PROTEC-12068;No.of Pages 12 ARTICLE IN PRESS 0 JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-XXX ity,and low cost.They also investigated the influence of small world.Many of these researchers have used material prop- additions of Ca and Sr on the tensile and creep properties. erties which are obtained from tensile test results in their Another room temperature formability testing was performed investigations.However,information on properties obtained on an Al-Mg6.8 type alloy sheet with a fully recrystallized at elevated temperatures under a biaxial state of stress is structure (average grain diameter ~18um)and after partial limited.Mostly,they are not available for finite element sim- annealing with a retained deformed structure by Romhanji ulation.This area needs to be studied extensively. et al.(1998).The yield strengths attained after full recrystal- In terms of numerical simulations,there are no well lization and after partial annealing,were 175 and 283MPa, defined material models includingtemperature and strain rate respectively.Such an increase in strength is followed by forma- effects for aluminum alloy.Further investigations on material bility degradation,maximized around the plain strain state to models are required.In future study,material models should either 42%,as obtained using the limiting dome height test be developed and the effect of process parameters should be (LDH),or 35%after using forming limit curves(FLC).A com- investigated for process optimization. parison with known high-strength formable alloys has shown that the tested alloy in the recrystallized condition has a bet- ter stretch formability (at the same or even higher yield stress Acknowledgements level),while in the unrecrystallized-partially annealed con- dition it has a lower formability,limiting its application to This work is supported by The Scientific and Technologi- moderate forming requirements for very high-strength parts. cal Research Council of Turkey (TUBITAK).Project Number: 106M058,Title:"Experimental and Theoretical Investigations of The Effects of Temperature and Deformation Speed on 3.3. The effects of lubrication Formability".TUBITAK support is profoundly acknowledged. One of the important parameter for the forming of aluminum sheets is lubrication.It is used during the forming process REFERENCES to get better surface quality and to decrease the friction of die surfaces.This contributes to increasing the die life- time by reducing wear.Meiler et al.(2003)investigated the Abedrabbo,N.,Pourboghrat,F.,Carsley,J.,2007.Forming of effects of dry film lubricants on aluminum sheet metal form- AA5182-O and AA5754-O at elevated temperatures using ing and compared the results with other type lubricants.They coupled thermo-mechanical finite element models.Int.J Plast.23,841-875. observed that dry film lubricants showed advantages over con- Ahmetoglu,M.A.,Kinzel,G.,Altan,T.,1997.Forming of aluminum ventional oil lubricants because of their high deep drawing alloys-application of computer simulation and blank holding performance,especially on complex shaped body panels.They force control.J.Mater.Process.Technol.71,147-151. also emphasized in their study the formability is increased as Altan,T.,2002.Warm forming of aluminum alloys-academic a consequence of reduced friction and it is possible to get more exercise or practical opportunity?Stamping J.14,58-59. homogeneous sheet thickness distributions.Wu et al.(2006) ASM Metal Handbook,1988.Volume 14 Forming and Forging.9th studied a super plastic 5083 Al alloy under biaxial deformation ed.ASM International,Metals Park,Ohio,pp.791-804. Barlat,F.,Lian,J.,1989.Plastic behavior and stretchability of sheet by deforming the sheet into a rectangular die cavity with and metals.Part I.A yield function for orthotropic sheets under without lubrication.Results indicate that reducing the inter- plane stress conditions.Int.J.Plast.5,51-66 facial friction by use of a lubricant altered the metal flow after Barlat,F.,Lege,D.J.,Brem,J.C.,1991.A six-component yield the deformed sheet had made contact with the die surface. function for anisotropic materials.Int.J.Plast.7,693-712 Besides,they observed that changes of the metal flow dur- Barlat,F.,Maeda,Y.,Chung,K.,Yanagawa,M.,Brem,J.C. ing forming not only developed a better thickness distribution Hayashida,Y.,Lege,D.J.,Matsui,K.,Murtha,S.J.,Hattori,S. of the formed part,but also improved cavitations distribution Becker,R.C.,Makosey,S.,1997.Yield function development for aluminum alloy sheets.J.Mech.Phys.Solids 45(11/12), (Kelly and Cotterell,2002). 