Abstract Low strain cold deformation and annealing techniques have been applied to establish the ... more Abstract Low strain cold deformation and annealing techniques have been applied to establish the effects of composition and heat treatment variables on the recrystallisation behaviour of Al–Fe alloys. The parameters controlling the critical strain required to initiate recrystallisation and the grain size produced by subsequent recrystallisation annealing have been established to be the volume fraction of secondary phases, the eutectic colony size in both as cast and processed material, matrix composition, the initial grain size preceding final cold deformation, the amount of deformation before annealing, and the final annealing temperature. The results derived from the application of the strain annealing test showed that increasing the volume fraction of secondary precipitate phases, the homogenisation and final annealing temperatures, or the eutectic colony size, decreases the critical strain and increases the maximum grain size produced after annealing, but increasing the initial grain size has opposite...
Prealloyed materials of Al-7175 alloy were melted under controlled (vacuum) and normal atmosphere... more Prealloyed materials of Al-7175 alloy were melted under controlled (vacuum) and normal atmospheres and cast into a permanent cast iron mould (PMC) at various temperatures. Al-7175 alloy ribbons were produced by melt spinning (RSP). Specimens of both groups of materials were then solution treated in the temperature range of 400°C to 535°C for various times. RSP ribbons were also subjected to in-situ annealing operation (hot stage) in the TEM. The microstructural analyses were conducted on PMC ingots, RSP materials and soaked samples to establish and evaluate the influence of superheating temperature, rapid solidification and annealing conditions on the constituent phases and substructure. It was found that casting at 645°C and 670°C resulted in the formation of Al 23 CuFe 4 , Al 7 Cu 2 Fe, Mg 2 Si and a eutectic phase of AlMg-CuZn. In the case of the ingot poured at 950°C, similar phases occurred except Mg 2 Si The microstructure of RSP ribbons is composed of supersaturated α-Al soli...
International Journal of Cast Metals Research, 2017
An attempt has been made to develop an investment powder which expands significantly in the setti... more An attempt has been made to develop an investment powder which expands significantly in the setting period to meet the solidification shrinkage of most metals and alloys. Investment powders consisting of tricalcium aluminate, quartz, various sulphate bearing compounds and a small amounts of controlling agents (additives) were used in the preparation of the block investment molds. A413 Al-Si (Etial 140) alloy was melted and poured in these molds to cast a test specimen of a special geometry. The preliminary results show that it is possible to produce dimensionally accurate castings by using expansive type investment powders. Samples cast into block investment molds prepared from ordinary non-expansive investment powder were smaller than the pattern size, while those poured into molds produced from expansive type powders were the same size or greater than the pattern size.
The recrystallisation of a super-pure Al-0.5% Fe alloy has been investigated using differential s... more The recrystallisation of a super-pure Al-0.5% Fe alloy has been investigated using differential scanning calorimetry. Due to the absence of large thermal effects resulting either from precipitation or from dissolution processes, it was possible to measure the stored energy of cold-deformed specimens, released during recrystallisation, by annealing in the calorimeter. Results derived from specimens of permanent-mould and direct-chill cast materials indicate that the stored energy of cold work and the recrystallisation temperature are determined to a large extent by the casting practice-induced microstructural features of the cast slabs which permeate throughout the subsequent processing
Cellular metals differ from the other materials by a lower density which is their characteristic ... more Cellular metals differ from the other materials by a lower density which is their characteristic property. Besides, they show unusual physical, mechanical, thermal, acoustic and electrical properties. Even though they have lots of pores compared to solid materials they can show a unique combination of several properties that cannot be obtained in a conventional material at the same time. There are several kinds of production methods for cellular materials. Nowadays, lots of researches have been carried out with respect to new production methods. The lost foam process, which bases on evaporating the polystyrene foam model, reduces the process steps of investment casting and can be an alternative method to many production methods. In this study, open cell samples were produced with two different aluminium alloys by using the lost foam casting technique. A413 as a casting alloy and A6063 as a wrought alloy were selected for casting experiments. After production of these two aluminium a...
In this study surface finish and dimensional charactersitics of castings produced with gypsum bon... more In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze was subsequently cast into these moulds by vacuum assisted casting process. Afterwards, surface roughnesses of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percantage of dimensional change.
