CHANDRA S PERUGU | Indian Institute of Science (original) (raw)

Papers by CHANDRA S PERUGU

TMS 2018 147th Annual Meeting & Exhibition Supplemental Proceedings, 2018

Traditional alloys are designed on the basis of one or more majority of materials which is Fe-bas... more Traditional alloys are designed on the basis of one or more majority of materials which is Fe-based, Ni-based, and Co-based super alloy for mechanical properties enhancement but results with poor ductility at room temperature. New alloy design of materials requires more alloying elements for improving the material properties consistently. High entropy alloy consists of at least five principal elements with the concentration of each material between 5 and 35 at.% on the basis of maximum configurational entropy at equi-atomic composition with more stable than intermetallic at elevated temperatures. In this paper, FeCrNbVMn alloy phase formed by mechanical alloying. The mechanically alloyed powders were subsequently consolidated by cold pressing and sintered in tube furnace. Analysis of microstructure and mechanical properties were carried out with the help of XRD, SEM, TEM and nanoindetation tests. The bulk sample showed hardness of ~19 GPa at nano scale.

Materials Science and Engineering: A, 2019

Friction stir processing (FSP) was applied to graphene nanoplatelets (GNPs) physically compacted ... more Friction stir processing (FSP) was applied to graphene nanoplatelets (GNPs) physically compacted on the surface of squeeze cast A356 alloy to incorporate GNPs within the matrix and to improve its mechanical properties. Squeeze casting resulted in finer size silicon and intermetallic compounds in cast microstructure, and subsequently FSP further refined the microstructure of squeeze cast A356 alloy, and GNP reinforced A356 alloy. The finer Si particles, intermetallics and graphene dispersed in the matrix increased the yield and ultimate tensile strength of FSP squeeze cast A356 alloy compared to the results reported in prior literature for FSP A356 alloy. Eutectic Si needles have been converted to fine spherical particles during FSP and were uniformly distributed within the nugget zone. The crystallite size of GNPs which were physically adhered to the surface of squeeze cast alloy prior to FSP decreased after FSP as a result of deformation. Thus, a combination of squeeze casting, and friction stir processing and incorporation of GNPs reinforcement in the A356 matrix is a promising route to further improve its mechanical properties.

Materials Science and Engineering: A, 2018

The influence of hot rolling on the microstructure and subsequent mechanical characteristics of e... more The influence of hot rolling on the microstructure and subsequent mechanical characteristics of explosive-welded ferritic stainless steel (FSS)/carbon steel (CS) laminate was investigated. The results indicate that by hot rolling, decarburization layer disappears and a uniform structure is gained in CS side, but ferrite grains and carbides in constituent FSS form an uneven band microstructure which is denser at superficial zone than near the interface. The transmission electron microscopy results indicate that the layers adhering to the interface show typical deformed microstructure features, i.e., stream-like strips and elongated grains in FSS plates, carbide precipitates and bended cementite fragments in CS plates; and high-density dislocations in both plates. With hot rolling, various mechanical strengths and hardness are increased, while the elongation percentage is diminished. Examination of fractographs from tensile tests reveals predominately small dimples for explosive-welded specimens, whereas both big dimples and cleavage fracture for rolled specimens. Stereomicroscopic fractographs taken on shear samples indicate that the surfaces of explosive-welded specimens exhibit uniform deformation, but uneven deformation is displayed for that of rolled specimens. These results indicate that hot rolling is beneficial to improve the strength of explosive-welded FSS/CS laminate but not good for enhancing its plasticity.

Journal of Alloys and Compounds, 2019

Welding of shape memory alloys without deterioration of shape memory effect could vastly extend t... more Welding of shape memory alloys without deterioration of shape memory effect could vastly extend their applications. To retain shape memory behavior, a solid-state welding technique called friction stir welding was employed in this study. Austenitic NiTi alloy sheets of thickness 1.2 mm were joined at tool rotational speeds of 800, 1000, and 1200 rpm. Due to dynamic recrystallization, the grain refinement has occurred in the weld region. The tensile testing has shown superelastic plateau for the welds at 800 and 1000 rpm. The phase transformation behavior of different weld regions was studied in detail using differential scanning calorimeter. A marginal drift in transformation temperatures was observed in the weld. To understand the drift in phase transformation temperatures, finite element analysis was carried out with focus on temperature distribution during welding. Finally, time-dependent shape recovery of a FSW welded joint was studied and it was found that the original position was completely recovered after 27 s at a temperature of 65 C.

