Ti Metal Matrix Composites Research Articles

Preparation and Characterization of Ti‐6‐4 and Ti‐8‐1‐1 Metal Matrix Composites with High Specific Stiffness Using Powder Hot Extrusion and Arc Remelting

Titanium alloys with high stiffness are crucial for aerospace engineering and are often fabricated using additive manufacturing (AM) methods like arc or laser techniques. These high energy processes alter the microstructure and mechanical properties. To enhance stiffness, TiC and B4C are added to Ti–6Al–4V and Ti–8Al–1Mo–1V alloys via powder hot extrusion. The resulting metal matrix composites (MMCs) are analyzed in both their as‐extruded and heat‐treated states for microstructure and mechanical properties. To simulate an AM process, samples are remelted using a gas tungsten arc‐welding (GTAW) torch and examined. In the results, it is shown that TiC and B4C increased mechanical properties up to 2 GPa cm3 g−1, with the highest increase observed in heat‐treated B4C samples, achieving specific stiffnesses of 34.6 GPa cm3 g−1 (Ti–6Al–4V) and 32.3 GPa cm3 g−1 (Ti–8Al–1Mo–1V). Powder hot extrusion proves effective in producing Ti–MMCs with high stiffness even with reactive ceramic additions. However, GTAW remelting leads to the decomposition of TiC‐reinforced Ti–MMCs, significantly altering morphology and reducing stiffness below that of the base alloy.

Structure and Phase Composition of (TiB)–Ti Metal Matrix Composites Obtained by SHS and Vacuum Sintering

The structure and phase composition of (TiB)–Ti powder metal matrix composites synthesized by wave combustion with subsequent vacuum sintering are studied. The selected ratio of the reacting components correspond to the presence of unreacted titanium in the combustion products. The behavior of the SHS composite powders synthesized by vacuum sintering is estimated. An analysis of the volumetric and structural changes in the synthesized powder compacts demonstrates that at sintering temperatures of 1300–1350°С, no significant structure transformation occurs, and a slight decrease in the compact volume and the residual pore content is observed. A qualitative phase composition is maintained regardless of the amount of excess titanium and the selected temperature of sintering of the metal matrix composite. The vacuum sintering condition facilitates the redistribution of proportions of phases formed in a nonequilibrium state during synthesis. After sintering, the titanium diboride phase content decreases in favor of a more stable titanium monoboride.

Структура и фазовый состав металломатричных композитов (TiB) - Ti, полученных в процессе СВС и вакуумного спекания

Структура и фазовый состав металломатричных композитов (TiB) - Ti, полученных в процессе СВС и вакуумного спекания

Nano-sized TiN-reinforced composites: Fabrication, microstructure, and mechanical properties

Abstract

Effect of Si, Al2O3, and aluminum dross on sinterability and properties of Ni–Ti metal matrix composites prepared by powder metallurgy

In the present work, composites containing Ni–Ti as a matrix and Si, Al2O3 and alumium dross (mix of Al and Al2O3) as reinforcements were prepared by powder metallurgy technique. The designed mixes were sintered in a low rate argon atmosphere (i.e. with the possiblity for the presence of air) at 1050, 1100 and 1200 °C. The phase indentification of sintered composites was conducted by x-ray diffraction technique. Bulk density and apparent porosity were determined by liquid displacement method according to Archimedes principle. Microstructure of solidified composites was examined by scanning electron microscopy. The hardness of sintered composites was also tested by Vicker indentor. The results revealed that new in situ formed phase as TiO2 was detected in the sintered composites due to the oxidation of Ti. Generally, the sintered composites composed mainly of metal, alloy and oxides as the main components. Furthermore, the apperent porosity was decreased with increasing sintering temperture and with the addition of reinforcments. The composite that contains 20% aluminum dross showed the minimum porosity. The hardness was also improved with increasing the sintering temperture and after addition of reinforcements (Si, Al2O3 and aluminum dross). The composites containing 10 and 20 wt% aluimum dross exhibited the maximum hardness values i.e. 4881 and 4928 MPa, respectively.

