*3.3.2 Variation of tensile strength with two different die and processing temperature*

The engineering stress-strain curves of un-ECAPed and ECAPed AZ80/91 Mg alloys at two different dies are shown in **Figure 13**. The stress-strain curves show that ultimate tensile strength and ductility of ECAP-4P processed AZ80 specimens at 598 K are about 489.17 MPa, and 19.03%, respectively for die A, Along with this, the same material processed through die B 4P-ECAP exhibited UTS and %elongation is 451.01 MPa and 11.76% respectively, which are higher than that of an as-received and homogenized specimen of AZ80 Mg alloys. Similarly, the AZ91 Mg alloy processed through die A has greatly improved ultimate tensile strength and ductility. Particularly, as-received AZ91 alloys have 372.74 MPa and 7.84% of UTS and ductility respectively, which is further enhanced to 432.81 MPa and 19.13% after processing through die A for 4 passes and 410.35 MPa and 13.22% of ultimate tensile strength and ductility was observed after processing through die B for 4 passes. From this result, it was found that compared with the ECAPed AZ91 Mg alloys processed with die A, the AZ80 Mg alloy processed through die A exhibited enhanced tensile properties compared to die B. This is due to an induced large amount of plastic strain during ECAP.
