Olatunji Oladimeji Ojo - Academia.edu (original) (raw)

Uploads

Papers by Olatunji Oladimeji Ojo

Research paper thumbnail of Friction spot extrusion welding-brazing of copper to aluminum alloy

Materials Letters, Feb 1, 2021

Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn... more Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn as interlayer has been elucidated. The effect of shoulder geometry on the microstructural characterizations and mechanical behavior of the joints was explored. Results indicated that changing the geometry of the shoulder from cylindrical to triangular not only enlarged the brazed zone from 14.98 lm to 19.65 lm, but also the tensile/shear strength had a rising trend and improved from 3268 N to 4398 N, which can be attributed to the larger brazed zone and complete filling of the pre-threaded hole in the joint produced by the triangular shoulder.

Research paper thumbnail of Friction stir processing of hybridized AZ31B magnesium alloy-based composites by adding CeO2 and ZrO2powders: mechanical, wear, and corrosion behaviors

Journal of materials research and technology, May 1, 2023

Research paper thumbnail of Probe-less friction stir spot processing (PFSSP) of AA5754/AA5083 joint by adding the B4C ceramics: Effect of shoulder features on mechanical properties and tribological behavior

Research paper thumbnail of Impact of multiple FSP passes on structure, mechanical, tribological and corrosion behaviors of AA6061/316 stainless-steel reinforced Al matrix composites

Surface & Coatings Technology, Oct 1, 2022

Research paper thumbnail of Weldability and mechanical properties of AA5083-H112 aluminum alloy and pure copper dissimilar friction spot extrusion welding-brazing

Vacuum, May 1, 2021

Abstract The friction spot extrusion welding-brazing (FSEW-B) process was employed to join AA5083... more Abstract The friction spot extrusion welding-brazing (FSEW-B) process was employed to join AA5083-H112 aluminum alloy and pure Cu via the use of a Zn interlayer to improve the mechanical properties of the dissimilar joint. The attained data indicated that not only FSEW-B led to the elimination of the keyhole, which is an intrinsic flaw of the Friction Stir Spot Welding (FSSW) process, but also the results showed that adding Zn interlayer was propitious to make less brittle intermetallic compounds (IMCs) like Al4Cu9 at the Cu/Al interface. More importantly, tensile shear results demonstrated an improvement in the strength and ductility of the FSEW-B weld sample (reached 156.2 MPa), which is attributable to the lack of keyhole defect and brittle IMCs in the joint.

Research paper thumbnail of Diffusion brazing of 321 stainless steel to IN738 using 54Ag-40Cu-5.0Zn-1.0Ni powder-mixture interlayer

Materials Letters, Aug 1, 2021

Research paper thumbnail of Influence of shoulder diameter on interfacial microstructure and mechanical behavior in dieless friction stir riveting of CP-Copper to 321 stainless steel

Research paper thumbnail of Friction spot extrusion brazing of copper to AISI 304 stainless steel with Zn interlayer: effect of shoulder surface modification

Archives of Civil and Mechanical Engineering, Feb 7, 2022

Research paper thumbnail of Effect of shoulder features during friction spot extrusion welding of 2024-T3 to 6061-T6 aluminium alloys

Archives of Civil and Mechanical Engineering, Jul 4, 2020

Friction spot extrusion welding process is successfully performed on dissimilar aluminum alloys o... more Friction spot extrusion welding process is successfully performed on dissimilar aluminum alloys of AA2024-T3 and AA6061-T6 under the influence of shoulder features. The joints were analysed by microstructural features and mechanical properties using conventional and advanced tools of visual inspection, optical microscopy, scanning electron microscopy, transmission electron microscopy, electron back scattered diffractions, tensile testing and hardness testing. The results revealed that the joining was obtained by combination of mechanical locking from extruded material of top surface to predrilled bottom surface and diffusion in solid state. The stir zone and plastically deformed metal flow zone were influenced by scroll shoulder and smooth shoulder features. The tensile specimen of scroll shoulder was resulted to higher fracture load of 6381 N whereas the same was 4916 N in case of smooth shoulder. The interface of between plastically deformed metal flow zone and base material of AA6061-T6 can be considered as critical/weakest zone in case of friction spot extrusion. The variations of hardness were observed in stir zone, plastically deformed metal flow zone and thermo-mechanically affected zone in case of friction spot extrusion welding process.

