**2. Aluminum alloy behavior during hot forming**

Hot forming of aluminum alloys is extensively used in the modern industry and has been explored by many researchers and scientists. The main intension to derive this process is to reduce in-flow stress, increase ductility, reduce work hardening, increase toughness of the material, etc. Furthermore, temperatures lower than those involved during hot forging make easier the obtaining of close tolerances and high surface finish [1]. To lead the hot forming process on different aluminum alloys, different process parameters were considered and the attachable results to the literature were derived.

For details, high-temperature tensile deformation of AA 6082-T4 was experimented in the temperature range of 623–773 K at several strain rates in the range of 5 × 10<sup>−</sup><sup>5</sup> to 2 × 10<sup>−</sup><sup>2</sup> s<sup>−</sup><sup>1</sup> . By this, stress exponent n of 7 during the ranges of temperatures and strain rates was tested. This is higher than what is usually observed in Al-Mg alloys under similar experimental conditions. Improvement in the strain exponent of any material leads to better formability [2]. Hot compression tests were performed on aluminum alloys 7150 and 2026 by varying the temperature from 300°C to 450°C and at a strain rate from 0.01 s<sup>−</sup><sup>1</sup> to 10 s<sup>−</sup><sup>1</sup> [3, 4]. Also, on AA 7075-T6 and AA 7085 aluminum alloy [5, 6] tested at different temperatures and strain rates (450, 500, 520, 550, 580°C and 0.004, 0.04 and 0.4 s <sup>−</sup><sup>1</sup> for AA 7075 and AA 7085 in the temperature range from 250°C to 450°C and at strain rate from 0.01 s<sup>−</sup><sup>1</sup> to 10 s −1 using Gleeble-1500 system, whereas hot deformation behavior was studied on aluminum alloys consisting of Al–6.2Zn–0.70Mg–0.3Mn–0.17Zr with temperature range of 623–773 K and strain rate of 0.01–20 s<sup>−</sup><sup>1</sup> [7]. Using the metallographic and transmission electron microscope, structural changes were studied. The results showed that the true stress-true strain curves exhibit a peak stress at a critical strain, after which the flow stresses decrease monotonically until high strains. The peak stress level decreases with increasing deformation temperature and decreasing strain rate. Similarly, Ag-containing 2519 aluminum alloy hot deformation behaviors were studied by isothermal compression at 300–500°C with strain rates from 0.01 to 10 s<sup>−</sup><sup>1</sup> . Consequences indicated that by increasing the strain rate and decreasing the deformation temperature, the flow stress of the alloy increased. And also, at a strain rate lower than 10 s<sup>−</sup><sup>1</sup> , the flow stress increases with increasing strain until the stress reached the peak value, and later on, a constant flow stress was noted [8]. Aluminum alloy of grade 7075 sheets fabricated by twin roll casting and deformation behavior was investigated at high temperature. At high temperatures from 350 to 500°C and strain rates from 1 × 10<sup>−</sup><sup>3</sup> to 1 × 10<sup>−</sup><sup>2</sup> s<sup>−</sup><sup>1</sup> , hot tensile test was performed. The results showed that by increasing the strain rate and decreasing deformation temperature, flow stress was increased [9]. Similarly, three aluminum alloys containing different silicon contents were studied at a temperature range of 573–773 K with strain rates of 0.01, 0.1, 1 and 5 s<sup>−</sup><sup>1</sup> [10].

Hot deformation behavior using processing map technique of stir cast 7075 alloy was studied. Based on the values of a dimensionless parameter like an efficiency index of energy dissipation, mapping was understood in terms of microstructural processes. Under the temperature and strain rate conditions, the processing map exhibited one distinct domain without any unstable flow conditions. In the processing map, the dynamic recrystallization zone and instable zones were identified. The processing maps can be used to select optimum strain rates and temperatures for effective hot deformation of 7075 alloy [11].