In this study surface finish and dimensional charactersitics of castings produced with gypsum bon... more In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze and sterling silver were subsequently cast into these moulds by vacuum assisted and vacuum pressure casting processes, respectively. Afterwards, surface roughness of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percentage of dimensional change.
Materials Fabrication, Properties, Characterization, and Modeling, 2011
... Fatih Toptan, Isil Kerti, Ahmet Sagin, Mustafa Cigdem, Sibel Daglilar, Fatih Yuksel ... Kerti... more ... Fatih Toptan, Isil Kerti, Ahmet Sagin, Mustafa Cigdem, Sibel Daglilar, Fatih Yuksel ... Kerti and F. Toptan, Mater Lett 62 (2008) 1215-1218 4.R. Ipek,, J Mater Process Tech 162-163 (2005) 71-75 5.F. Bedir, Mater Des 28 (2007) 1238-1244 6. A. Kalkanh and S. Yilmaz, Mater Des 29 ...
In aluminium-melting operations, a dross layer containing 85% metallic Al forms on the surface of... more In aluminium-melting operations, a dross layer containing 85% metallic Al forms on the surface of the molten aluminium bath. Therefore, a significant amount of metal is removed from the furnace with the dross. Melt lossesare one of the most important economical points in the melting operations. In the first part of the present study, a series of reverbaratory furnace drosses received from several aluminium plants located in Turkey were examined to determine their compositional and structural characteristics. Following crushing and grinding operations, drosses were dimensionally classified into 5 groups. Metallic Al, Mg, Zn, Fe and SiO 2 contents of each group were analyzed separately. The metallic aluminium content of the group +4 mm is found to be approximately 75% while that of -0.5 mm group is 25%. Another fundamental finding is the high Mg content present in the drosses. Furthermore, Fe and SiO 2 contents increase with decreasing particle size of the dross. In the second part of the investigation, experiments were carried out on the treatment of the salty slags to obtain salt, aluminium and non-metallic products which can be used for various purposes. Leaching and crystallization in an evaporator is employed to determine the optimum conditions for the recovery of flux from the salty slag.
Abstract The dependence of critical strain and subsequent selective abnormal growth of large grai... more Abstract The dependence of critical strain and subsequent selective abnormal growth of large grains in commercial purity aluminium containing 0.5 wt.% Fe on ingot structures has been studied. Wedge-shaped strain-annealed specimens taken from sand-cast and direct-chill-cast slabs were cold rolled which gave a strain gradient ranging from 0 to 25%, and after annealing at selected temperatures for 1 h the structures were assessed. The current work also investigated the effects that heat treatment (homogenization) and other processing variables might have on critical strain and maximum grain size values. It has been shown that a satisfactory final structure can result from widely differing cast structures (casting operations) by appropriate combinations of the operational variables; provided that the characteristics of deformation and annealing are controlled it is possible to avoid the occurrence of abnormal or critical grain growth in the processed products.
International Journal of Cast Metals Research, 2010
... 4. V. Faccenda and GM Ingo: J. Gold Technol., 2001, 31, 1–4. 5. E. Lodovici, J. Barbosa, C. M... more ... 4. V. Faccenda and GM Ingo: J. Gold Technol., 2001, 31, 1–4. 5. E. Lodovici, J. Barbosa, C. Meira and L. Eloy: Dent. ... 11. AO Devecili and B. Yılmaz, 'Production and properties of dental plasters', Graduation project, Yıldız Technical University, Istanbul, Turkey, 2005. 12. ...
The precipitation characteristics of the secondary phases and the microstructural features of the... more The precipitation characteristics of the secondary phases and the microstructural features of the melt-spun (RSP) and annealed Al-7175 alloy ribbons have been studied using optical and analytical electron microscopy. Also investigated were the changes in size and type of secondary precipitate phases and grains during in-situ annealing operation (hot stage) in the TEM to highlight the formation and dissolution characteristics of the intermetallics. The results derived from the analyses of the untreated specimens have shown that rapidly solidified RSP ribbons are composed of supersaturated α-Al solid solution. Subsequent annealing heat treatment conducted over the temperature range 400 o C to 500 o C leads to the precipitation of a number of phases some of which disappear on further annealing at a temperature of 535 o C. In the case of hot stage annealing, precipitation occurred in both thinner and thicker regions of the RSP ribbons up to temperatures of 400 o C. Further heating led t...