1727-1763 Barlat,F.,Brem,J.C.,Yoon,J.W.,Chung,K.,Dick,R.E.,Lege,D.J. Pourboghrat,F.,Choi,S.H.,Chu,E.,2003.Plane stress yield Conclusion function for aluminum alloy sheets.Part 1.Theory.Int.J.Plast 19,1297-1319. In this paper,formability of Al-Mg alloys at warm temperature Barlat,E.,Aretz,H.,Yoon,J.W.,Karabin,M.E.,Brem,J.C.,Dick,R.E., is presented.In general,at temperatures above 225C the flow 2005.Linear transformation-based anisotropic yield stress becomes strain rate dependent. functions.Int.J.Plast.21(5),1009-1039. Beer,F.P.,Johnston,E.R.,1992.Mechanics of Materials,Second ed The warm forming process is beneficial in terms of forma- McGraw-Hill,Inc,International ed. bility.Researchers have been conducted their studies at lab Bolt,P.J.,Lamboo,N.A.P.M.,Rozier,P.J.C.M.,2001.Feasibility of environment for years.No well-know procedure have been warm drawing of aluminum products.J.Mater.Process developed for press shop.It is very important to transfer warm Technol..115,118-121. forming from lab to press shop.As known sheet metal part Boyd,R.G.,Jung,C.,Seldon,B.J.,1995.The market structure of the manufacturing is a mass production process.It is necessary to US aluminum industry.J.Econ.Bus.47,293-301. develop the procedure for successful warm forming operation Browne,DJ.,Battikha,E.,1995.Optimization of aluminum sheet forming using a flexible die.J.Mater.Process.Technol.55, in press shop. 218-223. The properties of aluminum alloys at elevated tempera- Carle,D.,Blount,G.,1999.The suitability of aluminum as an tures have been determined by various researchers around the alternative material for car bodies.Mater.Des.20,267-272 Please cite this article in press as:Toros,S.,et al.,Review of warm forming of aluminum-magnesium alloys,J.Mater.Process.Tech.(2008), doi10.1016/.jmatprotec..2008.03.057Please cite this article in press as: Toros, S., et al., Review of warm forming of aluminum–magnesium alloys, J. Mater. Process. Tech. (2008), doi:10.1016/j.jmatprotec.2008.03.057 PROTEC-12068; No. of Pages 12 ARTICLE IN PRESS 10 journal of materials processing technology xxx (2008) xxx–xxx ity, and low cost. They also investigated the influence of small additions of Ca and Sr on the tensile and creep properties. Another room temperature formability testing was performed on an Al–Mg6.8 type alloy sheet with a fully recrystallized structure (average grain diameter ∼18m) and after partial annealing with a retained deformed structure by Romhanji et al. (1998). The yield strengths attained after full recrystal￾lization and after partial annealing, were 175 and 283 MPa, respectively. Such an increase in strength is followed by forma￾bility degradation, maximized around the plain strain state to either 42%, as obtained using the limiting dome height test (LDH), or 35% after using forming limit curves (FLC). A com￾parison with known high-strength formable alloys has shown that the tested alloy in the recrystallized condition has a bet￾ter stretch formability (at the same or even higher yield stress level), while in the unrecrystallized-partially annealed con￾dition it has a lower formability, limiting its application to moderate forming requirements for very high-strength parts. 3.3. The effects of lubrication One of the important parameter for the forming of aluminum sheets is lubrication. It is used during the forming process to get better surface quality and to decrease the friction of die surfaces. This contributes to increasing the die life￾time by reducing wear. Meiler et al. (2003) investigated the effects of dry film lubricants on aluminum sheet metal form￾ing and compared the results with other type lubricants. They observed that dry film lubricants showed advantages over con￾ventional oil lubricants because of their high deep drawing performance, especially on complex shaped body panels. They also emphasized in their study the formability is increased as a consequence of reduced friction and it is possible to get more homogeneous sheet thickness distributions. Wu et al. (2006) studied a super plastic 5083 Al alloy under biaxial deformation by deforming the sheet into a rectangular die cavity with and without lubrication. Results indicate that reducing the inter￾facial friction by use of a lubricant altered the metal flow after the deformed sheet had made contact with the die surface. Besides, they observed that changes of the metal flow dur￾ing forming not only developed a better thickness distribution of the formed part, but also improved cavitations distribution (Kelly and Cotterell, 2002). 