فهرست مقالات microstructural characteristics

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  1 - Effects of Welding Cycles on Microstructural Characteristics and Mechanical Properties of SAF 2507 Super Duplex Stainless Steel
  M. A. Beheshty E. H. Dehkordi K. Zarrin Naghsh M. R. B. Marnany
  Unique characteristics of SAF 2507 (UNS S32750) super duplex stainless steels alloy such as its high mechanical properties and strong corrosion resistivity behavior led to its widely applications in sea water and other highly corrosive media in oil & gas industries, چکیده کامل

  Unique characteristics of SAF 2507 (UNS S32750) super duplex stainless steels alloy such as its high mechanical properties and strong corrosion resistivity behavior led to its widely applications in sea water and other highly corrosive media in oil & gas industries, however, its known that it has also got its own drawbacks particularly the impact and consequences that the number of heating/cooling cycles during its welding or welding repairs may have on its functional characteristics. While international standards/codes are not defining any limitation on weld repairs and/or permitted numbers of weld repairs on duplex stainless steel materials, some owners and clients are limiting the number of permitted repairs to maximum two (just to be in safe side) hence always motivating the question if the number of repairs become more than two, whether and how that could affect the microstructural characteristics and mechanical properties of a welded duplex material. This subject has also never been discussed in any of the earlier investigations. The current proposed article scrutinizing the effect of number of welding repairs on functional characteristics of an SAF 2507 welded plate. 4 samples have been welded by GTAW process using rod ER2594 filler metal with 0 to 3 numbers of repairs on them to evaluate the effect of various numbers of heating/cooling cycles caused by different numbers of repairs on the weldment. Mechanical properties and microstructural characteristics of the samples have been analyzed to observe the excessive presence of any detrimental intermetallic phases and also to see whether any changes in the value of mechanical properties have been occurred or not. It has been concluded that the number of weld repairs (up to 3 times as been examined here and even higher) on welded samples has got no (negligible) negative impacts on the strength of weldments or other mechanical / microstructural characteristics of the weldment, if done properly. پرونده مقاله
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  2 - Effect of Silicon Carbide and graphite additives on the pressureless Sintering mechanism and microstructural characteristics of Ultra-High Temperature ZrB2 Ceramics Composites
  Mahdi Khoeini Mohammad Zakeri Ali Nemati Morteza Tamizifar Hamed Samadi
  The effect of SiC content, additives, and process parameters on densification and microstructural properties of pressureless sintered ZrB2– (1–10 wt %) SiC particulate composites have been studied. The ZrB2–SiC composite powders mixed by Spex mixer wit چکیده کامل

  The effect of SiC content, additives, and process parameters on densification and microstructural properties of pressureless sintered ZrB2– (1–10 wt %) SiC particulate composites have been studied. The ZrB2–SiC composite powders mixed by Spex mixer with 1-2wt% C (added as graphite powder) and CMC have been cold-compacted and sintered in argon environment in the temperature range of 1800–2100ºC for 2hs. The amount of densification is found to increase with sintering duration and by prior holding at 1200-1650ºC for reduction of oxide impurities (ZrO2, B2O3 and SiO2) on powder particle surfaces via the formation of new phases such as ZrSi2 and ZrC in the system. Presence of SiC with average size smaller than that of ZrB2 appears to aid in densification by enhancing green density, increasing C content by erosion of milling media, and inhibiting matrix grain growth. Both of SiC and C appear to aid in reduction of oxide impurities. The shrinkage of samples was measured, and the microstructure of samples was examined using X-Ray Diffraction and scanning electron microscopy (SEM), equipped with EDS spectroscopy. Room temperature mechanical properties were examined. Sintering temperature has a great effect on relative density, porosity, water absorption, hardness, fracture toughness, oxidation resistance, Strength and microstructure of these composites. The highest relative density, (99.65%), was obtained in ZrB2–10wt. %SiC–2 wt. %C composites sintered at 2000ºC for 2hs. پرونده مقاله