Abstract Low strain cold deformation and annealing techniques have been applied to establish the ... more Abstract Low strain cold deformation and annealing techniques have been applied to establish the effects of composition and heat treatment variables on the recrystallisation behaviour of Al–Fe alloys. The parameters controlling the critical strain required to initiate recrystallisation and the grain size produced by subsequent recrystallisation annealing have been established to be the volume fraction of secondary phases, the eutectic colony size in both as cast and processed material, matrix composition, the initial grain size preceding final cold deformation, the amount of deformation before annealing, and the final annealing temperature. The results derived from the application of the strain annealing test showed that increasing the volume fraction of secondary precipitate phases, the homogenisation and final annealing temperatures, or the eutectic colony size, decreases the critical strain and increases the maximum grain size produced after annealing, but increasing the initial grain size has opposite...
Prealloyed materials of Al-7175 alloy were melted under controlled (vacuum) and normal atmosphere... more Prealloyed materials of Al-7175 alloy were melted under controlled (vacuum) and normal atmospheres and cast into a permanent cast iron mould (PMC) at various temperatures. Al-7175 alloy ribbons were produced by melt spinning (RSP). Specimens of both groups of materials were then solution treated in the temperature range of 400°C to 535°C for various times. RSP ribbons were also subjected to in-situ annealing operation (hot stage) in the TEM. The microstructural analyses were conducted on PMC ingots, RSP materials and soaked samples to establish and evaluate the influence of superheating temperature, rapid solidification and annealing conditions on the constituent phases and substructure. It was found that casting at 645°C and 670°C resulted in the formation of Al 23 CuFe 4 , Al 7 Cu 2 Fe, Mg 2 Si and a eutectic phase of AlMg-CuZn. In the case of the ingot poured at 950°C, similar phases occurred except Mg 2 Si The microstructure of RSP ribbons is composed of supersaturated α-Al soli...
International Journal of Cast Metals Research, 2017
An attempt has been made to develop an investment powder which expands significantly in the setti... more An attempt has been made to develop an investment powder which expands significantly in the setting period to meet the solidification shrinkage of most metals and alloys. Investment powders consisting of tricalcium aluminate, quartz, various sulphate bearing compounds and a small amounts of controlling agents (additives) were used in the preparation of the block investment molds. A413 Al-Si (Etial 140) alloy was melted and poured in these molds to cast a test specimen of a special geometry. The preliminary results show that it is possible to produce dimensionally accurate castings by using expansive type investment powders. Samples cast into block investment molds prepared from ordinary non-expansive investment powder were smaller than the pattern size, while those poured into molds produced from expansive type powders were the same size or greater than the pattern size.
The recrystallisation of a super-pure Al-0.5% Fe alloy has been investigated using differential s... more The recrystallisation of a super-pure Al-0.5% Fe alloy has been investigated using differential scanning calorimetry. Due to the absence of large thermal effects resulting either from precipitation or from dissolution processes, it was possible to measure the stored energy of cold-deformed specimens, released during recrystallisation, by annealing in the calorimeter. Results derived from specimens of permanent-mould and direct-chill cast materials indicate that the stored energy of cold work and the recrystallisation temperature are determined to a large extent by the casting practice-induced microstructural features of the cast slabs which permeate throughout the subsequent processing
Cellular metals differ from the other materials by a lower density which is their characteristic ... more Cellular metals differ from the other materials by a lower density which is their characteristic property. Besides, they show unusual physical, mechanical, thermal, acoustic and electrical properties. Even though they have lots of pores compared to solid materials they can show a unique combination of several properties that cannot be obtained in a conventional material at the same time. There are several kinds of production methods for cellular materials. Nowadays, lots of researches have been carried out with respect to new production methods. The lost foam process, which bases on evaporating the polystyrene foam model, reduces the process steps of investment casting and can be an alternative method to many production methods. In this study, open cell samples were produced with two different aluminium alloys by using the lost foam casting technique. A413 as a casting alloy and A6063 as a wrought alloy were selected for casting experiments. After production of these two aluminium a...
In this study surface finish and dimensional charactersitics of castings produced with gypsum bon... more In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze was subsequently cast into these moulds by vacuum assisted casting process. Afterwards, surface roughnesses of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percantage of dimensional change.
