In this study, effects of the milling time on densification, microstructural characteristics and mechanical properties of Cu–SiC nanocomposite produced by high energy mechanical milling and ...conventional sintering process are investigated. Cu–SiC powder was milled for different durations and then cold compacted under 800 MPa pressure followed by conventional sintering at 900 °C under argon atmosphere for 1h. The microstructural characterization was conducted by x-ray diffraction (XRD), scanning electron microscope (SEM), and scanning transmission electron microscope (STEM). The highest densification for the composite powder was obtained at a short milling time, where the powder showed flake morphology and lower strain-hardening. By increasing the milling time, the size of the Cu matrix grains refined and the level of microstrain and microhardness of the nanocomposite improved. The incorporation of the nanoparticles in the Cu matrix increased the microhardness of the copper. This effect was more evident in lower milling durations.
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•Effects of milling time on sintering and structure of Cu–SiC nanocomposite were studied.•Using flake Cu–SiC powders prepared through short-time milling resulted in a higher densification.•Strengthening by SiC nanoparticles was more effective in lower milling durations.•Mechanical milling improves the matrix thermal stability at high temperatures.
During the mechanical milling of powders for the production of metal matrix composites, the work hardening of metals occurs along with the distribution of reinforcing particles, which reduces the ...ductility and formability of the powders. The use of milling for a short time, in addition to creating homogeneity for reinforcing particles on the surface of flaky metal particles, causes less work-hardening of powders and allows better densification of composite powders. In this research, aluminum-carbon nanotubes (Al-CNT) nanocomposites were fabricated using flake powder metallurgy and hot pressing method. The homogeneous distribution of carbon nanotubes in the aluminum matrix and density close to the theoretical density were obtained through the manufacturing process. After the addition of carbon nanotubes, the grain size of matrix phase reduced from 106 nm to 56 nm in 4 vol% reinforcement. The increase of carbon nanotubes at 2 and 4 vol% increased the yield strength and compressive strength from 176 MPa and 201 MPa to 241 MPa and 251 MPa and reduced the fracture strain from >20% to 4%, respectively. The increased strength depends on the fine grains of the matrix phase, the proper distribution of carbon nanotubes and their strengthening effect.
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•The Al-CNT composites were successfully fabricated by flake powder metallurgy method.•The effect of CNT content on densification of the composite was investigated.•By increasing the vol% of CNT, the grain size of the matrix decreases.•Addition of 4 vol% CNT to the NS-Al increased the yield strength about 36%.•The grain size is the most influencing parameter on the strengthening.
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•Synthesis of new Ti-Cu alloy by mechanical alloying and sintering process.•Ultra-high hardness of 10 GPa, acceptable toughness of 8.14 MPam1/2.•∼98 % anti-bacterial rate against S. ...aureus and E. coli.•Excellent cell viability to MG-63 cells, and high osteoblast formation rate.•Corrosion behavior of the alloy was slightly lower than cp-Ti.
The demands for high-performance biomaterials are driving the development of new metallic alloys with improved mechanical and biological responses. In this study, a nanocrystalline Ti-Cu intermetallic alloy was prepared by a powder metallurgy route, and its application as an orthopedic material was evaluated by the microstructural, mechanical, corrosion, antibacterial, cytotoxicity and osseointegration examinations. Microstructural characterization revealed the formation of TiCu and Ti2Cu3 as major phases with 23 nm grain size in the structure of the alloy. The synthesized alloy exhibited ultra-high hardness of 10 GPa, acceptable toughness of 8.14 MPam1/2, a ∼98 % anti-bacterial rate against S. aureus and E. coli, excellent cell viability to MG-63 osteosarcoma cells, and high osteoblast formation rate, which indicate a great potential of this alloy for biomedical application.
Copper based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were fabricated via mechanical milling followed by hot pressing ...technique. Microstructures of the powders and consolidated materials were studied using scanning electron microscope, X-ray diffraction, Raman spectroscopy, and scanning transmission electron microscope. Microstructural characterization of the materials revealed that the addition of nanosized silicon carbide reinforcement lowered the grain growth rate and enhanced the homogenization during mechanical milling. Microhardness measurements and compression test showed considerable improvements in mechanical properties of the composites due to the addition of nanoparticulates and the grain refinement. The strength of the composite materials was discussed using theoretical models of the Hall-Petch, Orowan, and thermal mismatch mechanisms to determine the contribution of each mechanism in total strength.
In this research, tribological properties of bulk Ti-Cu intermetallic alloy as a new biomedical material produced via mechanical alloying as well as pressureless sintering were investigated. Ti and ...Cu powders mixture (1:1 molar ratio) was mechanically milled for various times and then sintered in an argon atmosphere. Microstructural characterization revealed TiCu and Ti2Cu3 as primary phases and Ti2Cu and TiCu4 as secondary phases in the sintered alloy. Results of wear tests showed that Ti-Cu intermetallic alloy has much higher wear resistance and lower friction coefficient compared to commercially pure titanium against hard WC counterface. Wear and friction properties of the alloy were considerably improved by prolonging alloying time due to refinement of grain size and increase of Ti2Cu3 phase amount in the sintered alloy. The examinations presented here demonstrate that the Ti-Cu intermetallic alloy can be a very proper substitute for costly biomedical implant materials due to its very high wear resistance and low friction coefficient.