Research paper thumbnail of Effect of tool profile on wear and mechanical behaviors of CeO2 and ZrO2-reinforced hybrid magnesium matrix composite developed via FSP technique

Journal of Manufacturing Processes, May 1, 2023

Research paper thumbnail of Improving the wear resistance and mechanical properties of hybridized AZ80 Mg/CeO2+ZrO2 surface composite by friction stir processing: Effect of pin geometry

Research paper thumbnail of Effect of tool profile on wear and mechanical behaviors of CeO2 and ZrO2-reinforced hybrid magnesium matrix composite developed via FSP technique

Journal of Manufacturing Processes

Research paper thumbnail of Post-processing treatments–microstructure–performance interrelationship of metal additive manufactured aerospace alloys: a review

Materials Science and Technology

Research paper thumbnail of Fabrication of AA6061/316 composites via a double pin FSP tool

Journal of Materials Research and Technology

Research paper thumbnail of Macro-/micro-mechanical interlocking modification on the performance of hybrid friction stir spot welded aluminum/acrylonitrile butadiene styrene joints

Research on Engineering Structures and Materials, 2021

To cite this article Ojo OO. Macro-/micro-mechanical interlocking modification on the performance... more To cite this article Ojo OO. Macro-/micro-mechanical interlocking modification on the performance of hybrid friction stir spot welded aluminum/acrylonitrile butadiene styrene joints.

Research paper thumbnail of Design, Fabrication and Structural Analysis of a 5 Tons Hydraulic Press and Mould Machine for Crucible Production

A hydraulic press machine comprising of the frame, cylinder, hand pump, and pressure gauge was de... more A hydraulic press machine comprising of the frame, cylinder, hand pump, and pressure gauge was designed, fabricated, and evaluated. The machine is manually operated and the frame was modeled using the Solidwork application software 2018 version. The maximum stress, maximum displacement, maximum strain, and factor of safety of the machine are 97.09 MPa, 0.337696 mm, 0.000361326, and 2.32 respectively. The performance of the developed machine was successfully carried out by using it to mould clay of different sieve sizes (0.6-4.75 mm) into crucible form with an applied maximum pressure of 100 bar. The results showed that the smaller the size of the sieve, the lower the pressure required for compaction, as a result, the hydraulic press designed is effective for clay compaction and the design is safe. The machine which was fabricated with local materials will enhance the production of suitable crucibles, thereby, reducing the over-reliance on the foreign crucible by small and medium sca...

Research paper thumbnail of Effects of materials positioning and tool rotational speed on metallurgical and mechanical properties of dissimilar modified friction stir clinching of AA5754-O and AA2024-T3 sheets

Results in Physics, 2021

Abstract The performance of the modified friction stir clinched and friction stir spot welded joi... more Abstract The performance of the modified friction stir clinched and friction stir spot welded joints of AA5754-O and AA2024-T3 Al alloy was improved by investigating the impact of material flow influencing parameters such as material positioning and tool rotational speed on the microstructure, mechanical and fracture behaviors of the joints. The results reveal that the positioning of a harder material (AA2024-T3) as the upper plate induces higher peak temperatures in the friction stir clinched (500 °C) and friction stir spot welded (475 °C) joints. This positioning favors inter-material mingling, grain coarsening with inherent higher dislocation density and tangles, and improved tensile failure loads in the AA2024-T3/AA5754-O joint than the AA5754-O/AA2024-T3 joint. The formation of partial weld-center defect declines in the AA2024-T3/AA5754-O at low tool rotational speed due to the better local heat build-up and geometric-differential flow effect in comparison with the AA5754-O/AA2024-T3 counterparts. The positioning of harder Al alloy on the top of a soft Al alloy is thus recommended for the improvement of modified friction stir clinched joints.

