A modified counterpart of cyclic extrusion-compression: Experimental study and dislocation density-based finite element modeling

Abstract

In this study, strip cyclic extrusion-compression was introduced as a modified counterpart of cyclic extrusion-compression process for producing ultrafine grained strips. The strip cyclic extrusion-compression method was applied to the pure aluminum and mechanical properties of the processed strips were investigated. The ultrafine grained strips were successfully processed by applying two cycles of strip cyclic extrusion-compression. The transmission electron microscopy observations revealed that the initial microstructure was refined to 1 µm and 650 nm after the first and second cycles, respectively. The yield strength was increased 3 times and the ultimate strength was enhanced 1.5 times after the application of two cycles. The microhardness of the processed strips was increased to 46 Hv and 58 Hv after the first and second cycles, respectively. Furthermore, the fatigue tests revealed that the fatigue strength was higher in the strip cyclic extrusion-compression processed material than the un-processed one. The microstructure evolution during strip cyclic extrusion-compression was also modeled by means of a dislocation density-based finite element method. The finite element method model predicted that the microstructure was refined to 950 nm and 690 nm after the first and second cycles, respectively.