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Remanufacturing and Advanced Machining
size of this zone varies from several micrometers to millimeters dependent
on the material and transition from the SZ to the TMAZ is usually not
sharp. Soft metals, e.g., aluminum and magnesium, have wider zones compared to harder materials such as steel and titanium.
3. Heat-affected zone (HAZ) is placed between TMAZ and base material.
This zone experiences no strain and is subjected to only thermal cycles
which can lead to some grain growth. Mechanical properties in HAZ are
poor, causing failures during tensile tests.
The zones exist on both the advancing and the retreating side; however, they may
not have the same width on either side. The size of each zone depends on a number
of process parameters.
Single-pass FSP comprises a tool that travels in a selected area only once, but if
the tool is traversed again in the same or reverse direction on a previously processed
area, wholly or partially, then it is referred to as “multi-pass FSP.” Harwani et al.
(2021) underline that multi-pass FSP can furnish grain size reduction and texture
weakening more than single-pass processing due to cumulative strain rates in the
successive passes and also enhances the homogeneous distribution of grains in the
material. In fact, FSP performs selective superplastic forming in desired regions.
Gangil et al. (2021) describe FSP as a technique for strengthening of high specific
strength alloys, including age-hardened aluminum alloys, for several industrial
applications through surface composite fabrication, where friction stir processing
generates reinforcement particles.
Węglowski (2018) points out that FSP, like other FSW techniques, can be carried
out using both specialized and typical milling machines. The former are equipped
with dedicated measurement systems, whereas the latter need a universal measurement head. However, milling machines generally fail to provide ideal conditions for
FSP due to an important issue of independent measurement systems development.
The ability of FSP and FSW to provide improved microstructural and mechanical
properties by the grain refining process has given rise to an alternative method of
solid-state (non-melting) process named friction stir-based additive manufacturing
(FSAM) (Srivastava et al., 2021). The process has many benefits, such as solid-state
nature, wrought microstructural properties, flexibility in material feed, and capability to process almost any type of metals and alloys. Due to low temperatures, FSAM
can produce components with negligible porosity, inclusions, particle segregation,
internal cavities, hot cracking dilution, etc., which make it an alternative for most
beam-based MAM methods. Srivastava et al. (2021) point out that FSAM is a rapidly
growing technique, executed by joining various materials layer upon layer to develop
a 3D object from digital data, working on the principle of friction stir welding. The
main difference is that joining of a layer by another layer which is associated with
reheating and re-sintering of a material and flexibility to adjust the reheating and
re-sintering time allow the process to control the microstructural features, so that
desired mechanical properties can be obtained.
As emphasized by Węglowski (2018), other areas of possible FSP applications
include increasing materials plasticity, modification of welded joints, production of
Remanufacturing and Advanced Machining
size of this zone varies from several micrometers to millimeters dependent
on the material and transition from the SZ to the TMAZ is usually not
sharp. Soft metals, e.g., aluminum and magnesium, have wider zones compared to harder materials such as steel and titanium.
3. Heat-affected zone (HAZ) is placed between TMAZ and base material.
This zone experiences no strain and is subjected to only thermal cycles
which can lead to some grain growth. Mechanical properties in HAZ are
poor, causing failures during tensile tests.
The zones exist on both the advancing and the retreating side; however, they may
not have the same width on either side. The size of each zone depends on a number
of process parameters.
Single-pass FSP comprises a tool that travels in a selected area only once, but if
the tool is traversed again in the same or reverse direction on a previously processed
area, wholly or partially, then it is referred to as “multi-pass FSP.” Harwani et al.
(2021) underline that multi-pass FSP can furnish grain size reduction and texture
weakening more than single-pass processing due to cumulative strain rates in the
successive passes and also enhances the homogeneous distribution of grains in the
material. In fact, FSP performs selective superplastic forming in desired regions.
Gangil et al. (2021) describe FSP as a technique for strengthening of high specific
strength alloys, including age-hardened aluminum alloys, for several industrial
applications through surface composite fabrication, where friction stir processing
generates reinforcement particles.
Węglowski (2018) points out that FSP, like other FSW techniques, can be carried
out using both specialized and typical milling machines. The former are equipped
with dedicated measurement systems, whereas the latter need a universal measurement head. However, milling machines generally fail to provide ideal conditions for
FSP due to an important issue of independent measurement systems development.
The ability of FSP and FSW to provide improved microstructural and mechanical
properties by the grain refining process has given rise to an alternative method of
solid-state (non-melting) process named friction stir-based additive manufacturing
(FSAM) (Srivastava et al., 2021). The process has many benefits, such as solid-state
nature, wrought microstructural properties, flexibility in material feed, and capability to process almost any type of metals and alloys. Due to low temperatures, FSAM
can produce components with negligible porosity, inclusions, particle segregation,
internal cavities, hot cracking dilution, etc., which make it an alternative for most
beam-based MAM methods. Srivastava et al. (2021) point out that FSAM is a rapidly
growing technique, executed by joining various materials layer upon layer to develop
a 3D object from digital data, working on the principle of friction stir welding. The
main difference is that joining of a layer by another layer which is associated with
reheating and re-sintering of a material and flexibility to adjust the reheating and
re-sintering time allow the process to control the microstructural features, so that
desired mechanical properties can be obtained.
As emphasized by Węglowski (2018), other areas of possible FSP applications
include increasing materials plasticity, modification of welded joints, production of