Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 5
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

Recyclability is one of the great features of aluminium and its alloys. However, it has been typically considered that the secondary aluminium quality is low and bad. This is only because aluminium is so sensitive to turbulence. Uncontrolled transfer and handling of the liquid aluminium results in formation of double oxide defects known as bifilms. Bifilms are detrimental defects. They form porosity and deteriorate the properties. The detection and quantification of bifilms in liquid aluminium can be carried out by bifilm index measured in millimetres as an indication of melt cleanliness using Reduced Pressure Test (RPT). In this work, recycling efficiency and quality change of A356 alloy with various Ti additions have been investigated. The charge was recycled three times and change in bifilm index and bifilm number was evaluated. It was found that when high amount of Ti grain refiner was added, the melt quality was increased due to sedimentation of bifilms with Ti. When low amount of Ti is added, the melt quality was degraded.

Go to article

Authors and Affiliations

O. Gursoy
E. Erzi
K. Tur
D. Dispinar
ORCID: ORCID
Download PDF Download RIS Download Bibtex

Abstract

Porosity is one of the major problems in casting operations and there are several discussions in the literature about the porosity formation in aluminum castings. Bifilms are the defects that are introduced into the melt by turbulence. They can be detected with reduced pressure test and presented numerically by measuring bifilm index. The measure of bifilm index is the sum of total oxide length given in millimeters from the cross-section of reduced pressure test sample solidified under 0.01 MPa. In this work, low pressure die casting (LPDC) unit was built in an attempt to enhance the producibility rate. The unit consists of a pump housing that was placed inside the melt in the melting furnace where the pressure was applied instead of the whole melt surface. It was observed that the melt quality of A356 alloy was deteriorated over time which had led to higher porosity. This was attributed to the increased oxide thickness of the bifilm by the consumption of air in between the folded oxides. A relationship was found between bifilm index and pore formation.
Go to article

