Electrically-Assisted Forming of Magnesium AZ31: Effect of Current Magnitude and Deformation Rate on Forgeability

Abstract

Currently, the automotive and aircraft industries are considering increasing the use of magnesium within their products due to its favorable strength-to-weight characteristics. However, the implementation of this material is limited as a result of its formability. Partially addressing this issue, previous research has shown that electrically-assisted forming (EAF) improves the tensile formability of magnesium sheet metal. While these results are highly beneficial toward fabricating the skin of the vehicle, a technique for allowing the use of magnesium alloys in the production of the structural/mechanical components is also desirable. Given the influence that FAF has already exhibited on tensile deformation, the research herein focuses on incorporating this technique within compressive operations. The potential benefit of using FAF on compressive processes has been demonstrated in related research where other ntaterials, such as titanium artd aluminum, have shown improved compressive behavior. Therefore, this research endeavors to amalgamate these findings to Mg AZ31B-0, which is traditionally hard to forge. As such, to demonstrate the effects of FAF on this alloy, two series of tests were petformed. First, the sensitivity of the alloy to the FAF process was determined by varying the current density and platen speed during an upsetting process (flat dies). Then, the ability to utilize impression (shaped) dies was examined. Through this study, it was shown for the first time that the FAF process increases the forgeability of this magnesium alloy through improvements such as decreased machine force requirements and increased achievable deformation. Additionally, the ability to form the desired final specimen geometry was achieved. Furthermore, this work also showed that this alloy is sensitive to any deformation rate changes when utilizing the FAF process. Last, a threshold current density was noted for this material where significant forgeability improvements could be realized once exceeded.

Effect of pulsed current on the deformation behavior of AZ31B magnesium alloy

“…One of the methods is the application of magnesium alloy while it has a high specific strength but with a low formability, which limits its application [1,2]. Although the relatively high deformation temperature greatly improves the plasticity of magnesium alloy, hot deformation has many drawbacks such as the increase of thermal stress, the coarse surface, the high expense of energy, the weak dimensional accuracy and the decreased strength of the die [1,3] etc.…”

Decoupling Thermal and Electrical Effect in an Electrically Assisted Uniaxial Tensile Test Using Finite Element Analysis

“…[9,10] The interest in electroplasticity has gained much interest of late [11][12][13][14][15][16] in the potential application of enhancing formability [7] and reducing spring-back [17] in sheet metal components. The application is especially useful in materials such as magnesium, [18] titanium, [19] and certain aluminum alloys, [15] which exhibit poor formability at room temperature. The warm forming which is generally required for such alloys can be replaced by electrically assisted forming.…”

A review of electrically-assisted manufacturing

“…7. Jones et al 70 also reported that the forgeability was significantly increased as the continuous electric current increased. The ability to form a final geometry, which is not achievable at room temperature, was achievable in the EA forging process.…”