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S. S. Nayak et al.
by the activation of a slip-plane, which is determined by the preferred orientation
of crystals [58, 59]. The stability of the slip systems of the materials is dependent
on the Schmid factor. Texture components having high Schmid factor are unstable
under tensile load. Crystals of lower Schmid factor show higher yield strength.
In a single crystal, for a particular slip-plane and slip-direction to applied stress
in a given direction, Schmid factor (cosφ × cosλ) is related to the critically resolved
shear stress (CRSS), where φ and λ are angle made by shear-plane normal and slipdirection with stress axis, respectively. It is useful for FCC polycrystalline materials
to analyse the relationship between tensile strength and texture where lower the
Schmid factor gives both higher yield as well as ultimate tensile strength [60]. Under
the action of stress, materials show lowest value of resistance (i.e. yield strength)
when the slip-plane normal and slip-directions are inclined at an angle of 45° with
direction of an applied force. The value of Schmid factor is 0.5 when the slip-plane
normal and slip-direction are inclined at angle of 45° with stress axis. Schmid factor
of the crystals affects the activation of slip-planes. The Schmid factor values of
Brass, Goss and Rt-Cube textures are 0.2747, 0.4082 and 0.4079, respectively. For
aluminium material, the most favourable grain growth direction is <100> under the
effect of the heat. Another aspect that can describe the effect of texture on various
mechanical properties is the Taylor factor [61].
Taylor factor gives an indication of the resistance to deformation of a particular
point for a given stress state. It is a geometric factor based on the texture of grain
with respect to the applied strain gradient. An FCC material having 100% <111>
texture component would have the highest possible Taylor factor, which would create
a material with the highest tensile strength and with lower Taylor factor would create
a material with lower yield strength. Another aspect is the volume fraction of grains.
The higher the volume fraction of <111> texture in an FCC material, the higher is
the yield strength [62]. Texture has a strong relation with elongation stated in the
introduction. It is also a fact that when a polycrystalline material is subjected to plastic
deformation, hardness increases due to strain hardening. FSW is a process where
plastic deformation takes place. Strength and hardness have a linear relationship.
This provides a way to comment that texture affects hardness and tensile strength.
FSW produces various texture components in the FSWed cross section. For almost
all the metallic alloys, shear textured grains dominate at the SZ and recrystallized
and deformation textured grains at the other weld regions in this process. Intensity
of texture components slightly vary in FSWed regions. FSW also produces shear
texture at the joint line. Similar to FSW, other solid-state welding techniques such
as UW and EW also produce strong shear textured grains at the weld interface
for aluminium alloys [34, 36]. Comparing with FSW, fusion welding techniques
produce weak textured grains. GTAW and LBW produce weak textured grains at
NZ as compared to HAZ [33]. Cube {001} <100> is the dominating recrystallized
texture component in the mentioned fusion welding techniques. The deformation
(i.e. deformation direction and deformation rate) and heat are the two important
parameters which determines the texture components in the weld regions for a given
material.
S. S. Nayak et al.
by the activation of a slip-plane, which is determined by the preferred orientation
of crystals [58, 59]. The stability of the slip systems of the materials is dependent
on the Schmid factor. Texture components having high Schmid factor are unstable
under tensile load. Crystals of lower Schmid factor show higher yield strength.
In a single crystal, for a particular slip-plane and slip-direction to applied stress
in a given direction, Schmid factor (cosφ × cosλ) is related to the critically resolved
shear stress (CRSS), where φ and λ are angle made by shear-plane normal and slipdirection with stress axis, respectively. It is useful for FCC polycrystalline materials
to analyse the relationship between tensile strength and texture where lower the
Schmid factor gives both higher yield as well as ultimate tensile strength [60]. Under
the action of stress, materials show lowest value of resistance (i.e. yield strength)
when the slip-plane normal and slip-directions are inclined at an angle of 45° with
direction of an applied force. The value of Schmid factor is 0.5 when the slip-plane
normal and slip-direction are inclined at angle of 45° with stress axis. Schmid factor
of the crystals affects the activation of slip-planes. The Schmid factor values of
Brass, Goss and Rt-Cube textures are 0.2747, 0.4082 and 0.4079, respectively. For
aluminium material, the most favourable grain growth direction is <100> under the
effect of the heat. Another aspect that can describe the effect of texture on various
mechanical properties is the Taylor factor [61].
Taylor factor gives an indication of the resistance to deformation of a particular
point for a given stress state. It is a geometric factor based on the texture of grain
with respect to the applied strain gradient. An FCC material having 100% <111>
texture component would have the highest possible Taylor factor, which would create
a material with the highest tensile strength and with lower Taylor factor would create
a material with lower yield strength. Another aspect is the volume fraction of grains.
The higher the volume fraction of <111> texture in an FCC material, the higher is
the yield strength [62]. Texture has a strong relation with elongation stated in the
introduction. It is also a fact that when a polycrystalline material is subjected to plastic
deformation, hardness increases due to strain hardening. FSW is a process where
plastic deformation takes place. Strength and hardness have a linear relationship.
This provides a way to comment that texture affects hardness and tensile strength.
FSW produces various texture components in the FSWed cross section. For almost
all the metallic alloys, shear textured grains dominate at the SZ and recrystallized
and deformation textured grains at the other weld regions in this process. Intensity
of texture components slightly vary in FSWed regions. FSW also produces shear
texture at the joint line. Similar to FSW, other solid-state welding techniques such
as UW and EW also produce strong shear textured grains at the weld interface
for aluminium alloys [34, 36]. Comparing with FSW, fusion welding techniques
produce weak textured grains. GTAW and LBW produce weak textured grains at
NZ as compared to HAZ [33]. Cube {001} <100> is the dominating recrystallized
texture component in the mentioned fusion welding techniques. The deformation
(i.e. deformation direction and deformation rate) and heat are the two important
parameters which determines the texture components in the weld regions for a given
material.