Metallurgical and Materials Transactions A, 2017

The effect of individual and mixed additions of calcium (Ca) and antimony (Sb) on the corrosion b... more The effect of individual and mixed additions of calcium (Ca) and antimony (Sb) on the corrosion behavior of the squeeze-cast AZ91 alloy have been investigated. The corrosion resistance of all modified alloys is better as a result of the refined and reduced volume fraction of the b-Mg 17 Al 12 phase as well as grain refinement. Individual additions are better than mixed additions. The AZ91-1.0Ca (AZX911) alloy comprising individual Ca addition with a continuous network of the Al 2 Ca phase reveals the lowest corrosion rate. Among the alloys comprising combined additions, the AZ91-2.0Ca-0.3Sb (AZXY9120) alloy exhibits the best corrosion resistance because of the higher and lower volume fractions of the Al 2 Ca and Ca 2 Sb phases, respectively.

Journal of Materials Engineering and Performance, 2018

Aluminum-based composites have many advantages over their conventional counterparts. A major prob... more Aluminum-based composites have many advantages over their conventional counterparts. A major problem in such composites is the clustering of particles in the matrix. Friction stir processing (FSP) can homogenize particle distribution in aluminum-based composites. In this study, unannealed TiO2 particles were used to prepare Al-TiO2 nanocomposite using FSP. The TiO2 particles, about 1 µm, were dispersed into an aluminum matrix by 6 passes of FSP. The TiO2 particles were fractured by multiple FSP passes, leading to a nano-size particle distribution in the matrix. Nanoscale dispersion was confirmed by scanning electron microscopy and transmission electron microscopy. The fractured TiO2 particles reacted with the aluminum matrix to form Al3Ti intermetallic and Al2O3 ceramic. The progression of the Al-TiO2 reaction from the fourth to the sixth pass of FSP was revealed by x-ray diffraction. Due to the nanoscale dispersion, the yield and ultimate tensile strength of the composite increased to 97 and 145 MPa, respectively. Ductility of the composite decreased marginally compared to the as-received aluminum. As the dispersed particles pin dislocations, the strain-hardening rate of the composite was considerably increased and the same was seen in the Kocks-Mecking plot. The TiO2 particles are mechanically activated due to their fracture during FSP, hence leading to reaction with the matrix. The particle refinement and dispersion lead to a homogeneous matrix with higher strength.

Intermetallics, 2016

For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW... more For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW). The weld showed significant grain refinement without formation of detrimental phases. The yield strength of the weld joint increased by 17% as compared to the base metal without substantial change in shape memory behaviour.

Advances in Materials and Processing Technologies, 2020

Aluminium matrix composites processed through in-situ molten reaction has emerged as an alternati... more Aluminium matrix composites processed through in-situ molten reaction has emerged as an alternative for eliminating defects existing in ex-situ reinforced metal matrix composites. Development of composites through in-situ method using inorganic salts via liquid metallurgy route is the most widely accepted technique. In the present work, Al6061-ZrB2 in-situ composites have been developed through in-situ reaction of Al-10%Zr and Al-3%B master alloys in Al6061 alloy. Study of microstructure and mechanical properties of in-situ reinforced ZrB2 in Al6061 alloy have been carried out. Composite exhibited grain refinement and improved the mechanical properties of Al6061 alloy. Ductility of composite is reduced with increase in content of ZrB2.

Journal of Alloys and Compounds, 2021

Metal/alloy matrices have been previously reinforced with ceramic nanoparticles, but such reinfor... more Metal/alloy matrices have been previously reinforced with ceramic nanoparticles, but such reinforcements tend to agglomerate, have weak interfaces, and are expensive. Polymer-derived ceramics (PDCs) based composites can potentially overcome these shortcomings. These composites are obtained from the preceramic polymers after pyrolysis. These polymers are inexpensive, can be fragmented to the nanoscale, and pyrolyzed in-situ. Friction stir processing (FSP) was used to fragment and disperse the polymer within an Al-Mg alloy. The PDC particles pinned the dislocations and grain boundaries. The composite exhibited a microstructure resulting from dynamic recrystallization with an average grain size of ~1 µm. It also exhibited both high strength (96% and 24% improvement in the yield and tensile strength, respectively) and good ductility. Interestingly, the serrations in the tensile curves commonly observed in Al-Mg alloys due to the Portevin-Le Chatelier (PLC) effect was reduced in the comp...

