Dynamic Tensile Deformation of High Strength Aluminum Alloys Processed Following Novel Thermomechanical Treatment Strategies

Weidig

et al. 2020

Metals

Self Cite

This study focuses on the high temperature characteristics of thermo-mechanically processed AA7075 alloy. An integrated die forming process that combines solution heat treatment and hot forming at different temperatures was employed to process the AA7075 alloy. Low die temperature resulted in the fabrication of parts with higher strength, similar to that of T6 condition, while forming this alloy in the hot die led to the fabrication of more ductile parts. Isothermal uniaxial tensile tests in the temperature range of 200–400 °C and at strain rates ranging from 0.001–0.1 s−1 were performed on the as-received material, and on both the solution heat-treated and the thermo-mechanically processed parts to explore the impacts of deformation parameters on the mechanical behavior at elevated temperatures. Flow stress levels of AA7075 alloy in all processing states were shown to be strongly temperature- and strain-rate dependent. Results imply that thermo-mechanical parameters are very influential on the mechanical properties of the AA7075 alloy formed at elevated temperatures. Microstructural studies were conducted by utilizing optical microscopy and a scanning electron microscope to reveal the dominant softening mechanism and the level of grain growth at elevated temperatures.

Section: Conditions Yield Strength (Mpa) Ultimate Tensile Strength (Mmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties

Sajadifar

Weidig

et al. 2020

Metals

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Section: Characterization Of Properties and Local Deformation Behaviormentioning

confidence: 99%

Section: Characterization Of Properties and Local Deformation Behaviormentioning

confidence: 99%

Characterization of Mechanical Properties, Macroscopic Deformation Behavior, and Microstructure of Functionally Graded 22MnB5 Steel

Schade

Ademaj³

et al. 2021

steel research int.

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The ongoing global trend toward carbon dioxide emission reduction forced the automotive industry to design lighter and resource-efficient vehicle bodies, leading to the huge success of the press hardening process. [1][2][3][4][5] One reason for this success lies in the availability of thin-walled ultrahigh strength steel 22MnB5, which combines good formability and highest strength properties of 1500 MPa at a fully martensitic structure after press hardening at reasonable costs. [6,7] Since the first application in the automotive industry in 1986 as a side-impact beam, [8] the application field of 22MnB5 components increases continuously from B-pillar to roof rail reinforcement and other parts to enhance passenger safety. [9,10] The thermomechanical approach of press hardening allows the production of complex-shaped components with high dimensional accuracy, [11] excellent mechanical properties, and, at the same time, offers the opportunity for realizing tailored properties. [12,13] Although a time-temperature course of uniform austenitization and quenching in a cooled forming tool, Figure 1a, results in a homogenous fully martensitic structure with highest strength, a locally varying time-temperature course during the forming process, Figure 1b, enables the creation of a tailored distribution of microstructures, where mechanical properties are locally adjusted to perfectly meet the load profile, e.g., in case of crash-relevant components. [5,6] According to Ademaj et al., after uniform austenitization at 930 C but differential cooling of 22MnB5, zones following "route H" develop highest tensile strengths (1500 MPa) whereas zones following "route S" show lower tensile strength properties (614 MPa). [14] Both process strategies of Figure 1 are chosen for the current study with respect to the aforementioned investigations.This approach has been identified as a viable option to obtain lighter body structures through the ability to design load adapted structures and to combine contradictory requirements within one component. [14,15] A prominent example in car body structures is the B-pillar, in which the bottom section exhibits higher

“…The main experimental setup in the present study consisted of a roller hearth furnace for solutionizing the sheet material and a hydraulic press (MAE DE Erkrath, Germany, 400 Z 160) with a press capacity of 4000 kN equipped with hat-shaped forming tools. For the artificial aging treatment, a chamber furnace (ThermConcept, Bremen, Germany, KM 710/13) was used to achieve a homogeneous temperature distribution (Figure 1a) [33,34].…”

Section: Experimental Setup and Programmentioning

confidence: 99%

Influence of Hot Deformation on the Precipitation Hardening of High-Strength Aluminum AA7075 during Thermo-Mechanical Processing

Shoshmina

Biegler

et al. 2021

Metals

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The aim of this work was to investigate the effect of hot deformation on the aging behavior of precipitation-hardenable aluminum alloy AA7075 within a novel thermo-mechanical forming process, in order to gain insight into its precipitation kinetics. For this purpose, the material was formed at 420 °C after undergoing solution treatment to different strain levels ranging from 2% to 10% to obtain different dislocation densities. After undergoing hot deformation, aging at 120 °C with different parameters was carried out to improve the material hardness. The resulting material properties and microstructure evolution were characterized afterward using hardness measurements and a transmission electron microscope (TEM). TEM investigations revealed the formation of very fine particles for the material formed at 2%, as well as at 10%, of formed material, which act as effective barriers to dislocation motion. It was found that the response of artificial aging on the deformation degree in hot forming was less than expected due to the thermally activated mechanisms, leading to a decrease in dislocation density. Therefore, a dramatic increase in material hardness with the increase in hot deformation was not observed.