Effect of C and Al Elements on High Specific Resistance and High Rigidity of Ultra-High Strength TiC<sub>(1−<i>X</i>)</sub>/Ti Metal Matrix Composites Fabricated by Blended Elemental Reactive Sintering

Effect of C and Al Elements on High Specific Resistance and High Rigidity of Ultra-High Strength TiC<sub>(1−<i>X</i>)</sub>/Ti Metal Matrix Composites Fabricated by Blended Elemental Reactive Sintering

Activating Trace Fe Impurity as Catalyst to Plant Carbon Nanotubes Within Ti-6Al-4V Powders for High-Performance Ti Metal Matrix Composites

External catalysts are commonly pre-coated on Ti alloy powders for in situ synthesis of carbon nanotubes (CNTs) to resolve the inhomogeneity issue, but their excessive introduction changes the matrix composition. Here, we activated the catalytic function of trace Fe impurity solid solute in Ti-6Al-4V powders to plant CNTs within the Ti-6Al-4V powders without modifying the composition. These CNTs exhibited high reactivity with Ti, were retained in the consolidated composites, and improved the mechanical properties.

Interdependencies between graphitization of carbon nanotubes and strengthening mechanisms in titanium matrix composites

Titanium (Ti) metal matrix composites (TMCs) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated by powder metallurgy. Different concentrations (0.5 and 1.0 wt.%) of MWCNTs were dispersed into Ti powder by high energy ball milling (HEBM) and solution ball milling (SBM) processes. The solid-state interfacial reactions between dispersed MWCNTs and Ti matrices were controlled through altering the ball milling parameters and conditions. The powder mixtures were consolidated and sintered at 1100 °C in a vacuum furnace. The graphitization of MWCNTs and its strengthening efficiency in the fabricated TMCs were quantitatively characterized. The relationships between the graphitization and the key strengthening mechanisms were determined. The Ti-0.5 wt.% MWCNTs composites with in-situ TiC nanorods during HEBM and debundling of MWCNTs during SBM processes exhibited compressive yield strength of 882 and 920 MPA which demonstrated 18 and 32% increase compared to commercially pure titanium (CP-Ti), respectively. The key strengthening mechanisms included grain refinement, dispersion strengthening of homogenously dispersed MWCNTs and in-situ TiC particles, solid solution strengthening of carbon, oxygen and nitrogen in Ti matrix, and load-bearing strengthening in TMCs.

Improving the strengthening efficiency of carbon nanotubes in titanium metal matrix composites

Titanium (Ti) metal matrix composites (TMCs) reinforced with multi-walled carbon nanotubes (MWCNTs) were prepared by spark plasma sintering (SPS). Different concentrations (0.5wt% and 1.0wt%) of MWCNTs were dispersed into the Ti matrix by high energy ball milling (HEBM) and solution ball milling (SBM). The impact energy provided to the powder mixtures during the dispersion processing was quantified and optimized to disperse MWCNTs into Ti matrix. The effect of dispersion processing parameters on the sp2 C-C network in MWCNTs, resultant microstructures and mechanical properties of TMCs was investigated. The interfacial reactions between MWCNTs and Ti matrix were controlled by retaining the crystallinity of MWCNTs during the processing stages of TMCs. The defects originated in MWCNTs during the synthesis of TMCs were quantified and their relationship was established with the strengthening efficiency of the MWCNTs in TMCs. The strengthening efficiency of MWCNTs in the composites consolidated from the powder mixtures with pre-sonicated MWCNTs were significantly enhanced as opposed to the composites consolidated from the powder mixtures prepared via solely HEBM process.

