The Deformation Behavior, Texture And Microstructure Evolution Of Aluminum Alloy Under Electropulsing

Due to the advantages of the high strength to weight ratio, good corrosion resistance and so on, aluminum alloys are widely used in the important fields of national economy, such as aerospace, automobile industry. However, owing to the interaction between solute atoms and mobile dislocations, the phenomenon of plastic instability will take place when aluminum alloys are deformed at room temperature, i.e. Portevin-Le Chatelier(PLC) effect, which is highly detrimental for mechanical properties and surface quality, therefore, how to avoid the occurrence of PLC effect is the issue we must pay high attention to when aluminum alloys are deformed. As a new method of treatment, electropulsing has attracted enduring attention due to its influence on the microstructures and properties, especially the enhancement of plasticity. However, it still remains to be answered that whether electropulsing could give rise to the variation of the interaction between solute atoms and mobile dislocations, further, affect the PLC effect, texture and microstructure. Based on the above research background, the 5A02 aluminum alloy is selected as the research object. With the following influencing factors-the intensity of electropulsing and strain rate considered, the present work systematically explores the deformation behavior, texture and microstructure evolution of aluminum alloy under electropulsing by adopting the method of uniaxial tensile testing, electron backscattered diffraction(EBSD) and transmission electron microscope(TEM).Firstly, we study the deformation behavior of 5A02 aluminum alloy under electropulsing. Under the constant strain rate, PLC effect is gradually enhanced with the intensity of electropulsing increasing from 0A to 40 A. However, PLC effect is suppressed as the intensity further rises to 50 A. Under the constant intensity of electropulsing, PLC effect is gradually enhanced with the strain rate decreasing from 1×10-2s-1 to 5×10-4s-1. Nevertheless, PLC effect disappears as the strain rate further decreases to 1×10-4s-1. Furthermore, electropulsing promotes the PLC domain to shift to the region of high stain rate. With theoretical calculation and Monte Carlo simulation employed, we deeply explore the effect of intensity of electropulsing and strain rate on the interaction between solute atoms and mobile dislocations, respectively.In addition, texture and microstructure evolution under electropulsing are also taken into consideration. With the intensity of electropulsing rising from 0A to 50 A, the volume fraction of Cube texture gradually increases, accompanied with the reduction of S texture. But strain rate has no obvious effect on the evolution of Cube texture. Based on the theory of oriented nucleation and oriented growth, the influence of intensity of electropulsing on the evolution of Cube texture is discussed. With respect to microstructure evolution, dislocation configurations are characterized by dislocation bands(0A), elongated dislocation cells(20A and 40A) and irregular dislocation cells mixed with dislocation tangle(50A), indicating a transition of slip mode from planar slip to wave slip. With the strain rate increasing from 1×10-4s-1 to 1×10-2s-1, dislocation configurations are characterized by elongated dislocation cells mixed with dislocation tangle and dislocation bands, respectively, suggesting a transition of slip mode from wave slip to planar slip. The mechanism of the transition of slip mode is analyzed in detail on the basis of the effect of the variation of concentration of solute atoms on the joining up of the two partials of screw dislocation.