Bibliography

[1] Campbell, J. (2011). Complete Casting Handbook: Metal Casting Processes. Techniques and Design. Elsevier Science.
[2] Bonollo, F., Urban, J., Bonatto, B. & Botter, M. (2005). Gravity and low pressure die casting of aluminium alloys: a technical and economical benchmark. La Metallurgia Italiana. 6, 23-32.
[3] Dispinar, D. & J. Campbell, (2004). Critical assessment of reduced pressure test. Part 2: Quantification. International Journal of Cast Metals Research. 17(5), 287-294.
[4] Raiszadeh, R., & Griffiths, W.D. (2006). A method to study the history of a double oxide film defect in liquid aluminum alloys. Metallurgical and Materials Transactions B. 37(6), 865-871.
[5] Raiszadeh, R., & Griffiths, W.D. (2008). A semi-empirical mathematical model to estimate the duration of the atmosphere within a double oxide film defect in pure aluminum alloy. Metallurgical and Materials Transactions B. 39(2), 298-303.
[6] Raiszadeh, R., & Griffiths, W.D. (2011). The effect of holding liquid aluminum alloys on oxide film content. Metallurgical and Materials Transactions B. 42(1), 133-143.
[7] Aryafar, M., Raiszadeh, R., & Shalbafzadeh, A. (2010). Healing of double oxide film defects in A356 aluminium melt. Journal of materials science. 45(11), 3041-3051.
[8] Farhoodi, B., Raiszadeh, R., & Ghanaatian, M. H. (2014). Role of double oxide film defects in the formation of gas porosity in commercial purity and Sr-containing Al alloys. Journal of Materials Science & Technology. 30(2), 154-162.
[9] Amirinejhad, S., Raiszadeh, R., & Doostmohammadi, H. (2013). Study of double oxide film defect behaviour in liquid Al–Mg alloys. International Journal of Cast Metals Research. 26(6), 330-338.
[10] Bakhtiarani, F.N., & Raiszadeh, R. (2011). Healing of double-oxide film defects in commercial purity aluminum melt. Metallurgical and Materials Transactions B. 42(2), 331-340.
[11] Bagherpour-Torghabeh, H., Raiszadeh, R., & Doostmohammadi, H. (2017). Role of Mechanical Stirring of Al-Mg Melt in the Healing of Bifilm Defect. Metallurgical and Materials Transactions B. 48(6), 3174-3184.
[12] Nateghian, M., Raiszadeh, R., & Doostmohammadi, H. (2012). Behavior of Double-Oxide Film Defects in Al-0.05 wt pct Sr Alloy. Metallurgical and Materials Transactions B. 43(6), 1540-1549.
[13] Stefanescu, D.M. (2005). Computer simulation of shrinkage related defects in metal castings - a review. International Journal of Cast Metals Research. 18, 129-143.
[14] Zhu, J.D., Cockcroft, S.L., Maijer, D.M. & Ding, R. (2005). Simulation of microporosity in A356 aluminium alloy castings. International Journal of Cast Metals Research. 18, 229-235.
[15] Merlin, M., Timelli, G., Bonollo, F. & Garagnani, G.L. (2009). Impact behaviour of A356 alloy for low-pressure die casting automotive wheels. Journal of Materials Processing Technology. 209(2), 1060-1073.
[16] Zhang, B., Maijer, D.M. & Cockcroft, S.L. (2007). Development of a 3-D thermal model of the low-pressure die-cast (LPDC) process of A356 aluminum alloy wheels. Materials Science and Engineering: A, 464(1-2), 295-305.
[17] Zhang, B., Cockcroft, S.L., Maijer, D.M., Zhu, J.D. & Phillion, A.B. Casting defects in low-pressure die-cast aluminum alloy wheels. JOM Journal of the Minerals, Metals and Materials Society, 57(11), 36-43.
[18] Campbell, J. (1968). Hydrostatic tensions in solidifying materials. Transactions of the Metallurgical Society of AIME, 242 (February), 264-267.
[19] Campbell, J. (1968). Hydrostatic tensions in solidifying alloys. Transactions of the Metallurgical Society of AIME, 242 (February), 268-271.
[20] Campbell, J. (1967), Shrinkage pressure in castings (The solidification of a Metal Sphere). Transactions of the Metallurgical Society of AIME, 239 (February), 138-142.
[21] Dispinar, D. & Campbell, J. (2004). Critical assessment of reduced pressure test. Part 1: Porosity phenomena. International Journal of Cast Metals Research. 17(5), 280-286.
[22] Dispinar, D., Akhtar, S., Nordmark, A., Di Sabatino, M., & Arnberg, L. (2010). Degassing, hydrogen and porosity phenomena in A356. Materials Science and Engineering: A. 527(16-17), 3719-3725.
[23] Puga, H., Barbosa, J., Azevedo, T., Ribeiro, S. & Alves, J.L. (2016). Low pressure sand casting of ultrasonically degassed AlSi7Mg0. 3 alloy: Modelling and experimental validation of mould filling. Materials & Design. 94, 384-391.
[24] El-Sayed, M.A. & Essa, K. (2018). Effect of mould type and solidification time on bifilm defects and mechanical properties of Al–7si–0.3 mg alloy castings. Computational and Experimental Studies, 23.
[25] Gyarmati, G., Fegyverneki, G., Mende, T. & Tokár, M. (2019). Characterization of the double oxide film content of liquid aluminum alloys by computed tomography. Materials Characterization. 157, 109925. [26] Gyarmati, G., Fegyverneki, G., Tokár, M., & Mende, T. (2020). The Effects of Rotary Degassing Treatments on the Melt Quality of an Al–Si Casting Alloy. International Journal of Metalcasting. 1-11.
[27] Tiryakioğlu, M. (2020). The Effect of Hydrogen on Pore Formation in Aluminum Alloy Castings: Myth Versus Reality. Metals. 10(3), 368.
[28] Tiryakioğlu, M. (2019). Solubility of hydrogen in liquid aluminium: reanalysis of available data. International Journal of Cast Metals Research. 32(5-6), 315-318.
[29] Tiryakioğlu, M. (2020). A simple model to estimate hydrogen solubility in liquid aluminium alloys. International Journal of Cast Metals Research. 1-3.
Go to article

