Workshop proceeding - final.pdf - Faculty of Information and ...

Fig. 4 The true stress-strain curves for cast state and ECAPed with 4 passes at different temperatures.
Fig. 5 (a) though (c) showed the OM microstructures of the materials processed at 200, 150 and
100 °C after compression tests and Fig. 5 (d) exhibited the microstructure of the material processed at
room temperature. Fig. 5 demonstrated that there were no twins when the grain size was less than 5
µm, but some twins existed in the grains about 5 µm or larger, as in Fig. 5 (b). Combining this feature
with the compression behaviours in Fig. 4, it might conclude that strain hardening was, at least
partially, attributed to mechanical twining. In addition, the high yield stress and low ductility for the
materials ECAPed at 150 and 100 ˚C may due to formation of texture during the BP-ECAP. Cisar [10]
and Kim [19] etc have reported that ECAP processing makes basal plan parallel to extrusion direction
results in Schmid factor closed to 0, which is also makes yield strength increase and ductility decrease.
Fig. 5 The microstructure of compressive deformed samples: (a) 200 ºC; (b) 150 ºC; (c) 100 ºC; (e)
room temperature (SEM).
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