactivate native enzymatic activity and prevent proteome degradation has been evaluated. Mouse brains were bisected immediately following excision, with one hemisphere being heat treated followed by snap freezing in liquid nitrogen while the other hemisphere was snap frozen immediately. Sections were cut by cryostatic microtome and analyzed by MALDI-MS imaging and minimal label 2-D DIGE, to monitor time-dependent relative changes in intensities of protein and peptide signals. Analysis by MALDI-MS imaging demonstrated that the relative intensities of markers varied across a time course (0-5 min) when the tissues were not stabilized by heat treatment. However, the same markers were seen to be stabilized when the tissues were heat treated before snap freezing. Intensity profiles for proteins indicative of both degradation and stabilization were generated when samples of treated and nontreated tissues were analyzed by 2-D DIGE, with protein extracted before and after a 10-min warming of samples. Thus, heat treatment of tissues at the time of excision is shown to prevent subsequent uncontrolled degradation of tissues at the proteomic level before any quantitative analysis, and to be compatible with downstream proteomic analysis.
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Pulsed Nd:YAG has been adopted successfully in welding process of thin (0.7 mm) Ti6Al4V. Laser welding of such thin sheet requires a small focal spot, good laser beam quality and fast travel speed, since too much heat generation can cause distortion for thin sheet weld. The microstructures of Ti6Al4V were complex and strongly affected the mechanical properties. These structures include: a´ martensite, metastable ß, Widmanstätten, bimodal, lamellar and equiaxed microstructure. Bimodal and Widmanstätten structures exhibit a good-balance between strength and ductility. The microstructure of pulsed Nd:YAG welded Ti6Al4V was primarily a´ martensite, which showed the lowest ductility but not significantly high strength. A heat treatment at 950 followed by furnace cooling can transform the microstructure in the weld from a´ martensite structure into Widmanstätten structure.
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The fatigue-crack propagation and threshold behaviour of a C-Mn steel containing boron has been investigated at a range of strength levels suitable for mining chain applications. The heat-treatment variables examined include two austenitizing temperatures (900 degree C and 1250 degree C) and a range of tempering treatments from the as-quenched condition to tempering at 400 degree C. In mining applications the haulage chains undergo a 'calibration' process which has the effect of imposing a tensile prestrain on the chain links before they go into service. Prestrain is shown to reduce threshold values in these steels and this behaviour is related to its effects on the residual stress distribution in the test specimens.
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The reuse of industrial by-products is important for members of numerous industrial sectors. However, though the benefits of reuse are evident from an economical point of view, some compounds in these materials can have a negative effect on users' health.In this study, the radon emanation and exhalation features of red mud were surveyed using heat-treatment (100-1200 °C). As a result of the 1200°C-treated samples, massic radon exhalation capacity reduced from 75 ± 10 mBq kg-1 h-1 to 7 ± 4 mBq kg-1 h-1, approximately 10% of the initial exhalation rate.To find an explanation for internal structural changes, the porosity features of the heat-treated samples were also investigated. It was found that the cumulative pore volume reduced significantly in less than 100 nm, which can explain the reduced massic exhalation capacity in the high temperature treated range mentioned above.SEM snapshots were taken of the surfaces of the samples as visual evidence for superficial morphological changes. It was found that the surface of the high temperature treated samples had changed, proving the decrement of open pores on the surface.