394
D. M. Harwani et al.
4 Challenges and Future Scope
Almost all the above discussed SPD routes are confined to the laboratory experiments and research only. At present, superplastic parts that are complex in design
and having low volume of production have been used only in the niche areas like
aerospace sector. Automotive field, which strictly depends on high productivity, is
yet to commercially implement SPF. Owing to the reason of more time consumption, as these methods require more number of passes to reduce the grain size to the
desirable level.
To make SPF economical from the industrial viewpoint, high strain rate superplasticity (HSRS) is very appealing. Elongations more than 200% achieved at strain rates
above 10
−2 /s is coined as HSRS [51]. It will help in increasing the strain rates in less
cycle time and thus increasing the productivity. Fine grain size and high deformation
temperatures are the major requirements for achieving HSRS [52]. But the industrial
sector emphasizes on lower forming temperatures which result in lower material and
tooling costs. Hence, it poses a unique challenge to optimize the forming parameters
(temperature and strain rate) as well as the processing parameters to obtain superplasticity at higher strain rates and optimum temperatures in order to make SPF more
popular in automotive industries.
Another challenge is the tendency of formation of inter-granular cavities during
hot superplastic deformation [53]. Such cavitations deteriorate the overall properties
of the finished part which is undesirable. The temperature and strain rates for superplastic deformation should be optimized in such a way so as to reduce this cavitation
tendency.
Limited amount of work has been done in the area of superplasticity of nonferrous metals like Cu, Ni and Mg. Composite materials and Zn–Al eutectoids have
also caught the attention of the researchers for developing superplasticity. This can
become the research prospect for further investigations. Also, more efforts can be
directed for simulation and modeling of superplasticity phenomenon so that it can
be commercially implemented with the use of techniques like FEM [54].
A very recent study has utilized a combination of ECAE followed by rolling
process and achieved 667% elongations with ultra-fine grains in the matrix of AA
5083 sheet [19]. This has clearly opened up new horizons to achieve faster grain
size reduction and enhanced superplastic behavior with the blend of dissimilar SPD
processes.
References
1. Koehler W, Plege B, Sahm KF, Padmapriya N (2016) Metal forming: specialized procedures
for the aircraft industry. Ref Module Mater Sci Mater Eng. https://doi.org/10.1016/B978-0-12803581-8.011939-1
2. Mukherjee AK (2006) Superplasticity in metals, ceramics and intermetallics. Mater Sci
Technol. https://doi.org/10.1002/9783527603978
D. M. Harwani et al.
4 Challenges and Future Scope
Almost all the above discussed SPD routes are confined to the laboratory experiments and research only. At present, superplastic parts that are complex in design
and having low volume of production have been used only in the niche areas like
aerospace sector. Automotive field, which strictly depends on high productivity, is
yet to commercially implement SPF. Owing to the reason of more time consumption, as these methods require more number of passes to reduce the grain size to the
desirable level.
To make SPF economical from the industrial viewpoint, high strain rate superplasticity (HSRS) is very appealing. Elongations more than 200% achieved at strain rates
above 10
−2 /s is coined as HSRS [51]. It will help in increasing the strain rates in less
cycle time and thus increasing the productivity. Fine grain size and high deformation
temperatures are the major requirements for achieving HSRS [52]. But the industrial
sector emphasizes on lower forming temperatures which result in lower material and
tooling costs. Hence, it poses a unique challenge to optimize the forming parameters
(temperature and strain rate) as well as the processing parameters to obtain superplasticity at higher strain rates and optimum temperatures in order to make SPF more
popular in automotive industries.
Another challenge is the tendency of formation of inter-granular cavities during
hot superplastic deformation [53]. Such cavitations deteriorate the overall properties
of the finished part which is undesirable. The temperature and strain rates for superplastic deformation should be optimized in such a way so as to reduce this cavitation
tendency.
Limited amount of work has been done in the area of superplasticity of nonferrous metals like Cu, Ni and Mg. Composite materials and Zn–Al eutectoids have
also caught the attention of the researchers for developing superplasticity. This can
become the research prospect for further investigations. Also, more efforts can be
directed for simulation and modeling of superplasticity phenomenon so that it can
be commercially implemented with the use of techniques like FEM [54].
A very recent study has utilized a combination of ECAE followed by rolling
process and achieved 667% elongations with ultra-fine grains in the matrix of AA
5083 sheet [19]. This has clearly opened up new horizons to achieve faster grain
size reduction and enhanced superplastic behavior with the blend of dissimilar SPD
processes.
References
1. Koehler W, Plege B, Sahm KF, Padmapriya N (2016) Metal forming: specialized procedures
for the aircraft industry. Ref Module Mater Sci Mater Eng. https://doi.org/10.1016/B978-0-12803581-8.011939-1
2. Mukherjee AK (2006) Superplasticity in metals, ceramics and intermetallics. Mater Sci
Technol. https://doi.org/10.1002/9783527603978