PSI - Issue 21

Nathaniel Mupe et al. / Procedia Structural Integrity 21 (2019) 73–82 Mupe et al./ Structural Integrity Procedia 00 (2019) 000 – 000

80

8

Fig. 7. NTE processed AZ31 tensile test: (a) true stress-strain curve; (b) yield and ultimate tensile strengths; (c) total elongation.

Table 2. Comparative analysis of results of various SPD methods on AZ31 alloy Reference Method Equivalent strain, ε Temperature (K)

Grain size, µm d -0.5

Hardness (Hv) UTS (Mpa) Yield (MPa)

Huang et al. (2013)

0

10

0.32 0.03 0.03 0.32 0.03 0.02 0.06 0.25 0.67 0.82 0.06 0.25 0.40 0.56 0.21

55

373

0.6

1030 930 1500 3000 250 10

100 115

HPT

3 0 3 0 0 2 4 0 0 2 4 0 1 2 3 4 0 4 8

55 85 70 57 62 75 88 57 62 63 71 68

473

0.6

Bryla et al. (2012)

218 218 300 360 218 218 280 340 275 280 280 275 255

75 75

As cast Hot rolled ECAP Bc 90/0

623 423 423 623 523 523

16 2.2 1.5 250 16 6.2 3.2 22

175 190

75 75

130 150 200 195 180 175 135

Xia et al. (2005)

473

10

0.32

ECAP Bc 90/0

3

0.58 0.21 0.85 1.00

77 68 77

22 1.4

423

1

77.5

4.3. Comparison of mechanical properties by other SPD methods The behaviours of hardness, yield strength and tensile stress were partly influenced by pressing temperatures and texture orientation. According to Yang et al. (2005) the evolution of refined grains in Mg may occur even though the deformation texture hardly changes. At 373 K and 473 K the basal slip 〈 〉 and glide twinning facilitates accommodation of shear stresses thus limiting significant changes of the orientation between c-axis and extrusion axis. The grains whose c-axis was tilted at angles higher than 10° attributed deformations [Knauer et al. (2013)]. At 523 K the grains whose c-axis orientation was approximately 10° from the extrusion axis had stable orientation and facilitated shear deformation during pressing since shear direction and c-axis were almost perpendicular. This promoted shear deformation through the dislocation at basal slip 〈 〉 and eventually increased the YS and UTS after