Size effects on flow stress behavior during electrically-assisted micro-tension in a magnesium alloy AZ31

Abstract

As one of the promising micro-manufacturing technologies, micro-forming has economical and ecological advantages in terms of mass and near-net-shape production. However, size effects increasingly affect material performances with scaling down geometry and process parameters and consequently hinder applications of micro-forming. Electrically-assisted (EA) micro-forming may have the potential to minimize the size effects. In order to investigate the size effects in the EA micro-forming, uniaxial tension tests were conducted on miniaturized AZ31 tensile samples with varying grain sizes and geometry sizes at a constant DC current density. It was found that the normalized flow stress reduction, i.e., decreases of flow stresses / flow stresses at room temperature (RT), increased with the decrease of the grain size and with the increase of the geometry size at the

Investigation of Electrically-Assisted Rolling Process of Corrugated Surface Microstructure with T2 Copper Foil

“…However, the softening effect is weakened when the current is present. This result indicates that the current can weaken the grain size effect, which corresponds to the result of Wang et al [25]. In order to investigate the grain size effect on the EA tension, the EA tensile tests of various grain sizes and N values were carried out, as shown in Figure 3.…”

“…They believed that when the current was applied, the data dispersion would be reduced. Their studies indicated that the current can weaken the size effect [25,26]. Compared with the tensions at room temperature, oven-heated and air-cooled conditions, the fracture stresses were smallest and the fracture strains were largest in the EA tension [27].…”

Investigation of Heterogeneous Joule Heating as the Explanation for the Transient Electroplastic Stress Drop in Pulsed Tension of 7075-T6 Aluminum

“…The grain boundary thickness (t gb ) was determined using Eq. (7) [38], where k is a material constant and d g is the grain size (9 lm), k was set to a midpoint value equal to 0.125 [17]. Other values of k were created around the midpoint to study the effect of grain boundary thickness, shown in Table 4.…”

“…It has been shown that in steady-state circumstances, the electroplastic effect can be fully modeled and predicted using a conventional energy balance and thermal softening approach that assumes 100% bulk (homogeneous) Joule heating [9,10]. These works use electricity to heat a part but allow the temperature to stabilize before starting deformation.The steady-state modeling approach implemented into a finite element analysis (FEA) cannot predict the transient stress drop caused by pulsed electric current even though the correct temperature profile is predicted [11][12][13].Experimental results comparing the flow stress results of specimen heated in a furnace to the same temperatures seen through electrically assisted deformation found that electrically assisted deformation had a lower stress than thermally assisted, suggesting bulk Joule heating cannot fully explain the transient electroplastic effect [7,[14][15][16][17][18]. Theories have been developed to explain the transient nature of the electroplastic effect; these include (a detailed review of electroplastic theories and models can be found in Ref.…”

“…Experimental results comparing the flow stress results of specimen heated in a furnace to the same temperatures seen through electrically assisted deformation found that electrically assisted deformation had a lower stress than thermally assisted, suggesting bulk Joule heating cannot fully explain the transient electroplastic effect [7,[14][15][16][17][18]. Theories have been developed to explain the transient nature of the electroplastic effect; these include (a detailed review of electroplastic theories and models can be found in Ref.…”