Authors and Affiliations

O. Gursoy
1
A. Nordmak
2
F. Syvertsen
2
M. Colak
3
K. Tur
4
D. Dispinar
5
ORCID: ORCID

  1. University of Padova, Italy
  2. SINTEF, Norway
  3. University of Bayburt, Turkey
  4. Atilim University, Turkey
  5. Istanbul Technical University, Turkey
Download PDF Download RIS Download Bibtex

Abstract

Production of the defect-free casting of aluminium alloys is the biggest challenge. Porosity is known to be the most important defect. Therefore, many cast parts are subjected to several non-destructive tests in order to check their acceptability. There are several standards, yet, the acceptance limit of porosity size and distribution may change according to the customer design and requirements. In this work, the aim was targeted to evaluate the effect of size, location, and distribution of pores on the tensile properties of cast A356 alloy. ANSYS software was used to perform stress analysis where the pore sizes were changed between 0.05 mm to 3 mm by 0.05 mm increments. Additionally, pore number was changed from 1 to 5 where they were placed at different locations in the test bar. Finally, bifilms were placed inside the pore at different sizes and orientations. The stress generated along the pores was recorded and compared with the fracture stress of the A356 alloy. It was found that as the bifilm size was getting smaller, their effect on tensile properties was lowered. On the other hand, as bifilms were larger, their orientation became the dominant factor in determining the fracture.
Go to article