**153**

*Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

Elevated temperature and strain rate were aimed by stamping of AA5083 sheet components. To evaluate mechanical properties and forming behavior, tensile and Nakajima-type tests were carried out. The material flow stress, ductility, and fracture limit sensitivity to temperature and strain rate were evaluated. And also, the optimal combination of process parameters for maximum formability and effective post-deformation mechanical properties were determined [12]. A special device was developed to investigate the hot forming-quenching integrated process of cold-rolled 6A02 aluminum alloy sheet. The strengthening effect was replicated by hardness and uniaxial tensile tests. Microstructure examination was also conducted to clarify the strengthening mechanism. Results showed that hardness increases with solution time increase, and improves significantly after artificial aging. The faster the cooling rate, the greater the strengthening effect. On the same alloy, hot forming-quenching integrated process at different temperatures from 50 to 350°C was investigated. Results showed that the Vickers hardness and tensile strength decreased with increasing forming-dies temperature. To obtain enough strengthening effect, the forming-dies temperature should not be more than 250°C [13]. Springback and microstructure of the final products were analyzed and mechanical properties of the material were measured by tensile tests. The results show that HFSC can improve the formability of AA2024 aluminum alloy. After natural aging for 96 h at room temperature, the products were subjected to the hot bending process with synchronous cooling exhibiting a significant increase in strength. Springback of the aluminum alloy AA5754 under hot stamping conditions was characterized under stretch and pure bending conditions. It was found that elevated temperature stamping was beneficial for springback reduction, at hot dies [14, 15]. Hot stamping was developed for aluminum alloy to improve formability and avoid thermal distortion by combining hot forming and quenching. The effects of heating temperature on formability and strengthening of a solution treated with Al-Mg-Si alloy sheet, uniaxial tensile test, deep drawing test, and free bulging test were carried out at temperatures ranging from 25 to 500°C. It was observed that when temperature was raised to 400°C, the fracture strain and limiting bulging height were increased, whereas the limiting drawing ratio increased as temperature elevated to 200°C and declined subsequently. The mechanical property hardness was changed by increasing temperature and at 200 and 500°C, two peak hardness values were noted. Enhanced formability and strength were obtained simultaneously at 200 and 500°C, either of which can be chosen as appropriate forming temperatures for hot stamping [16]. At different solution heat treatment (SHT) temperatures, SHT time and lubricant stamping experiments were performed with 6061 and 7075 aluminum alloy sheets to investigate the formability and lubrication off a B-pillar. After trimming precision level, forming detections were also carried out. From these observations, the B-pillar wrinkled badly and cracked or even

broke into pieces in cold stamping with or without lubricants [17].

For AA 6061 tailor rolled blanks (TRBs), an integrated hot forming and heat treatment process was proposed to improve the formability and dimensional accuracy. The experimentation of this process for sheet forming of Al6061 TRB was evaluated by performing the Erichsen and V-bending tests. The integrated hot forming and heat treatment process was also compared with the conventional forming method in terms of formability, dimensional accuracy, and mechanical properties [18]. A hot AA6082 specimen and cold P20 tools were studied as a function of contact pressure, specimen thickness, and lubricant, using the inverse FE simulation method for the interfacial heat transfer coefficient (IHTC) evolutions. To predict IHTC evolutions with reductions of different lubricants of sliding distance at different contact pressures and sliding speeds as a function, an interactive model was developed. The interaction between the lubricant and IHTC was deducted such

#### *Aluminum Alloys Behavior during Forming DOI: http://dx.doi.org/10.5772/intechopen.86077*

*Aluminium Alloys and Composites*

the literature were derived.

to 2 × 10<sup>−</sup><sup>2</sup>

at a strain rate from 0.01 s<sup>−</sup><sup>1</sup>

580°C and 0.004, 0.04 and 0.4 s

from 250°C to 450°C and at strain rate from 0.01 s<sup>−</sup><sup>1</sup>

at 300–500°C with strain rates from 0.01 to 10 s<sup>−</sup><sup>1</sup>

s<sup>−</sup><sup>1</sup>

5 × 10<sup>−</sup><sup>5</sup>

of 0.01–20 s<sup>−</sup><sup>1</sup>

processes on various aluminum alloys. Specifically, the hot forming process, deep drawing process, incremental forming process, tube hydroforming process, and

Hot forming of aluminum alloys is extensively used in the modern industry and has been explored by many researchers and scientists. The main intension to derive this process is to reduce in-flow stress, increase ductility, reduce work hardening, increase toughness of the material, etc. Furthermore, temperatures lower than those involved during hot forging make easier the obtaining of close tolerances and high surface finish [1]. To lead the hot forming process on different aluminum alloys, different process parameters were considered and the attachable results to

For details, high-temperature tensile deformation of AA 6082-T4 was experimented in the temperature range of 623–773 K at several strain rates in the range of

tures and strain rates was tested. This is higher than what is usually observed in Al-Mg alloys under similar experimental conditions. Improvement in the strain exponent of any material leads to better formability [2]. Hot compression tests were performed on aluminum alloys 7150 and 2026 by varying the temperature from 300°C to 450°C and

num alloy [5, 6] tested at different temperatures and strain rates (450, 500, 520, 550,

tem, whereas hot deformation behavior was studied on aluminum alloys consisting of Al–6.2Zn–0.70Mg–0.3Mn–0.17Zr with temperature range of 623–773 K and strain rate

structural changes were studied. The results showed that the true stress-true strain curves exhibit a peak stress at a critical strain, after which the flow stresses decrease monotonically until high strains. The peak stress level decreases with increasing deformation temperature and decreasing strain rate. Similarly, Ag-containing 2519 aluminum alloy hot deformation behaviors were studied by isothermal compression

increasing the strain rate and decreasing the deformation temperature, the flow

increases with increasing strain until the stress reached the peak value, and later on, a constant flow stress was noted [8]. Aluminum alloy of grade 7075 sheets fabricated by twin roll casting and deformation behavior was investigated at high temperature. At

tensile test was performed. The results showed that by increasing the strain rate and decreasing deformation temperature, flow stress was increased [9]. Similarly, three aluminum alloys containing different silicon contents were studied at a temperature

Hot deformation behavior using processing map technique of stir cast 7075 alloy was studied. Based on the values of a dimensionless parameter like an efficiency index of energy dissipation, mapping was understood in terms of microstructural processes. Under the temperature and strain rate conditions, the processing map exhibited one distinct domain without any unstable flow conditions. In the processing map, the dynamic recrystallization zone and instable zones were identified. The processing maps can be used to select optimum strain rates and temperatures for

stress of the alloy increased. And also, at a strain rate lower than 10 s<sup>−</sup><sup>1</sup>

high temperatures from 350 to 500°C and strain rates from 1 × 10<sup>−</sup><sup>3</sup>

range of 573–773 K with strain rates of 0.01, 0.1, 1 and 5 s<sup>−</sup><sup>1</sup>

effective hot deformation of 7075 alloy [11].

