By means of the mechanical alloying (MA) method, Al and Ti+Al coatings were deposited on Ti alloy substrates. During the mechano-activation processing, the substrate surface was impacted by a large ...number of flying balls along with particles of powder. The repeated ball collisions with the substrate resulted in the deposition of powder on its surface. MA technique produced Ti+Al coating with a thickness of 200 μm and Al one with a thickness of 50 μm after 2 h milling at room temperature. The as-synthesized coatings showed structures with high apparent density and free of porosity. The surface morphology of the MA-coatings was very rough. Annealing treatment led to the leveling of this uneven morphology. Annealing at temperatures ranging between 600 °C and 1100 °C gave different aluminide phases on the samples. In the case of Al coating, Al3Ti and Ti3Al compound were observed upon heating up to 1100 °C. In the case of Ti+Al coating, Al3Ti, Al2Ti, TiAl and Ti3Al were formed on the surface.
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.
•(CoFeNi)/Ti nanocomposite system demonstrated high thermal stability during heating.•Growth of the CoFeNi phases was retarded by closely spaced Ti particles.•After heating to 600 °C, the system exhibited a bimodal nanograin structure.•The diffusive flux of elements in the system was outlined.•Activation energy was calculated using time dependence curves of magnetization.
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.
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.
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•Development of plastic flow and formation of nanolaminated structure are shown.•When materials flowed together, the components split and penetrated each other.•Nanolaminated structures were developed throughout the elongation process.•Shear stress pushed the introduced material along the interface, forcing it to slide.•(Fe, Ni) phase developed when nanosized elemental lamellae slid in parallel layers.
•Aluminizing a Ni sheet was performed by mechanical alloying.•Technique allows us to apply Al layer from both sides of a sheet in one operation.•The Al layer consisted of Al grains with an average ...size of about 40nm.•The hardness of the fabricated Al layer was 10 times that of the initial Al plate.•The ball collisions destroyed the initial rolling texture of the Ni sheet.
Aluminizing a Ni sheet was performed through severe plastic deformation induced by ball collisions. The Ni sheet was fixed in the center of a mechanically vibrated vial between two connected parts. The balls were loaded into the vial on both sides of the Ni disk. Al disks, which were fixed on the top and the bottom of the vial, served as the sources of Al contamination. During processing, the Ni sheet was subject to intense ball collisions. The Al fragments were transferred and alloyed to the surface of the Ni sheet by these collisions. The combined effects of deformation-induced plastic flow, mechanical intermixing, and grain refinement resulted in the formation of a dense, continuous nanostructured Al layer on the Ni surface on both sides of the sheet. The Al layer consisted of Al grains with an average size of about 40nm. The Al layer was reinforced with nano-sized Ni flakes that were introduced from the Ni surface during processing. The local amorphization at the Ni/Al interface revealed that the bonding between Ni and Al was formed by mechanical intermixing of atomic layers at the interface. The hardness of the fabricated Al layer was 10 times that of the initial Al plate. The ball collisions destroyed the initial rolling texture of the Ni sheet and induced the formation of the mixed 100+111 fiber texture. The laminar rolling structure of the Ni was transformed into an ultrafine grain structure.
•Microstructural transformation in amorphous/crystalline structure was studied.•Amorphous/crystalline structure was stable during heating up to 600°C.•Transformation of the amorphous/crystalline ...structure occurred at temperatures above 600°C.•Heating of the non-equilibrium multicomponent system produced complex patterns.•Heating at 900°C produced a new morphologically complex nanocomposite structure.
A nanolaminated amorphous/crystalline composite structure with a mean lamellar thickness of around 10nm was fabricated on a Cu plate. The crystalline phase was a multicomponent non-equilibrium face-centered cubic (fcc) Cu(CoFeNi) solid solution, and the amorphous phase was a Zr-based compound containing Al, Cu, and Fe. The composite’s thermal stability and microstructural transformation was studied over the temperature range of 200–900°C. The lamellae maintained their shape during heating up to 600°C. Transformation of the structure began with separation of the elements inside the crystalline lamellae. In early stages of the transformation, hardening occurred. At 600°C, an interconnected CoFe phase started to appear with an ordered body-centered cubic (bcc) crystal structure. When the temperature was increased further, the nanolaminated structure degraded and the bcc CoFe phase grew. At 750°C, the bcc CoFe phase formed a complex network that surrounded the formerly amorphous regions, and the bcc CoFe phase started transforming to the fcc configuration. The Cu atoms segregated to the grain boundaries of the fcc CoFe(Ni) phase. The amorphous phase gradually crystallized into nanometer-sized polycrystalline grains that were attributed to the Zr(Al)O2 phase. As a result of these transformations, heating at 900°C produced a morphologically complex nanocomposite structure consisting of branched grains of Zr(Al)O2 and fcc CoFe(Ni) with Cu inclusions. When the nanolaminated structure had completely transformed, the layer was softer than it had been in the initial annealing steps, but was still almost five times as hard as the initial Cu plate.
