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The interest for lightweight and high-temperature materials for critical innovative applications is expanding in numerous modern industries. Reinforcing ceramic particles with micro/nano-scale sizes into titanium alloys is distinguished, thereby increasing the hardness and wear resistance. Alternatively, reduction in particles sizes also helps in increasing the strength, ductility, and creep resistance of the reinforced materials. Nano-ceramic has significant improvement in mechanical properties of a material, which makes it practically a good reinforcement in metal composites. Recent advancement in nanotechnology area demands innovative improvement in metal matrix composite for critical and functional applications. The effects of micro/nanomaterial dispersion in the metal matrix composite are spoken about and the formation of unexpected interfacial reaction on these properties. Powder metallurgy is a process where powder materials are being compacted or sintered in the furnace with the perspective of accomplishing higher densities. Spark plasma sintering techniques have a favorable condition over other sintering methods since it tends to decrease the sintering time with high temperatures, attaining higher densities, microstructural evolution, and the tendency to improve the mechanical properties of the material. This review focuses on the fabrication and mechanical properties of titanium alloy strengthening with micro/nano-ceramics.

Although SPS has been studied for a rapidly growing number of materials, there is limited number of researches on the fabrication and microstructural characterization of stainless steels processed by SPS. This article reviewed and provided a critical discussion on the mechanical alloying (MA) and spark plasma sintering (SPS) of dispersion-strengthened stainless steel with emphasis on process parameters, reinforcement efficiencies, microstructural evolutions, and mechanical properties. The influence of spark plasma sintering process parameters on microstructure, phase evolution, and mechanical properties of reinforced stainless steels is reviewed in this work. The role of alloying elements and ceramic reinforcements, their dispersion into the stainless steel matrix, and the importance of matrix-reinforcement interface are highlighted. Current and potential areas of applications of PM stainless steel and suggestions for future research are discussed in this paper.

Duplex stainless steel (SAF 2205) reinforced with various weight percent of titanium nitride (TiN) nanoparticles is fabricated in vacuum via spark plasma sintering (SPS) using optimized SPS process parameter of 1150 °C for 10 min and 100 °C/min. The influence of TiN addition on the densification mechanism, microstructure, hardness, and fracture surface of the fabricated duplex stainless steel composite fabricated is evaluated. The results indicate even dispersion of the TiN nanoparticles in the steel matrix during turbular mixing. The displacement and shrinkage rates show three densification stages relating to micro-nanoparticle rearrangement, plastic deformation of the particles, and rapid densification of the composite. The microstructure revealed ferrite, austenite, and TiN phase at grain boundaries. There was phase transformation of ferrite to austenite with the addition of TiN nanoparticles due to diffusion of nitrogen as austenite stabilizer. The evolution of Cr 2 N nitride precipitates along grain boundary, and a dendrite-like austenite structure was evident during sintering. The hardness of the composite was enhanced while the density decreased with TiN content. The fracture surface analysis showed a transition from ductile to brittle fracture with increase in TiN addition.

The extensive application of titanium alloys is delimited as their erosion wear properties deteriorate when exposed to erosive and harsh environments. The present research investigates the effects of TiN additions (2, 4, and 6 vol.%) on the Ti-6Al-4V alloy prepared by spark plasma sintering technique. Erosion wear behaviour of the composites was investigated by high-velocity solid particle erosion test and tribometer pin-on-disc friction module method. The duration of the test was 10 min, while the mass loss of the sample was recorded after 2-min interval. The surface analysis and phase identifications of the sintered composites were examined by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Microstructural analysis revealed a transformation from lamellar with β grain boundaries in Ti-6Al-4V alloy to bimodal structures upon addition of TiN nanoparticles. XRD patterns of the alloy indicated an increase in diffraction peaks from lower intensity to high intensity with an increase in TiN nanoparticle content. Erosion is visible in Ti-6Al-4V alloy, 4 and 6 vol.% TiN, but less severe with 2 vol.% TiN addition for all the test times. However, this is due to grain detachment of the hard phase regions between the matrix and the reinforcing phase of the composites. The results showed the presence of micro-voids on the eroded surfaces. It was found that Ti-6Al-4V alloy with TiN nanoparticle addition was resistant to erosion wear, while the recorded steady-state friction coefficients for all the samples range from 0.2 to 0.4. However, an increase in microhardness values ranges from 342 to 513 HV 0.1 .

The impacts of Cr-TiB 2 addition on densification, hardness, microstructure, phase transformation, and corrosion were examined. The results indicated an even and uniform dispersion of TiB 2 particles in the titanium matrix, with no noticeable interfaces throughout the sintering process. The relative density of the sintered titanium-based composites dropped, with an increase in TiB 2 percentage. The microhardness result indicated that Ti6Al4V has 326 HV 0.5 , while the maximum hardness was 598 HV 0.5, produced from 20 wt.% TiB 2 ceramic particles. The Ti6Al4V alloy depicts α-phase forms parallel plates in the prior β-grain borders and expands into the β-grain to create α-colonies, while the addition of 5–20 wt.% Cr-TiB 2 resulted in a microstructural transformation characterized by equiaxed α-precipitates embedded within the β-phase matrix, for all samples. The electrochemical behaviour revealed that the E corr decreased as TiB 2 increased, while the i corr was higher. However, samples containing 5Cr and 5Cr-5TiB 2 moved to a more positive E corr region, whereas the i corr altered to a more negative area. This meant that the presence of ceramic reinforcements increased the corrosion resistance of the alloys and that higher concentrations of titanium diboride provided less protection against ion attack in a chloride environment.

