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M. Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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development of al ti c grain Refiners and study of their grain refining efficiency on al and al 7si alloy
Journal of Alloys and Compounds, 2005Co-Authors: G Vinod S Kumar, B.s. Murty, M. ChakrabortyAbstract:Abstract Al–5Ti–0.8C and Al–5Ti–1.2C master alloys have been successfully prepared by reaction of K2TiF6 salt and graphite powder with molten Al. While the Al–5Ti–0.8C consists of some TiAl3 particles in addition to TiC particles in the Al matrix, the Al–5Ti–1.2C master alloy revealed the presence of only TiC particles. The grain refining efficiency of these two master alloys has been compared with that of the conventional Al–5Ti–1B master alloy on Al and Al–7Si alloy at different addition levels. Al–5Ti–1.2C master alloy was found to be the most efficient grain refiner for Al amongst the grain Refiners studied. Even in case of Al–7Si alloy, the Al–5Ti–0.8C and Al–5Ti–1.2C master alloys performed better than conventional Al–5Ti–1B master alloy. However, the Al–5Ti–1.2C master alloy shows poor response to grain refinement in Al–7Si alloy at higher addition levels than the Al–5Ti–0.8C master alloy, indicating poisoning.
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Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying
International Materials Reviews, 2002Co-Authors: B.s. Murty, S. A. Kori, M. ChakrabortyAbstract:Grain refinement of aluminium and its alloys is common industrial practice. The field has been extensively investigated by many workers over the past 50 years, not only to develop efficient grain Refiners for different aluminium alloys, but also to achieve an understanding of the mechanism of grain refinement. The present review confines itself to the literature on grain refinement by heterogeneous nucleation and alloying. Initially, the fundamentals of grain refinement by inoculants are outlined. The types of grain refiner, Al-Ti-B master alloys in particular, and their methods of manufacture are next discussed. The grain refining tests to assess the efficiency of the grain Refiners and the grain refining behaviour of aluminium alloys are also discussed in brief. The performance of a grain refiner, as well as the response of an aluminium alloy to grain refinement, is influenced by the microstructure of the grain refiner as controlled by the process parameters involved in its preparation and the alloying elements present in the aluminium alloy. The roles of these factors, and particularly the roles of poisoning elements such as Si, Cr, Zr, Li, are reviewed. The paper also reviews the mechanisms of grain refinement, the fading and poisoning phenomena, and the trends in the development of new grain Refiners for aluminium alloys containing poisoning elements.
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development of an efficient grain refiner for al 7si alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: S. A. Kori, B.s. Murty, M. ChakrabortyAbstract:Abstract The response of Al–7Si alloy towards grain refinement by Al–Ti–B master alloys (with different Ti–B ratios) at different addition levels has been studied in detail. The results indicate that high B-containing master alloys are powerful grain Refiners when compared to conventional grain Refiners like Al–5Ti–lB master alloys. In the present study, indigenously developed master alloys have been used for the grain refinement of alloys Al–7Si and LM-25 . Significant improvements in mechanical properties have been obtained with a combination of grain refiner and Sr as modifier.
B.s. Murty - One of the best experts on this subject based on the ideXlab platform.
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development of al ti c grain Refiners and study of their grain refining efficiency on al and al 7si alloy
Journal of Alloys and Compounds, 2005Co-Authors: G Vinod S Kumar, B.s. Murty, M. ChakrabortyAbstract:Abstract Al–5Ti–0.8C and Al–5Ti–1.2C master alloys have been successfully prepared by reaction of K2TiF6 salt and graphite powder with molten Al. While the Al–5Ti–0.8C consists of some TiAl3 particles in addition to TiC particles in the Al matrix, the Al–5Ti–1.2C master alloy revealed the presence of only TiC particles. The grain refining efficiency of these two master alloys has been compared with that of the conventional Al–5Ti–1B master alloy on Al and Al–7Si alloy at different addition levels. Al–5Ti–1.2C master alloy was found to be the most efficient grain refiner for Al amongst the grain Refiners studied. Even in case of Al–7Si alloy, the Al–5Ti–0.8C and Al–5Ti–1.2C master alloys performed better than conventional Al–5Ti–1B master alloy. However, the Al–5Ti–1.2C master alloy shows poor response to grain refinement in Al–7Si alloy at higher addition levels than the Al–5Ti–0.8C master alloy, indicating poisoning.
