24
D. Shah and V. J. Badheka
of this technology have a competitive edge over the conventional additive manufacturing (AM) techniques. This technology provides major advantages at two fronts:
(a) increases production efficiency and (b) increases part efficiency.
FSAM processes can answer the problem of energy reduction and thus decrease
the production cost and more importantly have a positive impact on the environment
[84]. A method is designed to calculate the mean energy consumption of fusion
additive processes. The mean power required was 2–3 kW for fabricating a building
according to this methodology. For the EOSINST laser-based process, the specific
energy efficiency was reported between 100 and 400 MJ/kg [84]. The energy required
for a friction-based process for an analogous operation was approximately 2.5% of
that of the fusion-based counterpart operation [74]. This drastic difference has given
much impetus to the development of FSAMs. Further, Boeing published a report
in 2012 [36] that estimated an emission reduction of 60 billion pounds of CO 2
and volume reduction of nearly 5 billion pounds of Al over the next 25 years using
friction-based technologies. This report concluded that a shift towards friction-based
technologies from conventional techniques will be a metamorphosis in the field of
sustainable manufacturing space [85].
The increased part efficiency of FSAM products as compared to the fusion alternatives is due to the solid-state nature of the process. A typical laser and electron
beam AM involve a much larger heat flux of ~107 W/m
2 as compared to ~103 W/m
2
heat flux involved in FSAM techniques [86]. Intense thermal gradients develop in the
fusion-based methods because of the high heat flux which makes the welds susceptible to cast structure defects, residual stress, rapid solidification defects like cavities,
porosities, thermal cracking and result in lower mechanical strength and lower weld
quality. Moreover, post-weld treatments are necessary to increase the strengths of the
welds. All these shortcomings are eliminated due to the intrinsic property of solidstate welding, and a part with higher structural integrity and wrought microstructure
can be obtained with FSAM.
4.2 Material Feasibility of Friction Stir Additive
Manufacturing
The void spaces of metal additive manufacturing that are inaccessible with fusionbased technologies can be filled with friction-based additive manufacturing technologies. These technologies can be employed for welding of similar as well as dissimilar
alloys. Structures of ferrous and non-ferrous alloys, pure metals and composites can
be fabricated with this technique. Areas of additive manufacturing that are hard to
access due to the fusion-based hindrances can be tackled with these technologies.
One such area is where FSAM can contribute to additive manufacturing of metals
is the manufacturing of high-strength Al alloys which are not viable using fusionbased techniques due to hot cracking [85]. Al alloys 2XXX and 7XXX which have
high strength (>400 MPa) bolster the potential of FSAM because of their requirement
D. Shah and V. J. Badheka
of this technology have a competitive edge over the conventional additive manufacturing (AM) techniques. This technology provides major advantages at two fronts:
(a) increases production efficiency and (b) increases part efficiency.
FSAM processes can answer the problem of energy reduction and thus decrease
the production cost and more importantly have a positive impact on the environment
[84]. A method is designed to calculate the mean energy consumption of fusion
additive processes. The mean power required was 2–3 kW for fabricating a building
according to this methodology. For the EOSINST laser-based process, the specific
energy efficiency was reported between 100 and 400 MJ/kg [84]. The energy required
for a friction-based process for an analogous operation was approximately 2.5% of
that of the fusion-based counterpart operation [74]. This drastic difference has given
much impetus to the development of FSAMs. Further, Boeing published a report
in 2012 [36] that estimated an emission reduction of 60 billion pounds of CO 2
and volume reduction of nearly 5 billion pounds of Al over the next 25 years using
friction-based technologies. This report concluded that a shift towards friction-based
technologies from conventional techniques will be a metamorphosis in the field of
sustainable manufacturing space [85].
The increased part efficiency of FSAM products as compared to the fusion alternatives is due to the solid-state nature of the process. A typical laser and electron
beam AM involve a much larger heat flux of ~107 W/m
2 as compared to ~103 W/m
2
heat flux involved in FSAM techniques [86]. Intense thermal gradients develop in the
fusion-based methods because of the high heat flux which makes the welds susceptible to cast structure defects, residual stress, rapid solidification defects like cavities,
porosities, thermal cracking and result in lower mechanical strength and lower weld
quality. Moreover, post-weld treatments are necessary to increase the strengths of the
welds. All these shortcomings are eliminated due to the intrinsic property of solidstate welding, and a part with higher structural integrity and wrought microstructure
can be obtained with FSAM.
4.2 Material Feasibility of Friction Stir Additive
Manufacturing
The void spaces of metal additive manufacturing that are inaccessible with fusionbased technologies can be filled with friction-based additive manufacturing technologies. These technologies can be employed for welding of similar as well as dissimilar
alloys. Structures of ferrous and non-ferrous alloys, pure metals and composites can
be fabricated with this technique. Areas of additive manufacturing that are hard to
access due to the fusion-based hindrances can be tackled with these technologies.
One such area is where FSAM can contribute to additive manufacturing of metals
is the manufacturing of high-strength Al alloys which are not viable using fusionbased techniques due to hot cracking [85]. Al alloys 2XXX and 7XXX which have
high strength (>400 MPa) bolster the potential of FSAM because of their requirement