•Ti-Cu alloy as a new biomedical material was synthesized by powder metallurgy route.•The amount of Ti2Cu3 phase in the produced alloy enhanced at higher milling times.•Tribological properties of Ti-Cu alloy were studied.•Ti-Cu alloy showed good wear resistance and lower FC against WC counterface.•The higher amount of Ti2Cu3 phase results in the higher wear resistance.
Hybrid-reinforced metals are novel composite materials in which nano-phases including nanoparticles and nanotubes/nanosheets are used simultaneously to reinforce metals or alloys to enhance physical, ...mechanical, wear and other properties. In this research, Cu/(CNT-SiC) hybrid nanocomposite was synthesized using flake powder metallurgy and spark plasma sintering method and the effects of hybrid reinforcements on microstructural, wear and corrosion properties of the developed material were investigated and compared with those of copper. Microstructural characterization showed reduction of average grain size from 419 to 307 nm and increase of low angle grain boundaries with the introduction and homogeneous dispersion of hybrid reinforcements. Mechanical tests indicated that the addition of hybrid SiC and CNT reinforcements substantially increased microhardness and reduced wear rate and friction coefficient of the Cu. Also, polarization and EIS tests revealed the suppressing of the anodic dissolution of the matrix, hindering the oxygen reduction reaction and 62.5% improvement of corrosion rate for the composite material. The effects of hybrid nano-reinforcements are presented and discussed.
TiC-Graphene/Cu hybrid nanocomposites were fabricated from a mixture of Cu, Ti and Graphite (C) powders in three different TiC percentages (20, 40, 60 vol%) by two-step ball milling for (8 + 8) h and ...in-situ reactive sintering. The microstructure of the synthesized composites was characterized using x-ray diffraction (XRD), scanning/ transmission electron microscopy (SEM/TEM), and mechanical properties were evaluated by microhardness and wear tests. Microstructural studies revealed that the fabricated composites were composed of a copper matrix together with the homogeneous distribution of the TiC nanoparticles and graphene layers (as un-reacted carbon) with minimal porosities. The TiC addition led to a reduction in the density of sintered composites. With the increasing of reinforcement’s volume fraction, microhardness of the nanocomposites increased. Cu-40 vol% TiC nanocomposite exhibited the lowest coefficient of friction of about 0.17 and the highest wear resistance against WC counterface.
Ultrafine-grained Al-CNT (2 and 4 vol%) composites were successfully fabricated using the flake powder metallurgy and hot pressing route, and the microstructure and tribological properties of the ...produced composites were studied. The results showed that the coefficient of friction and the wear rate of Al decrease with the addition of the CNT reinforcement. A carbon-rich film was formed on the worn surfaces during wear test, which prevented the Al oxidation and yielded the self-lubricating effect for the composites. This improvement in the wear behavior of the composites can be attributed to the simultaneous effects of the ultrafine-grained matrix and strengthening and self-lubricating properties of the uniformly dispersed and undamaged CNT in the flake powder metallurgy method.
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•Self-lubricating Al-CNT composites were fabricated by flake powder metallurgy.•Homogenously dispersed and undamaged CNTs were introduced to Al matrix.•CNTs play a major role in improving wear properties by forming a CNT-rich film.•Al-4 vol% CNT composite exhibited the lowest wear and friction.•The theoretical friction coefficient of the composites was calculated.
•Self-lubricating Cu-CNT composites were fabricated by flake powder metallurgy.•CNTs play a major role in improving wear properties by forming a CNT-rich film.•Cu- 4vol% CNT composite exhibited the ...lowest wear and friction.•A correlation was proposed for the calculation of the friction coefficient.
Cu-CNT composites were fabricated by a flake powder metallurgy method, and their microhardness, electrical conductivity, frictional and wear properties were investigated. Homogenous distribution of CNTs in fine-grained Cu matrix was obtained using this process. Microhardness increased with the addition of CNT vol% up to 8% to the Cu matrix, while the conductivity decreased to 79.2 IACS %. Results showed that CNTs play a major role in improving wear resistance by forming a CNT-rich film that acts as a solid lubricant layer. In the synthesized composites, Cu- 4vol% CNT composite exhibited the best wear and friction properties. The dominant wear mechanisms for the Cu-CNT composites were plastic deformation, abrasion, and flake formation-spalling. Also, a newly modified correlation was proposed for the theoretical calculation of the friction coefficient of Cu-CNT composites consisting agglomerated CNTs.
In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was ...investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties for biomedical applications.
•Ni-50 mol. % Ti alloy was successfully sintered via 15 min microwave-assisted heating.•HRTEM analysis revealed major phases of NiTi– B2) and Ni3Ti in the alloy structure.•The highest microhardness of 750 H V was indicated for the sample sintered at 1100 °C.•The high hardness was attributed to the nanostructuring and Ni3Ti phase formation.