Research paper thumbnail of Effect of residual Alclad on friction stir spot welds of AA2219 alloys

Materials Testing, 2018

This paper aims to determine the role of in-nugget/residual Alclad in the friction stir spot weld... more This paper aims to determine the role of in-nugget/residual Alclad in the friction stir spot welds of 1.6 mm thick Alclad AA2219 aluminum alloy via an assessment of microstructure, mechanical properties and fracture modes of welds. Alclad redistribution/dispersion within the stir zone of the alloy is varied by using different tool profiles (pinless and conical pin tools) and welding parameter combinations. The results reveal that a pinless tool facilitates the retention of Alclad within the weld's effective joint line/width while no substantial residual Alclad is observed in the effective bonded width of a conical pin weld. The increase in tool depth improves the weld strength of a pinless weld. The fracture morphology of a pinless weld is influenced by the in-nugget Alclad content. Interfacial fracture with midpoint defect, interfacial fracture and nugget pull-out are the fracture modes of pinless welds while a conical pin weld fails by circumferential nugget shear failure. A d...

Research paper thumbnail of Diffusion brazing of IN738 to SiC ceramic with Ag-Cu-Ti powder: Effect of bonding time on metallurgical and mechanical properties

Research paper thumbnail of Mechanical and microstructural aspects of the hybrid joint of PP-C30S and 2219 aluminum alloy

Results in physics, Dec 1, 2020

Abstract In this work, 2219 aluminum alloy and PP-C30S sheets are welded using Threaded-hole Fric... more Abstract In this work, 2219 aluminum alloy and PP-C30S sheets are welded using Threaded-hole Friction Stir Spot Welding (THFSSW) and Probeless Friction Stir Spot Welding (PFSSW). The results revealed that the reaction layers were produced between the aluminum and polymer, irrespective of the process type. However, a larger reaction layer was formed in the THFSSW joint (37µm) as compared to that of the PFSSW joint (24µm), and this consequently in conjunction with the induced mechanical interlocking resulted in the increment of the weld strength from 290 N to 436 N. This implies that various frictional heat and adhesion force was generated during processes.

Research paper thumbnail of Friction spot extrusion welding-brazing of copper to aluminum alloy

Materials Letters, Feb 1, 2021

Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn... more Friction spot extrusion welding-brazing of pure copper to 5083 aluminum alloy sheet using pure Zn as interlayer has been elucidated. The effect of shoulder geometry on the microstructural characterizations and mechanical behavior of the joints was explored. Results indicated that changing the geometry of the shoulder from cylindrical to triangular not only enlarged the brazed zone from 14.98 lm to 19.65 lm, but also the tensile/shear strength had a rising trend and improved from 3268 N to 4398 N, which can be attributed to the larger brazed zone and complete filling of the pre-threaded hole in the joint produced by the triangular shoulder.

Research paper thumbnail of Friction stir processing of hybridized AZ31B magnesium alloy-based composites by adding CeO2 and ZrO2powders: mechanical, wear, and corrosion behaviors

Journal of materials research and technology, May 1, 2023

Research paper thumbnail of Probe-less friction stir spot processing (PFSSP) of AA5754/AA5083 joint by adding the B4C ceramics: Effect of shoulder features on mechanical properties and tribological behavior

Research paper thumbnail of Impact of multiple FSP passes on structure, mechanical, tribological and corrosion behaviors of AA6061/316 stainless-steel reinforced Al matrix composites

Surface & Coatings Technology, Oct 1, 2022

Research paper thumbnail of Weldability and mechanical properties of AA5083-H112 aluminum alloy and pure copper dissimilar friction spot extrusion welding-brazing

Vacuum, May 1, 2021

Abstract The friction spot extrusion welding-brazing (FSEW-B) process was employed to join AA5083... more Abstract The friction spot extrusion welding-brazing (FSEW-B) process was employed to join AA5083-H112 aluminum alloy and pure Cu via the use of a Zn interlayer to improve the mechanical properties of the dissimilar joint. The attained data indicated that not only FSEW-B led to the elimination of the keyhole, which is an intrinsic flaw of the Friction Stir Spot Welding (FSSW) process, but also the results showed that adding Zn interlayer was propitious to make less brittle intermetallic compounds (IMCs) like Al4Cu9 at the Cu/Al interface. More importantly, tensile shear results demonstrated an improvement in the strength and ductility of the FSEW-B weld sample (reached 156.2 MPa), which is attributable to the lack of keyhole defect and brittle IMCs in the joint.

