Joining and microstructural development of Ni-Al-Ti sheets under ball collisions

Romankov, S.,Hayasaka, Y.,Shchetinin, I.V.,Yoon, J.M. Elsevier Science 2012 Acta materialia Vol.60 No.5

Ni-Al-Ti sheets were fabricated using a ball-collision technique at room temperature in an ambient atmosphere. The 0.5mm thick Ni, Al and Ti foils were stacked and fixed at the top of a vibration chamber and ball-treated for durations of between 5 and 30min. The microstructural evolution of the sheets was investigated as a function of the processing time and the mass of the ball. Joining of materials was considered to have occurred when materials at the interface plasticized, flowed and came into intimate contact under the high pressure developed by the ball collisions. The key parameters of the process were impact energy and processing time. Larger balls with higher impact energy were more effective for joining, and smaller balls were more effective for grain refinement. The transformation difference in grain refinement was attributed to the impact frequency, which appeared to be higher for the smaller balls. Ball collisions may have refined the grains of the Ni and Ti sheets to the nanometer scale, thereby destroying the initial rolling texture and inducing the formation of the fiber texture. The formation and stability of the <111> fiber texture in Ni were affected by the ball mass.

Deformation-induced plastic flow and mechanical intermixing of intentionally introduced impurities into a Ni sheet under ball collisions

Romankov, S.,Park, Y.C.,Shchetinin, I.V. Elsevier Sequoia 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.694 No.-

Ni and Ti sheets were subjected to intense plastic deformation through ball collisions initiated within a mechanically vibrated vial. The Ti and Ni sheets were cut to discs and affixed to opposite sides of the vial. In this report, we demonstrate the development of plastic flow and intermixing of components on the Ni sheet. Grinding media fragments were transferred and embedded into the Ni surface via ball milling. The ball collisions generated a strong material flow, inducing mechanical intermixing of the introduced components. When different materials flowed together, the components split and penetrated each other along the grain boundaries, forming parallel layers. Nanolaminated structures were developed throughout the elongation process via a slip mechanism. Shearing forces pushed the introduced material along the developing lamella interface, forcing it to slide. The face centered cubic (Fe, Ni) phase developed on the basis of the Ni lamella when nanosized elemental lamellae slid in parallel layers. Component intermixing began at strain localization zones, gradually spreading over the entire deformation-processed volume, resulting in the formation of a continuous alloyed layer. The formation of an alloyed surface layer significantly increased the hardness of the Ni sheet.

Fabrication of W and Mo layers with multi-modal structures on Ti sheets through intense plastic deformation induced by ball collisions

Romankov, S.,Park, Y.C.,Shchetinin, I.V. Elsevier 2019 Surface & coatings technology Vol.357 No.-

<P><B>Abstract</B></P> <P>Tungsten (W) and molybdenum (Mo) layers were fabricated onto Ti surfaces through intense plastic deformation induced by ball collisions initiated through a mechanically vibrated vial. The Ti disk was affixed to one side of the vial with either W or Mo targets affixed to the opposite side. During processing, ball collisions continually introduced the target material to the Ti surface, yielding mechanical alloying and formation of the desired alloyed layer. The as-fabricated W and Mo layers contained Fe component that was introduced from the milling media. The composition of the as-fabricated W layer corresponded to tungsten–iron heavy metal alloys. The introduction of Fe components could be favorable since the interaction between components resulted in the formation of complex multi-modal heterogeneous structures. There was an observed co-existence of alternating nanolaminated amorphous/crystalline structures, elemental flakes with polycrystalline nanograins, and nanocrystalline grains under 10 nm isolated by the amorphous phase. Structural formation in the W layer developed slowly compared to the Mo layer, which was related to the mechanical characteristics of the initial materials and the atomic reactivity with the Fe component. The as-fabricated surface alloyed W and Mo layers exhibited very high hardness values (883 HV and 933 HV, respectively) that were comparable to the hardness of tempered steel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> W and Mo layers were fabricated through intense plastic deformation induced by ball collisions. </LI> <LI> As-fabricated W and Mo layers exhibited complex multi-modal structures. </LI> <LI> Formation of the amorphous phase was related to crystal plane distortion. </LI> <LI> High hardness values were attributed to the formation of multi-modal structures. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Structural transformations in (CoFeNi)/Ti nanocomposite systems during prolonged heating

Romankov, S.,Park, Y.C.,Shchetinin, I.V. Elsevier 2018 Journal of alloys and compounds Vol.745 No.-

<P><B>Abstract</B></P> <P>A complex CoFeNi/Ti nanocomposite system with an average grain size of about 8 nm was fabricated on a Ti sheet under ball collisions. Heating experiments were performed at 400, 500, and 600 °C with hold times of up to 100 h at each temperature. The as-fabricated (CoFeNi)/Ti nanocomposite system demonstrated high thermal stability upon heating to 400 and 500 °C. Growth of the CoFeNi phases was retarded by closely spaced Ti particles. After heating to 600 °C, the system exhibited a bimodal nanograin structure due to coursing of the body-centered cubic (bcc) CoFeNi grains, which occurred more rapidly than with the face-centered cubic (fcc) CoFeNi grains. Upon heating, the diffusion that occurred between the phases tended to equilibrate the composition. Pairwise atomic interactions between the Co, Fe, and Ni components arose as chemical interactions in the corresponding binary alloy. The diffusive flux of elements in the system was outlined as Co from the fcc phase diffused into the bcc phase, Ni from the bcc phase diffused into the fcc phase, and Fe from the fcc phase diffused into the bcc phase. The activation energy for the reaction was calculated using time dependence curves of saturation magnetization. The activation energy coincided very closely with the value for the grain boundary diffusion activation energy for the Co, Fe, and Ni binary systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> (CoFeNi)/Ti nanocomposite system demonstrated high thermal stability during heating. </LI> <LI> Growth of the CoFeNi phases was retarded by closely spaced Ti particles. </LI> <LI> After heating to 600 °C, the system exhibited a bimodal nanograin structure. </LI> <LI> The diffusive flux of elements in the system was outlined. </LI> <LI> Activation energy was calculated using time dependence curves of magnetization. </LI> </UL> </P>