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Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying
International Materials Reviews, 2002Co-Authors: B.s. Murty, S. A. Kori, M. ChakrabortyAbstract:Grain refinement of aluminium and its alloys is common industrial practice. The field has been extensively investigated by many workers over the past 50 years, not only to develop efficient grain Refiners for different aluminium alloys, but also to achieve an understanding of the mechanism of grain refinement. The present review confines itself to the literature on grain refinement by heterogeneous nucleation and alloying. Initially, the fundamentals of grain refinement by inoculants are outlined. The types of grain refiner, Al-Ti-B master alloys in particular, and their methods of manufacture are next discussed. The grain refining tests to assess the efficiency of the grain Refiners and the grain refining behaviour of aluminium alloys are also discussed in brief. The performance of a grain refiner, as well as the response of an aluminium alloy to grain refinement, is influenced by the microstructure of the grain refiner as controlled by the process parameters involved in its preparation and the alloying elements present in the aluminium alloy. The roles of these factors, and particularly the roles of poisoning elements such as Si, Cr, Zr, Li, are reviewed. The paper also reviews the mechanisms of grain refinement, the fading and poisoning phenomena, and the trends in the development of new grain Refiners for aluminium alloys containing poisoning elements.
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development of an efficient grain refiner for al 7si alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: S. A. Kori, B.s. Murty, M. ChakrabortyAbstract:Abstract The response of Al–7Si alloy towards grain refinement by Al–Ti–B master alloys (with different Ti–B ratios) at different addition levels has been studied in detail. The results indicate that high B-containing master alloys are powerful grain Refiners when compared to conventional grain Refiners like Al–5Ti–lB master alloys. In the present study, indigenously developed master alloys have been used for the grain refinement of alloys Al–7Si and LM-25 . Significant improvements in mechanical properties have been obtained with a combination of grain refiner and Sr as modifier.
Yucel Birol - One of the best experts on this subject based on the ideXlab platform.
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performance of al 5ti 1b and al 3b grain Refiners in investment casting of alsi7mg0 3 alloy with preheated ceramic moulds
International Journal of Cast Metals Research, 2012Co-Authors: Yucel BirolAbstract:AbstractThe performances of Al–5Ti–1B and Al–3B grain Refiners were investigated when casting AlSi7Mg0··3 alloy into preheated ceramic shell moulds. The former is a poor grain refiner when casting into shell moulds preheated to 300°C. The grains of the Ti free AlSi7Mg0··3 inoculated with the Al–3B alloy, on the other hand, are very fine, uniform and nearly globular, implying a remarkable grain refining efficiency. The average grain size 2 min after grain refiner addition is 190±16 μm, evidencing over a 10-fold refinement with respect to the unrefined sample. However, grain refining with the Al–3B alloy requires precise control of the Ti concentration in the melt. The Ti level must be kept below 70 ppm, preferably below 50 ppm, to ensure an adequate refinement effect. The cooling rate correlates with the dendrite arm spacing but fails to predict the grain size. An order of magnitude difference in grain size is noted in two samples solidified under exactly the same cooling rate and thus with nearly identica...
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alb3 master alloy to grain refine alsi10mg and alsi12cu aluminium foundry alloys
Journal of Alloys and Compounds, 2012Co-Authors: Yucel BirolAbstract:Abstract The potential of AlB3 master alloy in the grain refinement of AlSi10Mg and AlSi12Cu foundry alloys was investigated and compared with that of the AlTi5B1 master alloy, the standard grain refiner for most aluminium foundries. The latter refines the grain structures of both alloys. However, this performance is not nearly as good as that obtained in wrought aluminium alloys with the same grain refiner. The Ti-free AlSi10Mg and AlSi12Cu alloys, on the other hand, exhibit very small grains for the entire range of holding times when inoculated with AlB3. This implies a remarkable grain refining efficiency, typical of grain refined wrought aluminium alloys, as well as a strong resistance to fading of the grain refinement effect. Lack of Ti in the melt allows the entire B to form AlB 2 particles, the perfect substrates, shortly before α-Al starts to crystallize. Aluminium castings can enjoy grains as small as those of the wrought alloys, well below 200 μm, with an addition of 0.02 wt% B provided that their Ti content is controlled.
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The performance of Al-Ti-C grain Refiners in twin-roll casting of aluminium foilstock
Journal of Alloys and Compounds, 2006Co-Authors: Yucel BirolAbstract:The master alloys based on the Al–Ti–B system have been used extensively for refining the grain structure of aluminum alloys. The quality-related problems linked with the TiB2 particles, however, have generated an interest in the Al–Ti–C grain Refiners as an acceptable replacement for Al–Ti–B master alloys. TiC particles are smaller than the TiB2 particles and are less prone to agglomeration. Al–3Ti–0.15C grain Refiners have been in use for some time in several alloy systems. Much of the work reported on this alloy, however, has been from DC casting while performance data in strip casting is not available. In the present work, a commercial Al–3Ti–0.15C grain refiner was employed in the twin-roll casting of AA8111 foilstock. Its grain refining efficiency was compared with that of the Al–5Ti–0.2B master alloy, the standard grain refiner in aluminium industry for the manufacture of aluminium foil products.