Research paper thumbnail of Diffusion brazing of 321 stainless steel to IN738 using 54Ag-40Cu-5.0Zn-1.0Ni powder-mixture interlayer

Materials Letters, Aug 1, 2021

Research paper thumbnail of Influence of shoulder diameter on interfacial microstructure and mechanical behavior in dieless friction stir riveting of CP-Copper to 321 stainless steel

Research paper thumbnail of Friction spot extrusion brazing of copper to AISI 304 stainless steel with Zn interlayer: effect of shoulder surface modification

Archives of Civil and Mechanical Engineering, Feb 7, 2022

Research paper thumbnail of Effect of shoulder features during friction spot extrusion welding of 2024-T3 to 6061-T6 aluminium alloys

Archives of Civil and Mechanical Engineering, Jul 4, 2020

Friction spot extrusion welding process is successfully performed on dissimilar aluminum alloys o... more Friction spot extrusion welding process is successfully performed on dissimilar aluminum alloys of AA2024-T3 and AA6061-T6 under the influence of shoulder features. The joints were analysed by microstructural features and mechanical properties using conventional and advanced tools of visual inspection, optical microscopy, scanning electron microscopy, transmission electron microscopy, electron back scattered diffractions, tensile testing and hardness testing. The results revealed that the joining was obtained by combination of mechanical locking from extruded material of top surface to predrilled bottom surface and diffusion in solid state. The stir zone and plastically deformed metal flow zone were influenced by scroll shoulder and smooth shoulder features. The tensile specimen of scroll shoulder was resulted to higher fracture load of 6381 N whereas the same was 4916 N in case of smooth shoulder. The interface of between plastically deformed metal flow zone and base material of AA6061-T6 can be considered as critical/weakest zone in case of friction spot extrusion. The variations of hardness were observed in stir zone, plastically deformed metal flow zone and thermo-mechanically affected zone in case of friction spot extrusion welding process.

Research paper thumbnail of Effect of tool profile on wear and mechanical behaviors of CeO2 and ZrO2-reinforced hybrid magnesium matrix composite developed via FSP technique

Journal of Manufacturing Processes, May 1, 2023

Research paper thumbnail of Improving the wear resistance and mechanical properties of hybridized AZ80 Mg/CeO2+ZrO2 surface composite by friction stir processing: Effect of pin geometry

Research paper thumbnail of Effect of tool profile on wear and mechanical behaviors of CeO2 and ZrO2-reinforced hybrid magnesium matrix composite developed via FSP technique

Journal of Manufacturing Processes

Research paper thumbnail of Post-processing treatments–microstructure–performance interrelationship of metal additive manufactured aerospace alloys: a review

Materials Science and Technology

Research paper thumbnail of Fabrication of AA6061/316 composites via a double pin FSP tool

Journal of Materials Research and Technology

Research paper thumbnail of Macro-/micro-mechanical interlocking modification on the performance of hybrid friction stir spot welded aluminum/acrylonitrile butadiene styrene joints

Research on Engineering Structures and Materials, 2021

To cite this article Ojo OO. Macro-/micro-mechanical interlocking modification on the performance... more To cite this article Ojo OO. Macro-/micro-mechanical interlocking modification on the performance of hybrid friction stir spot welded aluminum/acrylonitrile butadiene styrene joints.