The limitations of aluminium in most engineering applications has led to the development of aluminium matrix composites with improved microstructural and mechanical properties. Nanoindentation techniques was used in assessing the mechanical properties of fabricated aluminium matrix composites with ferrotitanium and silicon carbide as reinforcements. Results from nanoindentation experiments shows the dependence of modulus of elasticity, microhardness and contact depth on the dispersion of ferrotitanium and silicon carbide reinforcements within the aluminium matrix. Highest nanohardness value was observed in composite with 7 wt. % silicon carbide, while the lowest elastic modulus was recorded in as-cast aluminium. Further analysis of specimens confirmed a decrease in maximum penetration depth with respective increase in the addition of silicon carbide reinforcements in the fabricated composites.

This research reports on the microstructural characterization and nanomechanical evaluation of hybrid aluminium-based composite, fabricated by reinforcing pure aluminium matrix with zirconia (ZrO2) and ferrotitanium (TiFe) particles. The composites were consolidated using the spark plasma sintering technique, and the properties of the reinforced composites were examined and compared with pure aluminium samples fabricated using the same sintering parameters. The formation of new phases in the hybrid composites was ascertained using the X-ray diffraction technique, while the morphologies of the starting powders and as-sintered specimens were analysed using optical and scanning electron microscopes. Mechanical tests such as Vickers microhardness and frictional coefficient were determined to ascertain the respective strength and tribological performance. Nanoindentation test was also carried out to evaluate the nanomechanical properties such as penetration depth, elastic modulus, work indentation, and indentation creep. The results from this study revealed that mixing and sintering the admixed powders at sufficiently high temperature resulted in the formation of new phases which contributed to improved mechanical performance of the hybrid composites. The absence of pinning effect in loading and unloading curves from the nanoindentation test conducted confirmed the homogeneous dispersion of the reinforcement particles. Overall, the sample reinforced with 5% TiFe and 5% ZrO2 exhibited the most improved mechanical properties, while the unreinforced aluminium sample recorded the least mechanical and nanomechanical performance.

In this present work, the influence of solution heat treatment on microstructure, mechanical and wear properties of a hot-rolled 2205 duplex stainless steel (DSS) was investigated. The DSS samples were subjected to solution heat treatment at different temperature of 1000, 1040, 1080 and 1150 °C, held for 30 min and quenched in water. The microstructure and phase evolution of the as-received and solution heat-treated samples were analyzed using the optical microscope, scanning electron microscope, and x-ray diffraction. Tensile and wear properties were also studied. The result shows that the DSS has characteristic lamellae microstructure consisting of alternating bands of ferrite (δ) and elongated austenite (γ) with intermetallic precipitates nucleated around the ferrite region. The as-received samples have a higher hardness, tensile strength, yield strength and exhibit a high wear resistance compared to the solution heat-treated samples. The worn surface morphology revealed a mixed-mode of adhesive and abrasive wear mechanisms.

The influence of ceramic (TiN and TiB 2 ) particles on the densification, microstructure, wear, and nanoindentation behavior of titanium matrix composites produced by spark plasma sintering was investigated. The results showed that the relative density of the Ti6Al4V-Ni-Cr-matrix composite with TiN and TiB 2 was reduced from 99.51 to 95.33%. The microstructural analysis revealed that the reinforcements were dispersed uniformly within the composite, demonstrating the existence of lamellar (α and β phase) and bimodal structures. The average microhardness value gradually increased from 378 to 707 HV 0.2, while the coefficient of friction ranged between 0.3 and 0.65. Furthermore, the material resisted the wear mechanism with improved wear resistance. The decreased frictional coefficient exhibited by the reinforced composite might be attributed to the oxide-layer formation, which served as a lubricant reducing friction between the two gliding surfaces of the material. The nanohardness values ranged from 6363.3 to 10,343 MPa, while the reduced-elastic-modulus values varied from 122.9 to 158.93 GPa.

The quest to consistently develop improved materials for direct application in automotive, aerospace, and other industries has led to the synthesis of titanium-based composites—with current research efforts being directed toward the utilization of carbon nanotubes (CNTs) as reinforcement. CNTs constitute an outstanding reinforcement for titanium-based matrixes, owing to their extraordinary physical, electrical, mechanical, and thermal properties. Powder metallurgy (PM) routes have been adjudged the most promising technique for synthesizing CNT-reinforced titanium. However, past reviews have highlighted various PM techniques, reinforcement efficiency, and effective methods for dispersing CNTs in metal matrixes. Among the various PM techniques, spark plasma sintering (SPS) has gained popularity in the synthesizing of titanium-based nanocomposites (TMNCs). Hence, this review focused on past works on the SPS of TMNCs reinforced with CNTs. The properties of CNTs, their fabrication method, their densification mechanism, and the mechanical properties of sintered TMNCs were discussed in detail.