Bibliography

[1] Buffiere, J.-Y., Savelli, S., Jouneau, P.-H., Maire, E. & Fougeres, R. (2001). Experimental study of porosity and its relation to fatigue mechanisms of model Al–Si7–Mg0. 3 cast Al alloys. Materials Science and Engineering: A. 316(1-2), 115-126. DOI: 10.1016/S0921-5093(01)01225-4.
[2] Dispinar, D. & Campbell, J. (2011). Porosity, hydrogen and bifilm content in Al alloy castings. Materials Science and Engineering: A. 528(10-11), 3860-3865. DOI: 10.1016/j.msea.2011.01.084.
[3] Dispinar, D. & Campbell, J. (2004). Critical assessment of reduced pressure test. Part 1: Porosity phenomena. International Journal of Cast Metals Research. 17, 280-286. DOI: 10.1179/136404604225020696.
[4] Dispinar, D. & Campbell, J. (2004). Critical assessment of reduced pressure test. Part 2: Quantification. International Journal of Cast Metals Research. 17, 287-294. DOI: 10.1179/136404604225020704.
[5] Dispinar, D. & Campbell, J. (2006). Use of bifilm index as an assessment of liquid metal quality. International Journal of Cast Metals Research. 19, 5-17. DOI: 10.1179/136404606225023300.
[6] Dispinar, D. & Campbell, J. (2007). Effect of casting conditions on aluminium metal quality. Journal of Materials Processing Technology. 182, 405-410. DOI: 10.1016/j.jmatprotec.2006.08.021.
[7] Campbell, J. (2015). Complete casting handbook: metal casting processes, metallurgy, techniques and design. Butterworth-Heinemann.
[8] Dispinar, D. & Campbell, J. (2014). Reduced pressure test (RPT) for bifilm assessment. in Shape Casting: 5th International Symposium 2014, 243-251.
[9] Asadian Nozari, M., Taghiabadi, R., Karimzadeh, M. & Ghoncheh, M. H. (2015). Investigation on beneficial effects of beryllium on entrained oxide films, mechanical properties and casting reliability of Fe-rich Al–Si cast alloy. Materials Science and Technology. 31, 506-512. DOI: 10.1179/1743284714Y.0000000656.
[10] Bagherpour-Torghabeh, H., Raiszadeh, R. & Doostmohammadi, H. (2017). Role of Mechanical Stirring of Al-Mg Melt in the Healing of Bifilm Defect. Metallurigical and Materials Transactions B. 48, 3174-3184. DOI: 10.1007/s11663-017-1067-9.
[11] Bjurenstedt, A., Seifeddine, S. & Jarfors, A. E. W. (2015). On the complexity of the relationship between microstructure and tensile properties in cast aluminum. International Journal of Modern Physics B. 29, 1540011. DOI: 10.1142/S0217979215400111.
[12] Bozchaloei, G. E., Varahram, N., Davami, P. & Kim, S. K. (2012). Effect of oxide bifilms on the mechanical properties of cast Al–7Si–0.3 Mg alloy and the roll of runner height after filter on their formation. Materials Science and Engineering A. 548, 99-105. DOI: 10.1016/j.msea.2012.03.097.
[13] Çolak, M., Kayikci, R. & Dispinar, D. (2016). Melt cleanliness comparison of chlorine fluxing and ar degassing of secondary Al-4Cu. Metallurgical and Materials Transactions B. 47, 2705-2709. DOI: 10.1007/s11663-016-0745-3.
[14] Davami, P., Kim, S. K. & Varahram, N. (2012). Effects of hydrogen and oxides on tensile properties of Al–Si–Mg cast alloys. Materials Science and Engineering A. 552, 36-47. DOI: 10.1016/j.msea.2012.04.111.
[15] Davami, P., Kim, S. K. & Tiryakioğlu, M. (2013). The effect of melt quality and filtering on the Weibull distributions of tensile properties in Al–7% Si–Mg alloy castings. Materials Science and Engineering A. 579, 64-70. DOI: 10.1016/j.msea.2013.05.014.
[16] Dispinar, D., Akhtar, S., Nordmark, A., Di Sabatino, M. & Arnberg, L. (2010). Degassing, hydrogen and porosity phenomena in A356. Materials Science and Engineering A. 527, 3719-3725. DOI: 10.1016/j.msea.2010.01.088.
[17] El-Sayed, M. A., Hassanin, H. & Essa, K. (2016). Bifilm defects and porosity in Al cast alloys. The International Journal of Advanced Manufacturing Technology. 86, 1173-1179. DOI: 10.1007/s00170-015-8240-6.
[18] El-Sayed, M. A., Hassanin, H. & Essa, K. (2016). Effect of casting practice on the reliability of Al cast alloys. International Journal of Cast Metals Research. 29, 350-354. DOI: 10.1080/13640461.2016.1145966.
[19] El-Sayed, M. A., Salem, H. A. G., Kandeil, A. Y. & Griffiths, W. D. (2014). Determination of the lifetime of a double-oxide film in al castings. Metallurgical and Materials Transactions B. 45, 1398-1406. DOI: 10.1007/s11663-014-0035-x.
[20] Erzi, E., Gürsoy, Ö., Yüksel, Ç., Colak, M. & Dispinar, D. (2019). Determination of acceptable quality limit for casting of A356 aluminium alloy: supplier’s quality index (SQI). Metals. 9, 957. DOI: 10.3390/met9090957.
[21] Fiorese, E., Bonollo, F., Timelli, G., Arnberg, L. & Gariboldi, E. (2015). New classification of defects and imperfections for aluminum alloy castings. International Journal of Metalcasting. 9, 55-66. DOI: 10.1007/BF03355602.