Research paper thumbnail of Design, Fabrication and Structural Analysis of a 5 Tons Hydraulic Press and Mould Machine for Crucible Production

A hydraulic press machine comprising of the frame, cylinder, hand pump, and pressure gauge was de... more A hydraulic press machine comprising of the frame, cylinder, hand pump, and pressure gauge was designed, fabricated, and evaluated. The machine is manually operated and the frame was modeled using the Solidwork application software 2018 version. The maximum stress, maximum displacement, maximum strain, and factor of safety of the machine are 97.09 MPa, 0.337696 mm, 0.000361326, and 2.32 respectively. The performance of the developed machine was successfully carried out by using it to mould clay of different sieve sizes (0.6-4.75 mm) into crucible form with an applied maximum pressure of 100 bar. The results showed that the smaller the size of the sieve, the lower the pressure required for compaction, as a result, the hydraulic press designed is effective for clay compaction and the design is safe. The machine which was fabricated with local materials will enhance the production of suitable crucibles, thereby, reducing the over-reliance on the foreign crucible by small and medium sca...

Research paper thumbnail of Effects of materials positioning and tool rotational speed on metallurgical and mechanical properties of dissimilar modified friction stir clinching of AA5754-O and AA2024-T3 sheets

Results in Physics, 2021

Abstract The performance of the modified friction stir clinched and friction stir spot welded joi... more Abstract The performance of the modified friction stir clinched and friction stir spot welded joints of AA5754-O and AA2024-T3 Al alloy was improved by investigating the impact of material flow influencing parameters such as material positioning and tool rotational speed on the microstructure, mechanical and fracture behaviors of the joints. The results reveal that the positioning of a harder material (AA2024-T3) as the upper plate induces higher peak temperatures in the friction stir clinched (500 °C) and friction stir spot welded (475 °C) joints. This positioning favors inter-material mingling, grain coarsening with inherent higher dislocation density and tangles, and improved tensile failure loads in the AA2024-T3/AA5754-O joint than the AA5754-O/AA2024-T3 joint. The formation of partial weld-center defect declines in the AA2024-T3/AA5754-O at low tool rotational speed due to the better local heat build-up and geometric-differential flow effect in comparison with the AA5754-O/AA2024-T3 counterparts. The positioning of harder Al alloy on the top of a soft Al alloy is thus recommended for the improvement of modified friction stir clinched joints.

Research paper thumbnail of Effect of residual Alclad on friction stir spot welds of AA2219 alloys

Materials Testing, 2018

This paper aims to determine the role of in-nugget/residual Alclad in the friction stir spot weld... more This paper aims to determine the role of in-nugget/residual Alclad in the friction stir spot welds of 1.6 mm thick Alclad AA2219 aluminum alloy via an assessment of microstructure, mechanical properties and fracture modes of welds. Alclad redistribution/dispersion within the stir zone of the alloy is varied by using different tool profiles (pinless and conical pin tools) and welding parameter combinations. The results reveal that a pinless tool facilitates the retention of Alclad within the weld's effective joint line/width while no substantial residual Alclad is observed in the effective bonded width of a conical pin weld. The increase in tool depth improves the weld strength of a pinless weld. The fracture morphology of a pinless weld is influenced by the in-nugget Alclad content. Interfacial fracture with midpoint defect, interfacial fracture and nugget pull-out are the fracture modes of pinless welds while a conical pin weld fails by circumferential nugget shear failure. A d...

Research paper thumbnail of Diffusion brazing of IN738 to SiC ceramic with Ag-Cu-Ti powder: Effect of bonding time on metallurgical and mechanical properties

Research paper thumbnail of Mechanical and microstructural aspects of the hybrid joint of PP-C30S and 2219 aluminum alloy

Results in physics, Dec 1, 2020

Abstract In this work, 2219 aluminum alloy and PP-C30S sheets are welded using Threaded-hole Fric... more Abstract In this work, 2219 aluminum alloy and PP-C30S sheets are welded using Threaded-hole Friction Stir Spot Welding (THFSSW) and Probeless Friction Stir Spot Welding (PFSSW). The results revealed that the reaction layers were produced between the aluminum and polymer, irrespective of the process type. However, a larger reaction layer was formed in the THFSSW joint (37µm) as compared to that of the PFSSW joint (24µm), and this consequently in conjunction with the induced mechanical interlocking resulted in the increment of the weld strength from 290 N to 436 N. This implies that various frictional heat and adhesion force was generated during processes.