Traditional alloys are designed on the basis of one or more majority of materials which is Fe-bas... more Traditional alloys are designed on the basis of one or more majority of materials which is Fe-based, Ni-based, and Co-based super alloy for mechanical properties enhancement but results with poor ductility at room temperature. New alloy design of materials requires more alloying elements for improving the material properties consistently. High entropy alloy consists of at least five principal elements with the concentration of each material between 5 and 35 at.% on the basis of maximum configurational entropy at equi-atomic composition with more stable than intermetallic at elevated temperatures. In this paper, FeCrNbVMn alloy phase formed by mechanical alloying. The mechanically alloyed powders were subsequently consolidated by cold pressing and sintered in tube furnace. Analysis of microstructure and mechanical properties were carried out with the help of XRD, SEM, TEM and nanoindetation tests. The bulk sample showed hardness of ∼19 GPa at nano scale.

JOM, 2021

A challenge for the research and industrial community is to develop lightweight wrought Mg-based ... more A challenge for the research and industrial community is to develop lightweight wrought Mg-based alloys that exhibit high strength and good ductility. To address this challenge, Mg-3Sn-2Al (TA32) alloy was produced by the squeeze casting process followed by hot rolling (HR). To improve its ductility, the hot-rolled alloy was annealed (HRA). HR and HRA samples were subjected to microstructural, composition, textural, and mechanical property analysis. The HR sheet exhibited high strength with 0.2% proof stress (PS) of 274 MPa and ultimate tensile strength (UTS) of 390 MPa, as well as reasonable ductility (12%) along the rolling direction, one of the highest values for Mg alloys. HRA sheet showed a moderate reduction in strength with a 0.2% PS of 250 MPa and UTS of 365 MPa, but an improvement in ductility (19%). The excellent properties of this alloy can be attributed to the synergistic effects of grain refinement, solid-solution strengthening by Al and Sn atoms, and uniform distributi...

Surface and Coatings Technology

Journal of Manufacturing Processes

Materials Characterization

Metallurgical and Materials Transactions A

Materials Today Communications

TMS 2018 147th Annual Meeting & Exhibition Supplemental Proceedings, 2018

Traditional alloys are designed on the basis of one or more majority of materials which is Fe-bas... more Traditional alloys are designed on the basis of one or more majority of materials which is Fe-based, Ni-based, and Co-based super alloy for mechanical properties enhancement but results with poor ductility at room temperature. New alloy design of materials requires more alloying elements for improving the material properties consistently. High entropy alloy consists of at least five principal elements with the concentration of each material between 5 and 35 at.% on the basis of maximum configurational entropy at equi-atomic composition with more stable than intermetallic at elevated temperatures. In this paper, FeCrNbVMn alloy phase formed by mechanical alloying. The mechanically alloyed powders were subsequently consolidated by cold pressing and sintered in tube furnace. Analysis of microstructure and mechanical properties were carried out with the help of XRD, SEM, TEM and nanoindetation tests. The bulk sample showed hardness of ~19 GPa at nano scale.

Materials Science and Engineering: A, 2019

Friction stir processing (FSP) was applied to graphene nanoplatelets (GNPs) physically compacted ... more Friction stir processing (FSP) was applied to graphene nanoplatelets (GNPs) physically compacted on the surface of squeeze cast A356 alloy to incorporate GNPs within the matrix and to improve its mechanical properties. Squeeze casting resulted in finer size silicon and intermetallic compounds in cast microstructure, and subsequently FSP further refined the microstructure of squeeze cast A356 alloy, and GNP reinforced A356 alloy. The finer Si particles, intermetallics and graphene dispersed in the matrix increased the yield and ultimate tensile strength of FSP squeeze cast A356 alloy compared to the results reported in prior literature for FSP A356 alloy. Eutectic Si needles have been converted to fine spherical particles during FSP and were uniformly distributed within the nugget zone. The crystallite size of GNPs which were physically adhered to the surface of squeeze cast alloy prior to FSP decreased after FSP as a result of deformation. Thus, a combination of squeeze casting, and friction stir processing and incorporation of GNPs reinforcement in the A356 matrix is a promising route to further improve its mechanical properties.