[22] Gopalan, R. & Prabhu, N. K. (2011). Oxide bifilms in aluminium alloy castings–a review. Materials Science and Technology. 27, 1757-1769. DOI: 10.1179/1743284711Y.0000000033.
[23] Hsu, F.-Y., Jolly, M. R. & Campbell, J. (2007). The design of L-shaped runners for gravity casting. in Metals & Materials Society The Minerals, Proceedings of Shape Casting: 2nd International Symposium, Orlando, FL, USA.
[24] Kang, M. et al. (2014). Tensile properties and microstructures of investment complex shaped casting. Materials Science and Technology. 30, 1349-1353. DOI: 10.1179/1743284713Y.0000000444.
[25] Mostafaei, M., Ghobadi, M., Eisaabadi, G., Uludağ, M. & Tiryakioğlu, M. (2016). Evaluation of the effects of rotary degassing process variables on the quality of A357 aluminum alloy castings. Metallurgical and Materials Transactions B. 47, 3469-3475. DOI: 10.1007/s11663-016-0786-7.
[26] Puga, H., Barbosa, J., Azevedo, T., Ribeiro, S. & Alves, J. L. (2016). Low pressure sand casting of ultrasonically degassed AlSi7Mg0.3 alloy: modelling and experimental validation of mould filling. Materials and Design. 94, 384-391. DOI: 10.1016/j.matdes.2016.01.059.
[27] Stefanescu, D. M. (2005). Computer simulation of shrinkage related defects in metal castings–a review. International Journal of Cast Metals Research. 18, 129-143. DOI: 10.1179/136404605225023018.
[28] Tiryakioğlu, M., Campbell, J. & Nyahumwa, C. (2011). Fracture surface facets and fatigue life potential of castings. Metallurgical and Materials Transactions B. 42, 1098-1103. DOI: 10.1007/s11663-011-9577-3.
[29] Tunçay, T. & Bayoğlu, S. (2017). The effect of iron content on microstructure and mechanical properties of A356 cast alloy. Metallurgical and Materials Transactions B. 48, 794-804. DOI: 10.1007/s11663-016-0909-1.
[30] Tunçay, T., Tekeli, S., Özyürek, D. & Dispinar, D. (2017). Microstructure–bifilm interaction and its relation with mechanical properties in A356. International Journal of Cast Metals Research. 30, 20-29. DOI: 10.1080/13640461.2016.1192826.
[31] Uludağ, M., Çetin, R., Dispinar, D. & Tiryakioğlu, M. (2017). Characterization of the Effect of Melt Treatments on Melt Quality in Al-7wt %Si-Mg Alloys. Metals. 7(5), 157. DOI: 10.3390/met7050157.
[32] Uludağ, M., Çetin, R., Dişpinar, D. & Tiryakioğlu, M. (2018). On the interpretation of melt quality assessment of A356 aluminum alloy by the reduced pressure test: the bifilm index and its physical meaning. International Journal of Metalcasting. 12, 853–860. DOI: 10.1007/s40962-018-0217-4.
[33] Yorulmaz, A., Erzi, E., Gursoy, O. & Dispinar, D. (2019). End product rejection rate and its correlation with melt treatment in direct-chill casted hot rolling slabs. International Journal of Cast Metals Research. 32, 164-170. DOI: 10.1080/13640461.2019.1598684.
[34] Zahedi, H. et al. (2007). The effect of Fe-rich intermetallics on the Weibull distribution of tensile properties in a cast Al-5 pct Si-3 pct Cu-1 pct Fe-0.3 pct Mg alloy. Metallurgical and Materials Transactions A. 38, 659-670. DOI: 10.1007/s11661-006-9068-3.
[35] Kuwazuru, O. et al. (2008). X-ray CT inspection for porosities and its effect on fatigue of die cast aluminium alloy. Journal of Solid Mechanics and Materials Engineering. 2(9), 1220-1231. DOI: 10.1299/jmmp.2.1220.
[36] Le, V.-D., Saintier, N., Morel, F., Bellett, D. & Osmond, P. (2018). Investigation of the effect of porosity on the high cycle fatigue behaviour of cast Al-Si alloy by X-ray micro-tomography. International Journal of Fatigue. 106, 24-37. DOI: 10.1016/j.ijfatigue.2017.09.012.
[37] Wang, L. et al. (2016). Influence of pores on crack initiation in monotonic tensile and cyclic loadings in lost foam casting A319 alloy by using 3D in-situ analysis. Materials Science and Engineering A. 673, 362-372. DOI: 10.1016/j.msea.2016.07.036.
[38] Vincent, M., Nadot-Martin, C., Nadot, Y. & Dragon, A. (2014). Fatigue from defect under multiaxial loading: efect Stress Gradient (DSG) approach using ellipsoidal Equivalent Inclusion Method. International Journal of Fatigue. 59, 176-187. DOI: 10.1016/j.ijfatigue.2013.08.027.
[39] Gyarmati, G., Fegyverneki, G., Mende, T. & Tokár, M. (2019). Characterization of the double oxide film content of liquid aluminum alloys by computed tomography. Materials Characterization. 157, 109925. DOI: 10.1016/j.matchar.2019.109925.
[40] Kobayashi, M., Dorce, Y., Toda, H. & Horikawa, H. (2010). Effect of local volume fraction of microporosity on tensile properties in Al–Si–Mg cast alloy. Materials Science and Technology. 26, 962-967. DOI: 10.1179/174328409X 441283.
[41] Nikishkov, G. P. (2004). Introduction to the finite element method. Univ. Aizu 1-70.
Go to article