[7]. Using the metallographic and transmission electron microscope,

. By this, stress exponent n of 7 during the ranges of tempera-

to 10 s<sup>−</sup><sup>1</sup> [3, 4]. Also, on AA 7075-T6 and AA 7085 alumi-

 to 10 s −1

<sup>−</sup><sup>1</sup> for AA 7075 and AA 7085 in the temperature range

using Gleeble-1500 sys-

, the flow stress

 s<sup>−</sup><sup>1</sup> , hot

to 1 × 10<sup>−</sup><sup>2</sup>

. Consequences indicated that by

[10].

stretching process are discussed on different aluminum alloys.

**2. Aluminum alloy behavior during hot forming**

**152**

Elevated temperature and strain rate were aimed by stamping of AA5083 sheet components. To evaluate mechanical properties and forming behavior, tensile and Nakajima-type tests were carried out. The material flow stress, ductility, and fracture limit sensitivity to temperature and strain rate were evaluated. And also, the optimal combination of process parameters for maximum formability and effective post-deformation mechanical properties were determined [12]. A special device was developed to investigate the hot forming-quenching integrated process of cold-rolled 6A02 aluminum alloy sheet. The strengthening effect was replicated by hardness and uniaxial tensile tests. Microstructure examination was also conducted to clarify the strengthening mechanism. Results showed that hardness increases with solution time increase, and improves significantly after artificial aging. The faster the cooling rate, the greater the strengthening effect. On the same alloy, hot forming-quenching integrated process at different temperatures from 50 to 350°C was investigated. Results showed that the Vickers hardness and tensile strength decreased with increasing forming-dies temperature. To obtain enough strengthening effect, the forming-dies temperature should not be more than 250°C [13].

Springback and microstructure of the final products were analyzed and mechanical properties of the material were measured by tensile tests. The results show that HFSC can improve the formability of AA2024 aluminum alloy. After natural aging for 96 h at room temperature, the products were subjected to the hot bending process with synchronous cooling exhibiting a significant increase in strength. Springback of the aluminum alloy AA5754 under hot stamping conditions was characterized under stretch and pure bending conditions. It was found that elevated temperature stamping was beneficial for springback reduction, at hot dies [14, 15]. Hot stamping was developed for aluminum alloy to improve formability and avoid thermal distortion by combining hot forming and quenching. The effects of heating temperature on formability and strengthening of a solution treated with Al-Mg-Si alloy sheet, uniaxial tensile test, deep drawing test, and free bulging test were carried out at temperatures ranging from 25 to 500°C. It was observed that when temperature was raised to 400°C, the fracture strain and limiting bulging height were increased, whereas the limiting drawing ratio increased as temperature elevated to 200°C and declined subsequently. The mechanical property hardness was changed by increasing temperature and at 200 and 500°C, two peak hardness values were noted. Enhanced formability and strength were obtained simultaneously at 200 and 500°C, either of which can be chosen as appropriate forming temperatures for hot stamping [16]. At different solution heat treatment (SHT) temperatures, SHT time and lubricant stamping experiments were performed with 6061 and 7075 aluminum alloy sheets to investigate the formability and lubrication off a B-pillar. After trimming precision level, forming detections were also carried out. From these observations, the B-pillar wrinkled badly and cracked or even broke into pieces in cold stamping with or without lubricants [17].

For AA 6061 tailor rolled blanks (TRBs), an integrated hot forming and heat treatment process was proposed to improve the formability and dimensional accuracy. The experimentation of this process for sheet forming of Al6061 TRB was evaluated by performing the Erichsen and V-bending tests. The integrated hot forming and heat treatment process was also compared with the conventional forming method in terms of formability, dimensional accuracy, and mechanical properties [18]. A hot AA6082 specimen and cold P20 tools were studied as a function of contact pressure, specimen thickness, and lubricant, using the inverse FE simulation method for the interfacial heat transfer coefficient (IHTC) evolutions. To predict IHTC evolutions with reductions of different lubricants of sliding distance at different contact pressures and sliding speeds as a function, an interactive model was developed. The interaction between the lubricant and IHTC was deducted such

that it had three stages such as stage I: the lubricant is applied excessively and the IHTC is plateaued, stage II: in which the lubricant diminishes during sliding and the IHTC decreases, and stage III: lubricant breakdown occurs and the IHTC is equal to its values under dry conditions [19].