Materials Science and Engineering: A, 2018

The influence of hot rolling on the microstructure and subsequent mechanical characteristics of e... more The influence of hot rolling on the microstructure and subsequent mechanical characteristics of explosive-welded ferritic stainless steel (FSS)/carbon steel (CS) laminate was investigated. The results indicate that by hot rolling, decarburization layer disappears and a uniform structure is gained in CS side, but ferrite grains and carbides in constituent FSS form an uneven band microstructure which is denser at superficial zone than near the interface. The transmission electron microscopy results indicate that the layers adhering to the interface show typical deformed microstructure features, i.e., stream-like strips and elongated grains in FSS plates, carbide precipitates and bended cementite fragments in CS plates; and high-density dislocations in both plates. With hot rolling, various mechanical strengths and hardness are increased, while the elongation percentage is diminished. Examination of fractographs from tensile tests reveals predominately small dimples for explosive-welded specimens, whereas both big dimples and cleavage fracture for rolled specimens. Stereomicroscopic fractographs taken on shear samples indicate that the surfaces of explosive-welded specimens exhibit uniform deformation, but uneven deformation is displayed for that of rolled specimens. These results indicate that hot rolling is beneficial to improve the strength of explosive-welded FSS/CS laminate but not good for enhancing its plasticity.

Journal of Alloys and Compounds, 2019

Welding of shape memory alloys without deterioration of shape memory effect could vastly extend t... more Welding of shape memory alloys without deterioration of shape memory effect could vastly extend their applications. To retain shape memory behavior, a solid-state welding technique called friction stir welding was employed in this study. Austenitic NiTi alloy sheets of thickness 1.2 mm were joined at tool rotational speeds of 800, 1000, and 1200 rpm. Due to dynamic recrystallization, the grain refinement has occurred in the weld region. The tensile testing has shown superelastic plateau for the welds at 800 and 1000 rpm. The phase transformation behavior of different weld regions was studied in detail using differential scanning calorimeter. A marginal drift in transformation temperatures was observed in the weld. To understand the drift in phase transformation temperatures, finite element analysis was carried out with focus on temperature distribution during welding. Finally, time-dependent shape recovery of a FSW welded joint was studied and it was found that the original position was completely recovered after 27 s at a temperature of 65 C.

Metallurgical and Materials Transactions A, 2017

The effect of individual and mixed additions of calcium (Ca) and antimony (Sb) on the corrosion b... more The effect of individual and mixed additions of calcium (Ca) and antimony (Sb) on the corrosion behavior of the squeeze-cast AZ91 alloy have been investigated. The corrosion resistance of all modified alloys is better as a result of the refined and reduced volume fraction of the b-Mg 17 Al 12 phase as well as grain refinement. Individual additions are better than mixed additions. The AZ91-1.0Ca (AZX911) alloy comprising individual Ca addition with a continuous network of the Al 2 Ca phase reveals the lowest corrosion rate. Among the alloys comprising combined additions, the AZ91-2.0Ca-0.3Sb (AZXY9120) alloy exhibits the best corrosion resistance because of the higher and lower volume fractions of the Al 2 Ca and Ca 2 Sb phases, respectively.

Journal of Materials Engineering and Performance, 2018

Aluminum-based composites have many advantages over their conventional counterparts. A major prob... more Aluminum-based composites have many advantages over their conventional counterparts. A major problem in such composites is the clustering of particles in the matrix. Friction stir processing (FSP) can homogenize particle distribution in aluminum-based composites. In this study, unannealed TiO2 particles were used to prepare Al-TiO2 nanocomposite using FSP. The TiO2 particles, about 1 µm, were dispersed into an aluminum matrix by 6 passes of FSP. The TiO2 particles were fractured by multiple FSP passes, leading to a nano-size particle distribution in the matrix. Nanoscale dispersion was confirmed by scanning electron microscopy and transmission electron microscopy. The fractured TiO2 particles reacted with the aluminum matrix to form Al3Ti intermetallic and Al2O3 ceramic. The progression of the Al-TiO2 reaction from the fourth to the sixth pass of FSP was revealed by x-ray diffraction. Due to the nanoscale dispersion, the yield and ultimate tensile strength of the composite increased to 97 and 145 MPa, respectively. Ductility of the composite decreased marginally compared to the as-received aluminum. As the dispersed particles pin dislocations, the strain-hardening rate of the composite was considerably increased and the same was seen in the Kocks-Mecking plot. The TiO2 particles are mechanically activated due to their fracture during FSP, hence leading to reaction with the matrix. The particle refinement and dispersion lead to a homogeneous matrix with higher strength.