Authors and Affiliations

H. Sahin
1
ORCID: ORCID
M. Atik
1
F. Tezer
1
S. Temel
1
O. Aydin
1
O. Kesen
1
O. Gursoy
2
D. Dispinar
3
ORCID: ORCID

  1. Istanbul Technical University, Turkey
  2. University of Padova, Italy
  3. Foseco, Netherlands
Download PDF Download RIS Download Bibtex

Abstract

Al-4.5Cu alloys are widely used in aerospace industries due to their low weight and high mechanical properties. This group of aluminium alloys is known as 2xx series and exhibits the highest mechanical properties however this alloy is known to suffer from feedability and high tendency for hot tearing. Al-Si alloys (3xx) have improved fluidity and better feedability particularly by several modifications such as Ti, B or Sr. Eutectic temperature is decreased and mechanical properties can be enhanced. Yet, the strength values of this alloy group cannot reach the values of 2xx series. Therefore, in this study, the effect of Ag addition on the fluidity of Al-4.5Cu alloy has been investigated. Standard size spiral mould was used. The casting temperature was selected to be 770oC. Five castings were made and Weibull statistical approach was used to evaluate the results. In addition, coating of the die with BN was also investigated. It was found that Ag addition and BN coating of the die revealed the most reproducible, reliable and high fluidity values.

Go to article

Authors and Affiliations

K. Yildirim
M. Helvaci
Ö. Gürsoy
E. Erzi
C. Kahruman
D. Dispinar
Download PDF Download RIS Download Bibtex

Abstract

Aluminium alloys are one of the preferred materials especially for land and air transportation because of their high strength and lowdensity properties. Although production using casting method is economical yet it has some disadvantages. Shrinkage which is occurred due to the density difference between the solid and liquid metal is prevented by feeders which need to be calculated. Liquid metal should be transferred to the mould without any turbulence. As a result, sprues are needed to be designed precisely. On the other hand, aluminium alloys can also be shaped by forging at semi-solid temperatures. There are some advantages compared to the traditional forging methods of improving die life due to the lower tonnage values. In this study, semi-solid produced 7075 aluminium alloy die filling capabilities were investigated. To achieve semisolid structure strain induced melt activated method (SIMA) was used. The desired structure was achieved at 635 °C and 30 minutes of duration of heat treatment. After determining the optimum parameters, metallographic analysis, density calculations, porosity distribution and tensile tests were carried out. It was found that the reproducibility of SIMA produced 7075 alloy was quite low. A proper tensile test result was achieved only 7 of the total 15 tests and the mean value was 386 MPa. The main reason for this scattered in mechanical properties could be the chemical composition of the alloy and the rapid solidification of the liquid eutectic phases. It is important to define the best fitting process parameters and controlling them precisely will be the most important factors for future studies.
Go to article

Authors and Affiliations

E. Erzi
O. Gursoy
Ç.O.K. Yüksel
S. Kirtay
D. Dispinar

This page uses 'cookies'. Learn more