In this study surface finish and dimensional charactersitics of castings produced with gypsum bon... more In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze and sterling silver were subsequently cast into these moulds by vacuum assisted and vacuum pressure casting processes, respectively. Afterwards, surface roughness of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percentage of dimensional change.
Materials Fabrication, Properties, Characterization, and Modeling, 2011
... Fatih Toptan, Isil Kerti, Ahmet Sagin, Mustafa Cigdem, Sibel Daglilar, Fatih Yuksel ... Kerti... more ... Fatih Toptan, Isil Kerti, Ahmet Sagin, Mustafa Cigdem, Sibel Daglilar, Fatih Yuksel ... Kerti and F. Toptan, Mater Lett 62 (2008) 1215-1218 4.R. Ipek,, J Mater Process Tech 162-163 (2005) 71-75 5.F. Bedir, Mater Des 28 (2007) 1238-1244 6. A. Kalkanh and S. Yilmaz, Mater Des 29 ...
In aluminium-melting operations, a dross layer containing 85% metallic Al forms on the surface of... more In aluminium-melting operations, a dross layer containing 85% metallic Al forms on the surface of the molten aluminium bath. Therefore, a significant amount of metal is removed from the furnace with the dross. Melt lossesare one of the most important economical points in the melting operations. In the first part of the present study, a series of reverbaratory furnace drosses received from several aluminium plants located in Turkey were examined to determine their compositional and structural characteristics. Following crushing and grinding operations, drosses were dimensionally classified into 5 groups. Metallic Al, Mg, Zn, Fe and SiO 2 contents of each group were analyzed separately. The metallic aluminium content of the group +4 mm is found to be approximately 75% while that of -0.5 mm group is 25%. Another fundamental finding is the high Mg content present in the drosses. Furthermore, Fe and SiO 2 contents increase with decreasing particle size of the dross. In the second part of the investigation, experiments were carried out on the treatment of the salty slags to obtain salt, aluminium and non-metallic products which can be used for various purposes. Leaching and crystallization in an evaporator is employed to determine the optimum conditions for the recovery of flux from the salty slag.
Abstract The dependence of critical strain and subsequent selective abnormal growth of large grai... more Abstract The dependence of critical strain and subsequent selective abnormal growth of large grains in commercial purity aluminium containing 0.5 wt.% Fe on ingot structures has been studied. Wedge-shaped strain-annealed specimens taken from sand-cast and direct-chill-cast slabs were cold rolled which gave a strain gradient ranging from 0 to 25%, and after annealing at selected temperatures for 1 h the structures were assessed. The current work also investigated the effects that heat treatment (homogenization) and other processing variables might have on critical strain and maximum grain size values. It has been shown that a satisfactory final structure can result from widely differing cast structures (casting operations) by appropriate combinations of the operational variables; provided that the characteristics of deformation and annealing are controlled it is possible to avoid the occurrence of abnormal or critical grain growth in the processed products.
International Journal of Cast Metals Research, 2010
... 4. V. Faccenda and GM Ingo: J. Gold Technol., 2001, 31, 1–4. 5. E. Lodovici, J. Barbosa, C. M... more ... 4. V. Faccenda and GM Ingo: J. Gold Technol., 2001, 31, 1–4. 5. E. Lodovici, J. Barbosa, C. Meira and L. Eloy: Dent. ... 11. AO Devecili and B. Yılmaz, 'Production and properties of dental plasters', Graduation project, Yıldız Technical University, Istanbul, Turkey, 2005. 12. ...
The precipitation characteristics of the secondary phases and the microstructural features of the... more The precipitation characteristics of the secondary phases and the microstructural features of the melt-spun (RSP) and annealed Al-7175 alloy ribbons have been studied using optical and analytical electron microscopy. Also investigated were the changes in size and type of secondary precipitate phases and grains during in-situ annealing operation (hot stage) in the TEM to highlight the formation and dissolution characteristics of the intermetallics. The results derived from the analyses of the untreated specimens have shown that rapidly solidified RSP ribbons are composed of supersaturated α-Al solid solution. Subsequent annealing heat treatment conducted over the temperature range 400 o C to 500 o C leads to the precipitation of a number of phases some of which disappear on further annealing at a temperature of 535 o C. In the case of hot stage annealing, precipitation occurred in both thinner and thicker regions of the RSP ribbons up to temperatures of 400 o C. Further heating led t...
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