Intermetallics, 2016

For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW... more For the first time, NiTi shape memory alloy was successfully joined by Friction Stir Welding (FSW). The weld showed significant grain refinement without formation of detrimental phases. The yield strength of the weld joint increased by 17% as compared to the base metal without substantial change in shape memory behaviour.

Advances in Materials and Processing Technologies, 2020

Aluminium matrix composites processed through in-situ molten reaction has emerged as an alternati... more Aluminium matrix composites processed through in-situ molten reaction has emerged as an alternative for eliminating defects existing in ex-situ reinforced metal matrix composites. Development of composites through in-situ method using inorganic salts via liquid metallurgy route is the most widely accepted technique. In the present work, Al6061-ZrB2 in-situ composites have been developed through in-situ reaction of Al-10%Zr and Al-3%B master alloys in Al6061 alloy. Study of microstructure and mechanical properties of in-situ reinforced ZrB2 in Al6061 alloy have been carried out. Composite exhibited grain refinement and improved the mechanical properties of Al6061 alloy. Ductility of composite is reduced with increase in content of ZrB2.

Journal of Alloys and Compounds, 2021

Metal/alloy matrices have been previously reinforced with ceramic nanoparticles, but such reinfor... more Metal/alloy matrices have been previously reinforced with ceramic nanoparticles, but such reinforcements tend to agglomerate, have weak interfaces, and are expensive. Polymer-derived ceramics (PDCs) based composites can potentially overcome these shortcomings. These composites are obtained from the preceramic polymers after pyrolysis. These polymers are inexpensive, can be fragmented to the nanoscale, and pyrolyzed in-situ. Friction stir processing (FSP) was used to fragment and disperse the polymer within an Al-Mg alloy. The PDC particles pinned the dislocations and grain boundaries. The composite exhibited a microstructure resulting from dynamic recrystallization with an average grain size of ~1 µm. It also exhibited both high strength (96% and 24% improvement in the yield and tensile strength, respectively) and good ductility. Interestingly, the serrations in the tensile curves commonly observed in Al-Mg alloys due to the Portevin-Le Chatelier (PLC) effect was reduced in the comp...

Traditional alloys are designed on the basis of one or more majority of materials which is Fe-bas... more Traditional alloys are designed on the basis of one or more majority of materials which is Fe-based, Ni-based, and Co-based super alloy for mechanical properties enhancement but results with poor ductility at room temperature. New alloy design of materials requires more alloying elements for improving the material properties consistently. High entropy alloy consists of at least five principal elements with the concentration of each material between 5 and 35 at.% on the basis of maximum configurational entropy at equi-atomic composition with more stable than intermetallic at elevated temperatures. In this paper, FeCrNbVMn alloy phase formed by mechanical alloying. The mechanically alloyed powders were subsequently consolidated by cold pressing and sintered in tube furnace. Analysis of microstructure and mechanical properties were carried out with the help of XRD, SEM, TEM and nanoindetation tests. The bulk sample showed hardness of ∼19 GPa at nano scale.

JOM, 2021

A challenge for the research and industrial community is to develop lightweight wrought Mg-based ... more A challenge for the research and industrial community is to develop lightweight wrought Mg-based alloys that exhibit high strength and good ductility. To address this challenge, Mg-3Sn-2Al (TA32) alloy was produced by the squeeze casting process followed by hot rolling (HR). To improve its ductility, the hot-rolled alloy was annealed (HRA). HR and HRA samples were subjected to microstructural, composition, textural, and mechanical property analysis. The HR sheet exhibited high strength with 0.2% proof stress (PS) of 274 MPa and ultimate tensile strength (UTS) of 390 MPa, as well as reasonable ductility (12%) along the rolling direction, one of the highest values for Mg alloys. HRA sheet showed a moderate reduction in strength with a 0.2% PS of 250 MPa and UTS of 365 MPa, but an improvement in ductility (19%). The excellent properties of this alloy can be attributed to the synergistic effects of grain refinement, solid-solution strengthening by Al and Sn atoms, and uniform distributi...

Surface and Coatings Technology

Journal of Manufacturing Processes

Materials Characterization

Metallurgical and Materials Transactions A

Materials Today Communications