Simultaneously Enhanced Strength and Ductility of Al–Mg–Si Alloys during Aging Process Induced by Electro-Pulsing Treatment

Most methods used for strengthening metallic materials, such as thermal-mechanical treatment, will sacrifice the ductility. A novel technology, electric pulsing treatment (EPT), is applied to break this trade-off, which produces an Al–Mg–Si alloy with superior ductility and higher strength within only 560 ms. Systematic electron microscopy characterization and finite element simulation reveal that EPT promotes the formation of clusters Mg2(Si,Cu)3 and sub-grain boundaries. The results of quantitative calculation indicate that the dislocation entanglement is delayed due to the existence of clusters and longer dislocation glide distance, so that ultimate strength is fully improved. Moreover, the superior ductility is mainly governed by sub-grains which lead to higher mobile dislocation density, appearance of new crystal orientations, and prevention of crack propagation. Thereupon, this interesting finding paves the way in developing the Al–Mg–Si alloy with higher mechanical properties efficiently.

Influence of Predeformation on Mechanical Behavior of Hastelloy C-276

The accurate prediction of springback is a subject of major concern during the sheet metal forming. In this study, the recovery behavior of Hastelloy C-276 sheet under different amounts of pre-strain has been investigated by uniaxial cyclic tensile tests. The total springback during unloading could be separated into a linear springback and a nonlinear springback. The percentage of nonlinear recovery to the total recovery increased as the pre-strain increased. Both unloading and reloading elastic moduli decreased as the pre-strain increased, which affected the springback phenomenon significantly. Nonlinear recovery could be explained by the movement of dislocations in the reverse direction. The decrease of unloading elastic modulus is mainly related with the dislocation motion and the mobile dislocation density.

Discrete Dislocation Dynamics Simulation on Strengths of Dislocation Network Stacks in Multilayered Structures

Strengths of multilayered structures have been investigated using three-dimensional discrete dislocation dynamics (DDD) simulation. The multilayered structure was modeled as a stack of misfit dislocation networks which must exist at an interface between adjoining crystals having different lattice constants. Passages of a single mobile dislocation through several kinds of network stacks were simulated. The critical stress required for the dislocation passage depended on the dislocation spacing of the network, the number of network sheet and the spacing between network sheets.