4. Conclusion In this paper, formability of Al–Mg alloys at warm temperature is presented. In general, at temperatures above 225 ◦C the flow stress becomes strain rate dependent. The warm forming process is beneficial in terms of forma￾bility. Researchers have been conducted their studies at lab environment for years. No well-know procedure have been developed for press shop. It is very important to transfer warm forming from lab to press shop. As known sheet metal part manufacturing is a mass production process. It is necessary to develop the procedure for successful warm forming operation in press shop. The properties of aluminum alloys at elevated tempera￾tures have been determined by various researchers around the world. Many of these researchers have used material prop￾erties which are obtained from tensile test results in their investigations. However, information on properties obtained at elevated temperatures under a biaxial state of stress is limited. Mostly, they are not available for finite element sim￾ulation. This area needs to be studied extensively. In terms of numerical simulations, there are no well defined material models including temperature and strain rate effects for aluminum alloy. Further investigations on material models are required. In future study, material models should be developed and the effect of process parameters should be investigated for process optimization. Acknowledgements This work is supported by The Scientific and Technologi￾cal Research Council of Turkey (TUB¨ ˙ ITAK). Project Number: 106M058, Title: “Experimental and Theoretical Investigations of The Effects of Temperature and Deformation Speed on Formability”. TUB¨ ˙ ITAK support is profoundly acknowledged. references Abedrabbo, N., Pourboghrat, F., Carsley, J., 2007. Forming of AA5182-O and AA5754-O at elevated temperatures using coupled thermo-mechanical finite element models. Int. J. Plast. 23, 841–875. Ahmetoglu, M.A., Kinzel, G., Altan, T., 1997. Forming of aluminum alloys-application of computer simulation and blank holding force control. J. Mater. Process. Technol. 71, 147–151. Altan, T., 2002. Warm forming of aluminum alloys-academic exercise or practical opportunity? Stamping J. 14, 58–59. ASM Metal Handbook, 1988. Volume 14 Forming and Forging. 9th ed. ASM International, Metals Park, Ohio, pp. 791–804. Barlat, F., Lian, J., 1989. Plastic behavior and stretchability of sheet metals. Part I. A yield function for orthotropic sheets under plane stress conditions. Int. J. Plast. 5, 51–66. Barlat, F., Lege, D.J., Brem, J.C., 1991. A six-component yield function for anisotropic materials. Int. J. Plast. 7, 693–712. Barlat, F., Maeda, Y., Chung, K., Yanagawa, M., Brem, J.C., Hayashida, Y., Lege, D.J., Matsui, K., Murtha, S.J., Hattori, S., Becker, R.C., Makosey, S., 1997. Yield function development for aluminum alloy sheets. J. Mech. Phys. Solids 45 (11/12), 1727–1763. Barlat, F., Brem, J.C., Yoon, J.W., Chung, K., Dick, R.E., Lege, D.J., Pourboghrat, F., Choi, S.H., Chu, E., 2003. Plane stress yield function for aluminum alloy sheets. Part 1. Theory. Int. J. Plast. 19, 1297–1319. Barlat, F., Aretz, H., Yoon, J.W., Karabin, M.E., Brem, J.C., Dick, R.E., 2005. Linear transformation-based anisotropic yield functions. Int. J. Plast. 21 (5), 1009–1039. Beer, F.P., Johnston, E.R., 1992. Mechanics of Materials, Second ed. McGraw-Hill, Inc, International ed. Bolt, P.J., Lamboo, N.A.P.M., Rozier, P.J.C.M., 2001. Feasibility of warm drawing of aluminum products. J. Mater. Process. Technol. 115, 118–121. Boyd, R.G., Jung, C., Seldon, B.J., 1995. The market structure of the US aluminum industry. J. Econ. Bus. 47, 293–301. Browne, D.J., Battikha, E., 1995. Optimization of aluminum sheet forming using a flexible die. J. Mater. Process. Technol. 55, 218–223. Carle, D., Blount, G., 1999. The suitability of aluminum as an alternative material for car bodies. Mater. Des. 20, 267–272.