PROTEC-12068:No.of Pages 12 ARTICLE IN PRESS JOURNAL OF MATERIALS PROCESSING TECHNOLOGY XXX (2008)XXX-XXX nd the sheet(Hutchi Cooled Punch e limits an de oped blank holding force (BHF)contro Water Cooling Heat Blank Holder these d part qu Electric Heater Pin Thermocoupl trol afo esaid p meters.Jinta et al (2000) (XX and results indicate that aluminum allo ally forms rinkles then steel,especially 6xxx series alu n allo a 、Drawing Die n deep drawing of square cup in order i Wire Thermocouple tearing,and thickn material to be drawn into the die cavity without line at the straight sides which cause tearing.Lin e 00 Shehata et al.,1978).Schmoeckel (1994)and Schmoeckel et rmined the drawing limit under cor ant 1(1995)investigated the drawability of 5xxx series alloys into the die cavity during the stretch forming of larg pa de that they redu orming showed that the formability with a partial heating ir the 100 ler or matrices are a was mucr ls ts er when co 1994 f dr wbead and the amo ount of force on it are very s of part quality.Samu 2002 investigated the force (DBRP)and BHF numerically and experimentally forau rated hydromechanical stamp.Modeling of the deep draw minum alloy.In his study.two kinds of drawbead geom e bead are higher than those for the rounded femal It was demonstrated that the formability is improved by He emph ncy are o re increase. but the ts ent plastic strain and von Mises stresse on the con mposition of the aluminum afsquarefemaled have a relativ ely goo stretcher lines,which givesan uneven surface after deform The effects of temperatures and strain rates Althoueh the aluminum alloys have hieh-streneth to v eigh at the elevate ratio and good corros esistance.the low formability luminum shee some prod intended to over come this 2002).Yamashita et al.(2007)numer ally si ulated circu levated formingtem cups cal warm forming experimental set-up is shown in Fig6.in waomingset-updies andbl oders are he ated t of the rigid punch.Browne and Battikha(199 eating rods that are located in these narts are used hut ther is a risk of necking during heating and cooling.Warm form o ac urately simulate warm forming of alumi m shee ars,e.g the 1970s and 198 the t d an nk,2004).Because of this, on very impo a出 al for the aluminum alloys such as 5082 the formability of the Al-Mg alloy sheets can be improved by ncreasing the temperature in some parts of the sheet an os.s.et al..Review of warm forming of aluminun magnesium alloys.I.Mater.Process.Tech.(2008)Please 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 6 journal of materials processing technology xxx (2008) xxx–xxx and the local curvature of the sheet (Hutchinson and Neale, 1985). Ahmetoglu et al. (1997) determined wrinkling and frac￾ture limits and developed blank holding force (BHF) control to eliminate these defects, improve part quality and increase the formability. A computer simulation model was developed to control aforesaid parameters. Jinta et al. (2000) examined wrinkle behavior in 5XXX and 6XXX series aluminum alloys and compared the results with wrinkle behavior of steel. Their results indicate that aluminum alloys generally forms more wrinkles then steel, especially 6XXX series aluminum alloy has a tendency to more wrinkles than 5XXX series. Gavas and Izciler (2007) examined the effect of blank holder gap (BHG) on deep drawing of square cup in order to investigate wrin￾kling, tearing, and thickness distribution. As a result of their study, they observed that increasing of the BHG allows more material to be drawn into the die cavity without tearing or shape distortions. It is also noticed that it was impossible to use too large BHG because of excessive wrinkling and buck￾ling at the straight sides which cause tearing. Lin et al. (2007) determined the drawing limit under constant and variable BHF. Drawbeads are directly related with wrinkling behavior of the materials. They are used to control the flow of sheet metal into the die cavity during the stretch forming of large panels. Beside that they reduce the BHF and minimize the blank size needed to make a part (Demeri, 1993). The shape and position of drawbead and the amount of force on it are very impor￾tant in terms of part quality. Samuel (2002) investigated the influence of drawbead geometry on the drawbead restraining force (DBRF) and BHF numerically and experimentally for alu￾minum alloy. In his study, two kinds of drawbead geometry which are square female and round female were investigated. As a result, it is obtained that the DBRF and BHF for the square female bead are higher than those for the rounded female bead. He emphasized that this discrepancy are occurred due to the sharp corners. It is also observed that the total equiva￾lent plastic strain and von Mises stresses at upper and lower surfaces of square female drawbead are higher than those for the round female drawbead. 3.2. The effects of temperatures and strain rates Although the aluminum alloys have high-strength to weight ratio and good corrosion resistance, the low formability of aluminum sheets limits their use in some products with complex shapes, such as automotive body parts. The warm forming process is intended to overcome this problem by using an elevated forming temperature which is below the recrystallization temperature (Tebbe and Kridli, 2004). A typ￾ical warm forming experimental set-up is shown in Fig. 6. In the warm forming set-up, dies and blank holders are heated to 200–300 ◦C. In order to heat dies and blank holders, electrical heating rods that are located in these parts are used but there is a risk of necking during heating and cooling. Warm form￾ing was studied for many years, e.g. in the 1970s and 1980s by Shehata et al. (1978) and Wilson (1988) with increasing atten￾tion being dedicated to the subject in the last decade. The warm forming method improves the formability of the aluminum alloys. This improvement at the elevated tem￾peratures is principal for the aluminum alloys such as 5082 and 5005 alloys due to the increased strain rate hardening Fig. 6 – A typical warm forming set-up (Palumbo and Tricarico, 2007). (Shehata et al., 1978). Schmoeckel (1994) and Schmoeckel et al. (1995) investigated the drawability of 5XXX series alloys at the elevated temperatures. Temperature has a significant influence on the stamping process. Further investigation on forming showed that the formability with a partial heating in the holder or matrices area was much better when compared with the homogeneously heated tools (Schmoeckel, 1994). Schmoeckel et al. (1995) showed that a significant increase in the limiting drawing ratio (LDR) for the aluminum alloy AlMg4.5 Mn0.4 can be achieved by a heated and lower strain rated hydromechanical stamp. Modeling of the deep draw￾ing with a rotationally symmetrical tool (stamp diameter: 100mm) which was cooled from the stamp side by additional air ensured an increase in LDR. It was demonstrated that the formability is improved by a uniform temperature increase, but the best results are obtained by applying temperature gradients. The formabil￾ity depends strongly on the composition of the aluminum alloy. Aluminum–magnesium alloys have a relatively good formability. A disadvantage is that these alloys suffer from stretcher lines, which gives an uneven surface after deforma￾tion. Because of this reason, 5XXX series aluminum is used for inner panels of vehicles. These undesired surface defects can be eliminated by the forming processes at the elevated temperatures (Van Den Boogaard et al., 2001). The aluminum which contains 6% magnesium could give a 300% total elonga￾tion at about 250 ◦C, finds more application in industry (Altan, 2002). Yamashita et al. (2007) numerically simulated circu￾lar cups drawing process by using Maslennikov’s technique (Maslennikov, 1957) which is also called “punchless drawing”. In this production technique, a rubber ring is used instead of the rigid punch. Browne and Battikha (1995) optimized the formability process by using a flexible die and optimized the process parameters to ensure a defect-free product. To accurately simulate warm forming of aluminum sheet, a material model is required that incorporates the temper￾ature and strain-rate dependency (Van Den Boogaard and Huetink, 2004 ´ ). Because of this, the effect of temperature distribution on warm forming performance is very impor￾tant. Van Den Boogaard and Huetink (2006) ´ observed that the formability of the Al–Mg alloy sheets can be improved by increasing the temperature in some parts of the sheet and