A.l. Greer - One of the best experts on this subject based on the ideXlab platform.
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design of grain Refiners for aluminium alloys
erl3, 2016Co-Authors: A Tronche, A.l. GreerAbstract:The efficiency of a grain refiner can be quantified as the number of grains per nucleant particle in the solidified product. Even for effective Refiners in aluminium, such as Al-5Ti-1B, it is known from experiments that efficiencies are very low, at best 10-3 to 102. It is of interest to explore the reasons for such low values, and to assess the prospects for increased efficiency though design of Refiners. Recently it has been shown [1] that a simple recalescence-based model can make quantitative predictions of grain size as a function of refiner addition level, cooling rate and solute content. In the model, the initiation of grains is limited by the free growth from nucleant particles, the size distribution of which is very important. The present work uses this model as the basis for discussing the effect of particle size distribution on grain refiner performance. Larger particles (of TiB2 in the case of present interest) promote greater efficiency, as do narrower size distributions. It is shown that even if the size distribution could be exactly specified, compromises would have to be made to balance efficiency (defined as above) with other desirable characteristics of a refiner.
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modelling of the effectiveness of al ti b Refiners in commercial purity aluminium
Essential Readings in Light Metals Volume 3: Cast Shop for Aluminum Production, 2016Co-Authors: A M Bunn, P V Evans, D J Bristow, A.l. GreerAbstract:Al-5Ti-1B (wt.%) alloys are effective grain Refiners for DC-cast aluminium although as few as 1% of the TiB2 particles added to the melt nucleate grains. The aim of this work is to develop quantitative modelling for prediction of grain sizes in commercial purity aluminium. In this way the low efficiency of Refiners can be understood, ultimately to clarify the design rules for a more effective refiner. The modelling focuses on the role of particle size distribution. This is in conjunction with measurements (by scanning electron microscopy and image analysis) of the particle size distributions in commercial Al-5Ti-1B Refiners known to have differing performances. The undercooling required for heterogeneous nucleation of oc-Al on the surface of potent TiB2 particles is extremely low. Accordingly, the modelling is based on the assumption that the critical step for a particle to behave as an active growth centre is that required to initiate free growth from the particle surface, rather than the initial heterogeneous nucleation event. It is considered that further initiation of free growth of crystals is stopped by the onset of recalescence in the melt during solidification. Only those particles which are active growth centres at the point of recalescence will contribute towards the final grain size. Negligible interference between particles and spherical growth up to the point of recalescence are assumed; these assumptions are rigorously tested. The model tests the effect of varying the particle size distribution by using measured distributions from ‘good’ and ‘poor’ Refiners. The variation of grain size with addition rate of refiner is examined. The model predicts an effective saturation, beyond which further addition has little effect. In general, good agreement is found between the grain-size predictions and conventional grain-refining tests.
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The effect of the size distribution of inoculant particles on as-cast grain size in aluminium alloys
Acta Materialia, 2004Co-Authors: T.e. Quested, A.l. GreerAbstract:A model based on free-growth control of grain initiation can quantitatively predict the grain size in aluminium alloys inoculated with commercial refiner as a function of refiner addition level, solute content in the melt and cooling rate. This model is applied to predict the performance of Refiners with hypothetical size distributions of nucleant particles. The distributions are log-normal, like those in commercial Refiners, but the mean particle diameter and the relative spread of the distribution are varied to map the performance of the refiner in giving minimum grain size, maximum efficiency, or minimum sensitivity of grain size to cooling rate. The optimal nucleant particle size distribution is a compromise between these aims and depends on the alloy and processing conditions. This mapping can assist in choosing between available Refiners or in developing improved Refiners. Existing commercial Refiners are highly effective, but their nucleant particle size distribution leaves room for improvement.
