11 research outputs found
The effect of homogenization practice on the microstructure of AA6063 alloys
No full textHomogenization is an essential step in the preparation of aluminum billets for extrusion and is performed to produce a homogeneous solid solution and to transform the beta-AlFeSi particles to the finer and more equiaxed and thus more acceptable a variety. Homogenized billets require lower extrusion pressures and give extrusions with better surface finish and higher strength than as-cast billets. The extrudability of the billet is maximized once the solutionizing of the Mg2Si particles is optimized and the beta-->alpha transformation is complete. The latter takes higher temperatures and longer times and often requires help through revision of the alloy chemistry, i.e. addition of some Mn. The cooling practice in a homogenization treatment is just as significant as soaking and a variety of microstructures ranging from a fully solutionized homogeneous matrix to a heterogeneous one with a coarse dispersion of Mg2Si particles can be produced by simply adjusting the cooling rate. The optimum rate is that which gives Mg2Si precipitation readily redissolvable during subsequent processing and is dictated by the preheating, practice. The present work was undertaken to identify the optimum homogenization soaking and cooling practice for a semicontinous DC-cast AA6063 billet which, due to its composition (very low Mn), relies solely on the soaking practice for the beta-->alpha transformation
The performance of TiB, and TiC bearing grain refiners in twin roll strip casting
No full textThe master alloys based on the Al-Ti-b system have been used extensively for grain refining aluminum alloys. The TiB2 particles in commercial AlTiB master alloys, however, are rather coarse and have a tendency to agglomerate both during the manufacturing process and after being released into the melt, leading to a number of quality problems. These quality-related problems have created a big demand for an acceptable replacement for AlTiB master alloys. The Al-Ti-C system thus received particular attention as TiC has been assumed for a long time to be the nucleant for aluminum treated with hypo-peritectic Ti concentrations. TiC particles are claimed to be smaller than the TiB2 particles and are less prone to agglomeration. The Al-3%Ti-0.15%C alloy of this new generation grain refiners have been used commercially for several years in a wide range of alloy systems. Much of the work reported on this alloy, however, has been from laboratory scale testing while data on commercial applications is rather scarce. In the present work, coomercially available Al-3%Ti-0.15%C grain refiner was employed in the twin roll strip casting of the AA8111 alloy. Its grain refining potency was compared with that of the Al-5%Ti-0.2%B master alloy, the standard grain refiner in aluminium industry for the manufacture of aluminium fin and foil products
Production of 150 cm wide AZ31 magnesium sheet by twin roll casting
No full textKaya, Ali Arslan/0000-0002-4467-3456; Duygulu, Ozgur/0000-0001-8646-0363; Yucel, Onuralp/0000-0002-3879-0410; Duygulu, Ozgur/0000-0001-8646-0363WOS: 000262155200037150 cm wide AZ31 magnesium alloy sheet was produced by twin roll casting. The sheets of 6 mm thickness were cast. The sheet material was characterized using various techniques including metallography and XRD. The mechanical properties were investigated by tensile tests and hardness measurements. The procedures were developed for thermomechanical treatment of cast sheet material. The products of these procedures were characterized and the results were discussed for possible potential applications
Production of 150 cm wide AZ31 magnesium sheet by twin roll casting
No full text150 cm wide AZ31 magnesium alloy sheet was produced by twin roll casting. The sheets of 6 mm thickness were cast. The sheet material was characterized using various techniques including metallography and XRD. The mechanical properties were investigated by tensile tests and hardness measurements. The procedures were developed for thermomechanical treatment of cast sheet material. The products of these procedures were characterized and the results were discussed for possible potential applications
Direct Characterization of Transcription Elongation by RNA Polymerase I.
No full textRNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo
Development of 1500MM wide wrought magnesium alloys by twin roll casting technique in Turkey [Conference Paper]
No full textMagnesium Committee of the Light Metals Division; Minerals, Metals and Materials Society, TMSMagnesium Technology 2009, 15 February 2009 through 19 February 2009, San Francisco, CA, 76923Magnesium alloy AZ31, AZ61, AZ91, AM50 and AM60 sheets were produced by twin roll casting first time in Turkey. Sheets of 4.5-6.5mm thick and 1500mm width were successfully achieved. Microstructure of the sheet was analyzed by optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). Semi-quantitative analyses were performed by SEM-EDS. In addition, X-ray studies were performed for both characterization and texture purposes. Mechanical properties were investigated by tensile tests and also hardness measurements. Homogenization and annealing heat treatments were performed on the produced sheets
Development of 1500MM Wide Wrought Magnesium Alloys by Twin Roll Casting Technique in Turkey [Book Chapter]
No full textMagnesium alloy AZ31, AZ61, AZ91, AM50 and AM60 sheets were produced by twin roll casting first time in Turkey. Sheets of 4.5-6.5mm thick and 1500mm width were successfully achieved. Microstructure of the sheet was analyzed by optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). Semi-quantitative analyses were performed by SEM-EDS. In addition, X-ray studies were performed for both characterization and texture purposes. Mechanical properties were investigated by tensile tests and also hardness measurements. Homogenization and annealing heat treatments were performed on the produced sheets. © 2014 The Minerals, Metals & Materials Society
Development of rolling technology for twin roll casted 1500MM wide magnesium AZ31 alloy
No full textMagnesium Committee of the Light Metals Division; Minerals, Metals and Materials Society, TMSMagnesium Technology 2009, 15 February 2009 through 19 February 2009, San Francisco, CA, 76923Magnesium alloy AZ31 sheets of 4.5-6.5mm thick and 1500mm width were produced by twin roll strip casting first time in Turkey. Afterwards, sheets were hot and cold rolled down to less than 1mm both by laboratory and industrial scale rolls. Microstructure of the sheet was analyzed by optical microscope and transmission electron microscope. In addition, pole figures have been obtained by XRD studies. Mechanical properties were investigated by tensile tests and also hardness measurements. Annealing heat treatments were performed on the produced sheets
Pol I elongation rates.
No full textThe average rate (a) was calculated from the beginning to the end of each elongation run. The maximum rate (b) in each of the 65 traces was found as described in the Materials and Methods, “Particle Tracking and Transcription Rate Analysis.” The distributions of (a) and (b) were then fitted with exponential functions with mean values of 20.7 (average) and 58.4 (maximum) nt/s rates of elongation (R-values of 0.95 and 0.98 respectively). These mean values are significantly different with respective 95% confidence intervals of (14.1–27.3) and (48.6–68.4) relative to the fitted mean values. Note that for an exponential distribution, the standard deviation is equal to the mean.</p
