Figure 3 Representative true stress-true strain curves for both
[100] and [110] Mo in (a), Mo-5Re in (b), Mo-14Re in (c) and
Mo-42Re in (d).
True stress-true strain curves of [110] and [100] Mo-5Re
coincide in elastic region, as shown in Figure 3(b). [110] Mo-5Re
and [100] Mo-5Re both yield at true stress ~300MPa
that lower than Mo, suggesting softening effect happens in Mo-5Re. After
yield, true stress in [100] Mo-5Re gradually rises from 300MPa to
~600MPa as true strain reaches 2.5%. Then, stress drops
from ~600MPa to ~300MPa at strain 5%.
Whereas, [110] Mo-5Re maintains flow stress at
~400MPa from yield point to 7.5% strain. As strain
higher than 10%, stress fluctuations emerge strongly in both [100]
and [110] Mo-5Re.
Figure 3c shows mechanical responses of [100] and [110] Mo-14Re.
The yield stress in [110] Mo-14Re is higher than in [100]
Mo-14Re, which is differ with Mo and Mo-5Re. The true stress in
[110] Mo-14Re is always higher than in [100] Mo-14Re from yield
point to 25%. It is noted that stress drop behaviors are much less
distinct in Mo-14Re than in Mo and Mo-5Re, showing the plastic
deformation in Mo-14Re is more stable than in Mo-5Re and Mo. What is
more, true stress gradually increases from strain 2.5% to 25% in both
[110] and [100] Mo-14Re, expect for a slight stress drop from
600MPa to 500MPa. The final stress reaches 1200MPa in [110] Mo-14Re,
and 800MPa in [100] Mo-14Re at strain ~25%.
The true stress-true strain curves of [100] and [110] Mo-42Re
are shown in Figure 3d. The stress in [110] Mo-42Re is higher than
in [100] Mo-42Re at yield point. The stress in [110] Mo-42Re
maintains at steady level from 1% to 5%. While in this region, the
stress in [100] Mo-42Re rises from 450MPa to 750MPa. Two curves
overlap within 7.5% to 15%, as shown in the white dotted square in
Figure 3d. As strain continually increases, the stress in [110]
Mo-42Re rapidly enhances to 2000MPa from 15% to 25%. The stress in
[100] Mo-42Re, however, steadily rises to 1200MPa. The stress drops
behaviors in Mo-42Re is much smoother than in Mo-14Re.
Figure 4a shows the results for Mo, Mo-14Re and Mo-42Re with [100]
orientation. Yield strength enhances with Re content rises. Besides, the
stress at 25% strain is effectively improved in [100] Mo-42Re,
which means strong hardening effect. An outstanding feature is that
stress drop behaviors weaken as Re content increases, both in samples
with [100] orientation (Figure 4a) and with [110] orientation
(Figure 4b). The stresses are adjacent in [110] Mo-14Re and Mo-42Re
in the stain region between 2% to 10%. As strain higher than 15% in
[110] samples, stresses in Mo and Mo-42Re begin to rapidly
increases. Such a behavior may be induced via large changing shape of
samples.
Figure 4 The true stress-true strain curves of Mo, Mo-14Re and Mo-42Re
with [100] orientation in (a) and with [110] orientation in (b).
(c) is the summary of yield stresses.
Figure 5 shows the surface micrographs of samples after compression with
true strain 25%. Only one group of parallel slip bands emerge in
[100] Mo and Mo-14Re, as shown in Figure 5a and 5c. [110] Mo
still behaviors strong slips along a single slip plane. Two groups of
slips bands tangles in [100] Mo-42Re, which may lead to
strengthening effect. Plastic deformation in [110] Mo-14Re and
Mo-42Re are dominated by multi-slip bands. Asymmetric deformation leads
inclination in [100] Mo-42Re, as seen in Figure 5e.