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modelling of inoculation of metallic melts application to grain refinement of aluminium by al ti b
Acta Materialia, 2000Co-Authors: A.l. Greer, A M Bunn, A Tronche, P V Evans, D J BristowAbstract:A numerical model is presented for the prediction of grain size in inoculated castings and is tested against measured grain sizes obtained in standard grain-refiner tests on aluminium alloys. It is shown that for potent nucleants, such as commercial grain Refiners for aluminium, the nucleation stage itself is not the controlling factor. The number of grains is determined by a free-growth condition in which a grain grows from a refiner particle at an undercooling inversely proportional to the particle diameter. With measured particle size distributions as input, the model makes quantitatively correct predictions for grain size and its variation with refiner addition level, cooling rate and melt composition. The model can assist in optimizing the use of existing Refiners and in developing improved Refiners.
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grain refinement by al ti b alloys in aluminium melts a study of the mechanisms of poisoning by zirconium
Materials Science and Technology, 1999Co-Authors: A M Bunn, M A Kearns, Peter Schumacher, C B Boothroyd, A.l. GreerAbstract:AbstractConventional grain refining tests confirm that the presence of zirconium in commercial purity aluminium melts dramatically reduces the effectiveness of Al–Ti–B grain Refiners. Quantitative comparisons suggest that this poisoning action cannot be attributed solely to reduction in growth restriction arising from changed solute contents in the melt. Microscopic analysis of TiB2 particles in an aluminium based, zirconium containing metallic glass shows the potential for substitution of zirconium for titanium. Analysis of a conventional Al–5 wt-%Ti–1 wt-%B refiner doped with zirconium shows the potential for similar modification of Al3 Ti. Thus zirconium can affect the nucleation stage of grain refinement by substituting for titanium in the aluminide and/or the boride phase, consistent with earlier work suggesting that the key to the nucleation potency is the existence of a layer of Al3 Ti on TiB2 particles.
S. A. Kori - One of the best experts on this subject based on the ideXlab platform.
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Effect of a grain refiner cum modifier on mechanical properties of Al-7Si and Al-11Si alloys
Metals and Materials International, 2013Co-Authors: S. M. Jigajinni, K. Venkateswarlu, S. A. KoriAbstract:This study evaluates the influence of grain Refiners/modifiers on the mechanical properties of the Al-7Si and Al-11Si alloys with an experiment of quantitative and qualitative correlations with the microstructure. Modification of Al-Si alloys with strontium additions and grain refinement with Al-Ti, Al-B and Al-T-B master alloy additions are demonstrated to be efficient on Al-Si alloys. A single master alloy with combined additions of Sr and Ti and/or B was prepared and the microstructure and mechanical properties were studied. The results show that boron rich (Al-3B-Sr and Al-1Ti-3B-Sr) master alloys are more efficient than Ti rich (Al-3Ti-Sr and Al-5Ti-1B-Sr) master alloys considering their combined grain refinement and modification effect on Al-7Si and Al-11Si alloys. However, the presence of Sr does not influence the grain refinement. Similarly, presence of grain refiner does not influence the modification of eutectic Si.
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Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying
International Materials Reviews, 2002Co-Authors: B.s. Murty, S. A. Kori, M. ChakrabortyAbstract:Grain refinement of aluminium and its alloys is common industrial practice. The field has been extensively investigated by many workers over the past 50 years, not only to develop efficient grain Refiners for different aluminium alloys, but also to achieve an understanding of the mechanism of grain refinement. The present review confines itself to the literature on grain refinement by heterogeneous nucleation and alloying. Initially, the fundamentals of grain refinement by inoculants are outlined. The types of grain refiner, Al-Ti-B master alloys in particular, and their methods of manufacture are next discussed. The grain refining tests to assess the efficiency of the grain Refiners and the grain refining behaviour of aluminium alloys are also discussed in brief. The performance of a grain refiner, as well as the response of an aluminium alloy to grain refinement, is influenced by the microstructure of the grain refiner as controlled by the process parameters involved in its preparation and the alloying elements present in the aluminium alloy. The roles of these factors, and particularly the roles of poisoning elements such as Si, Cr, Zr, Li, are reviewed. The paper also reviews the mechanisms of grain refinement, the fading and poisoning phenomena, and the trends in the development of new grain Refiners for aluminium alloys containing poisoning elements.
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development of an efficient grain refiner for al 7si alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: S. A. Kori, B.s. Murty, M. ChakrabortyAbstract:Abstract The response of Al–7Si alloy towards grain refinement by Al–Ti–B master alloys (with different Ti–B ratios) at different addition levels has been studied in detail. The results indicate that high B-containing master alloys are powerful grain Refiners when compared to conventional grain Refiners like Al–5Ti–lB master alloys. In the present study, indigenously developed master alloys have been used for the grain refinement of alloys Al–7Si and LM-25 . Significant improvements in mechanical properties have been obtained with a combination of grain refiner and Sr as modifier.