Atomic-scale intermixing, amorphization and microstructural development in a multicomponent system subjected to surface severe plastic deformation

Romankov, S.,Park, Y.C.,Shchetinin, I.V.,Yoon, J.M. Elsevier Science 2013 ACTA MATERIALIA Vol.61 No.4

Al, Zr, Ni, Co, Fe and Cr were introduced into a Cu plate using ball collisions to fabricate a multicomponent composite layer. The application of severe plastic deformation induced by repeated ball collisions with the as-fabricated composite layer led to intermixing of the components and the formation of a surface alloyed layer on the Cu plate. The microstructural development of the surface alloyed layer was a function of the treatment time. After 1h of treatment, an alternating laminated amorphous/crystalline composite structure with a mean lamellar thickness of ~10nm was formed as a result of the combined effects of the deformation-induced plastic flow, interdiffusion and intermixing of the elements. The crystalline lamellae were related to the multicomponent non-equilibrium solid solution based on the Cu crystal structure. Increase in treatment time to 4h led to structural changes. The crystalline lamellae underwent refinement that was attributed to dislocation activity and were subdivided into interlamellar blocks. The amorphous lamellae tended to disappear. A body-centered cubic (bcc) Fe solid solution was formed in the layer. Nucleation and growth of bcc Fe precipices in amorphous and crystalline phases were related to increase in Fe content in the layer, which increased with treatment time. The hardness of the as-fabricated layer was almost ten times that of the initial Cu plate.

Mechanical intermixing of elements and self-organization of (FeNi) and (CoFeNi) nanostructured composite layers on a Ti sheet under ball collisions

Romankov, S.,Park, Y.C.,Shchetinin, I.V. Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.653 No.-

<P><B>Abstract</B></P> <P>A Ti sheet was subjected to intense plastic deformation through ball collisions initiated in a mechanically vibrated vial. The Ti was cut into a disk shape and fixed on one side of the vial with either Ni or Co disks fixed on the opposite side. The objective here was to intentionally use the Ni and Co disks as a source of Ni and Co impurities, while steel balls were to serve as a source for Fe impurities. During processing, ball collisions continuously introduced impurities from the grinding media onto the Ti surface, caused strong material flow, and induced mechanical intermixing of the elements, resulting in self-organization of the polycrystalline nanocomposite structure with an average grain size of about 8 nm. The phase composition of the alloyed layers was dependent on the material transferred into the system. When both Ti and Ni disks were subjected to ball collisions, the alloyed layer was composed of fcc (Fe,Ni) and Ti grains. However, when the Ni disk was subsequently replaced with Co, the layer consisted of bcc and fcc CoFeNi along with Ti grains. The fcc (Fe,Ni) phase was formed on the basis of the fcc Ni crystal structure, while the bcc Fe structure served as the basis for the bcc CoFeNi phase. The as-fabricated nanocomposite layers were extremely hard (∼900 HV on the average), and a nearly three-fold increase was observed in the surface hardness of the Ti sheet after processing. The as-fabricated layers exhibited magnetic properties representative of soft-magnetic materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ball treatment technique can be effectively employed for surface alloying. </LI> <LI> Strong material flow and mechanical intermixing results in self-organization. </LI> <LI> Technique allows us to fabricate soft-magnetic nanocomposite layers in one operation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Mechanical intermixing of components in (CoMoNi)-based systems and the formation of (CoMoNi)/WC nanocomposite layers on Ti sheets under ball collisions

Romankov, S.,Park, Y.C.,Shchetinin, I.V. Elsevier BV * North-Holland 2017 Applied Surface Science Vol.422 No.-

<P><B>Abstract</B></P> <P>Cobalt (Co), molybdenum (Mo), and nickel (Ni) components were simultaneously introduced onto titanium (Ti) surfaces from a composed target using ball collisions. Tungsten carbide (WC) balls were selected for processing as the source of a cemented carbide reinforcement phase. During processing, ball collisions continuously introduced components from the target and the grinding media onto the Ti surface and induced mechanical intermixing of the elements, resulting in formation of a complex nanocomposite structure onto the Ti surface. The as-fabricated microstructure consisted of uniformly dispersed WC particles embedded within an integrated metallic matrix composed of an amorphous phase with nanocrystalline grains. The phase composition of the alloyed layers, atomic reactions, and the matrix grain sizes depended on the combination of components introduced onto the Ti surface during milling. The as-fabricated layer exhibited a very high hardness compared to industrial metallic alloys and tool steel materials. This approach could be used for the manufacture of both cemented carbides and amorphous matrix composite layers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Formation of (CoMoNi)/WC layers arises from mechanical intermixing of components. </LI> <LI> Structure consists of WC particles embedded within an integrated metallic matrix. </LI> <LI> Matrix phases and atomic reactions are dependent on combination of target materials. </LI> <LI> Amorphization arises from compositional changes and distortions of the Co lattice. </LI> <LI> Variation in hardness between layers is related to matrix structure of the layers. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>