Abstract
Superplastic deformation of engineering materials is often represented by high elongation values obtained in conventional tensile tests carried out in specific ranges of temperatures and strain rates. This behavior is characterized by high strain rate sensitivity (SRS) indices obtained by a variety of techniques. The SRS of a fine-grained Sn–1 wt% Bi alloy, processed by multi-directional forging (MDF) was studied by indentation testing at room temperature (T > 0.6Tm). The microstructural homogeneity increased with increasing the number of MDF passes, and the grain size decreased from 3.2 to 2 μm, as the number of passes increased from 1 to 8. The SRS indices of 0.08, 0.24, 0.31, and 0.49 were obtained for the 2, 4, 6 and 8 passes of MDF, respectively. The high SRS index of 0.49, calculated from different analysis methods of the indentation tests are in good agreement with each other and with those of the other testing methods and severe plastic deformation processes on the same alloy reported in the literature. These SRS indices together with the uniform fine-grained equiaxed microstructure with an average grain size of 2 μm, observed after 8 MDF passes, are indicative of a superplastic deformation behavior dominated by grain boundary sliding..
Highlights
Severe plastic deformation (SPD) processes have received great attention for their capability in producing very fine grain sizes
The Optical micrographs of the material before the multi-directional forging (MDF) process and after 8 passes of MDF are shown in Figs. 2 and 3, respectively
The microstructure of the material after 8 passes of MDF, depicted in Fig 3a, is indicative of a more refined state, implying that dynamic recrystallization has occurred during the MDF process
Summary
Severe plastic deformation (SPD) processes have received great attention for their capability in producing very fine grain sizes. Different processes have been developed and their potentials and limitations have been documented. Multi-directional forging (MDF) has proved to be a possible means for attaining fine grain structures suitable for superplastic deformation of aluminum [1], magnesium [2], and titanium alloys [3]. MDF is a repeating compression process in which the axis of the applied strain changes in each step [4]. Considerable plastic strain is accumulated in the material as it is repeatedly deformed at ambient to elevated temperatures. It has been shown that the evolution of equiaxed fine grains relies mainly on the strain accumulation applied from various directions [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