▶ Cu–SiC surface composite was fabricated by ball collisions at room temperature after 15
min treatment. ▶ Composite formation was the result of mechanical mixing of the plasticized Cu and the SiC ...particles. ▶ Ball collisions refined the grains near the surface to the nanometer scale. ▶ Initial rolling texture of the Cu plate was completely destroyed by 15
min of ball collisions. ▶ Surface hardness of the composite layer was almost twice that of the initial Cu plate.
A nano-grained Cu–SiC surface composite was fabricated on a Cu plate precoated with SiC particles at room temperature after 15
min treatment using ball collisions. The composite formation was the result of mechanical mixing of the plasticized Cu and the SiC particles. Ball collisions refined the grains near the surface to the nanometer scale and destroyed the initial rolling texture of the Cu plate. The surface hardness of the composite layer was almost twice that of the initial Cu plate.
A vibration technique was used to fabricate Ti–Al coatings. During mechanical milling, the sample surface was subjected to high-energy ball impacts. The powder particles trapped between the balls and ...substrate became cold-welded to the substrate surface. The repeated substrate-to-ball collisions flattened the particles and forged them onto the surface into a bulk material. The coating thickness and roughness can be optimized by the combinations of key factors such as the ball-to-powder weight ratio, milling duration, and ball size. The development of the coating structure is associated with the milling intensity. A Ti–Al coating formed rapidly as the milling intensity increased. Prolonged milling led to structural refinement of the top coating layer. The grain size may reach the nanometer scale under prolonged milling. The ball size was critical to coating formation.
•Balls were coated with Al by mechanical alloying.•Cu sheet was treated by balls coated with Al.•Al was introduced into the Cu sheet.•Deformation induced intermixing of elements.•Hardness increased ...more than four times.
Cu sheet was alloyed with Al using ball collisions at room temperature and ambient atmosphere. Al was introduced into the Cu sheet as contamination from the grinding media. The idea here was first to coat the balls with Al by mechanical alloying and treated the surface of the Cu sheet using ball collisions. The Al debris from the grinding media was first to adhere to the Cu sheet under the ball collisions and then the deformation-induced diffusion and intermixing of the elements resulted in the formation of the Cu(Al) solid solution. The size of nanocrystalline grains after treatment ranged between 10nm and 50nm and an average of about 20nm. The hardness of the Cu sheet after the treatment was increased more than four times.
► Al–SiC surface composite was fabricated by ball collisions at room temperature. ► Structural formation was associated with strain accumulation induced by ball impacts over time. ► Composite ...formation was the result of mechanical mixing of the plasticized Al and SiC. ► Initial rolling texture of the Al plate was completely destroyed by 10min of ball collisions. ► Hardness of the composite became almost three times that of the initial Al plate.
An Al–SiC surface composite was fabricated on an Al surface precoated with SiC particles by ball collisions at room temperature in an ambient atmosphere. The formation of the composite was investigated at various treatment intervals between 5 and 30min. The structural formation was affected by the treatment time, which was associated with the accumulation of strains introduced by ball collisions. In the strained zone, Al became plasticized and flowed. The Al plastic flow trapped, occluded and transported the SiC particles. Ball collisions refined the coarse grains of the initial Al plate and the SiC particles. The initial rolling texture of the Al plate, consisting of {112}〈111〉 and {110}〈112〉 orientations, was completely destroyed by 10min of ball collisions. After 15-min treatment, the composite structure consisted of three phases: ultrafine-grained Al matrix, coarse SiC reinforcement and nanocrystalline Al–SiC composite interlayers. The hardness of the as-fabricated composite was increased almost threefold compared to that of the initial Al plate.
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