Inhomogeneity Through Warm Equal Channel Angular Pressing

An electron back-scattered diffraction study on the microstructure evolution of severely deformed aluminum AI6061 alloy

“…The strong dependence on the number of passes is obvious. The gradual refinement of the deformed structure and the generation of higher angle boundaries observed with increasing number of passes are consistent with what has been observed in many other studies [5][6][7][8]. At temperature of 100 ºC and two passes, the long grains in the direction of 45º are detectable.…”

“…3(a) and 3(b) the subgrain evolved more rapidly into arrays of high-angle boundaries when the sample was undergone two more passes. In newly evolved grains, further deformation may trigger subgrain formation by slip and lattice rotation, revealed as a distinct local orientation gradient [5]. The microstructures shown in Fig.…”

“…Moreover, these grains are more granular and homogenous. At 200 ºC some other mechanisms like dynamic ageing restricts the grain refining by impeding the dislocations movement [5]. The typical orientation imaging microscopy (OIM) patterns and boundary maps of the grains relating to the forgoing conditions are shown in Fig.…”

“…3(c) and 3(d), at 200 ºC the dominant texture is between <111> and <101> while at 150 ºC there is a random texture. Further deformation leads to increasing the misorientation and formation of new high-angle grain boundaries and grain fragmentation depend on grain orientation [5]. It has been suggested that combination of dynamic ageing and ECAP promotes grain refinement because the more heavily strained grains are constrained by precipitates nucleating between and inside the grains after each pass [12].…”

“…When the sample is pressed through several sequential passes, the shearing characteristics may be changed by rotating the sample between each pass. Thus, the route with which the sample was re-entered to the ECAP die in each pass has an influence on the microstructure achieved due to successive change of the shear plane [5]. Compared to conventional techniques, ECAP offers a large variety of parameters for controlling the microstructure and otherwise the initial microstructure has played a limited role on microstructure orientations [6].…”