Microstructure and mechanical properties of carbon nanotubes reinforced titanium matrix composites fabricated via spark plasma sintering

The influence of various dispersion methods on the evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via spark plasma sintering (SPS) have been investigated. The synthesis procedures included sonication, high energy ball milling (HEBM), and rapid consolidation of powder mixtures at different sintering temperatures. The impact energy provided to the powder mixtures during HEBM process was optimized to disperse 0.5wt% MWCNTs into Ti matrix in two controlled ball milling processes: with and without in-situ formation of TiC during HEBM. The interfacial reactions between MWCNTs and Ti matrix were controlled by retaining the crystallinity and sp2 carbon network of the MWCNTs even at high sintering temperature of 800°C, which enhanced their compressive strength up to 1056MPa with a compressive strain of 27.31%. The mechanical and tribological properties of the composites consolidated from the powder mixtures with in-situ TiC formation during HEBM and pre-sonicated MWCNTs were significantly enhanced as opposed to the composites consolidated from the powder mixtures without formation of TiC during HEBM.

Identifying and understanding the effect of milling energy on the synthesis of carbon nanotubes reinforced titanium metal matrix composites

The influence of milling energy on the dispersion and evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via powder metallurgy has been investigated. High energy ball milling (HEBM) was employed to disperse MWCNTs (0.5 wt.%) into Ti matrix in two controlled ball milling processes: with and without in-situ formation of titanium carbide (TiC). Both types of the powder mixtures were then pressed under 40 MPa into green compacts and sintered in a high vacuum furnace at 1100 °C for 2 h. The evolution of MWCNTs during the fabrication process and the mechanical properties of the sintered composites were discussed in conjunction with the in-situ formation of nano-crystalline TiC. The mechanical properties of the composites consolidated from the powder mixtures with in-situ formed TiC during HEBM were significantly enhanced as opposed to composites consolidated from the powder mixtures without formation of TiC during HEBM.

Effect of dispersion method on the deterioration, interfacial interactions and re-agglomeration of carbon nanotubes in titanium metal matrix composites

The influence of various synthesis techniques on the dispersion and evolution of multi-walled carbon nanotubes (MWCNTs) in titanium (Ti) metal matrix composites (TMCs) prepared via powder metallurgy routes has been investigated. The synthesis techniques included sonication, high energy ball milling (HEBM), cold compaction, high temperature vacuum sintering and spark plasma sintering (SPS). Powder mixtures of Ti and MWCNTs (0.5 wt.%) were processed by HEBM in two batches: (i) ball milling of the mixtures (Batch 1) and (ii) ball milling of Ti powder alone, followed by a further ball milling with sonicated MWCNTs (Batch 2). Both batches of the powder mixtures were pressed at 40 MPa into green compacts and then sintered in vacuum. Batch 2 powder mixtures were also consolidated using SPS. The crystallinity and sp2 carbon network of the MWCNTs were characterized through analyzing the characteristic Raman peak ratio (ID/IG) of each processed sample. X-ray diffraction (XRD) was used for phase identification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of the MWCNTs in the powder mixtures. The evolution of MWCNTs during the fabrication process and mechanical properties of the sintered compacts were discussed in conjunction with the formation of nano-crystalline TiC.

Microstructure of Discontinuously B4C Reinforced Ti Metal Matrix Composites Processed by Hot-Pressing.

Microstructure of Discontinuously B4C Reinforced Ti Metal Matrix Composites Processed by Hot-Pressing.

Ti-SrO metal matrix composites for bone implant materials.

Titanium-strontia (Ti-SrO) metal matrix composites (MMCs) with 0, 1, 3 and 5% (weight ratio) of SrO have been fabricated through the powder metallurgy method. Increasing the weight ratio of SrO from 0 to 5%, the compressive strength of Ti-SrO MMCs increased from 982 MPa to 1753 MPa, while the ultimate strain decreased from 0.28 to 0.05. The elastic moduli of Ti-3SrO and Ti-5SrO MMCs were higher than those of Ti and Ti-1SrO MMC samples. Additionally, the micro hardness of Ti-SrO MMCs was enhanced from 59% to 190% with the addition of SrO. The enhanced compression strength and micro hardness of Ti-SrO MMCs were attributed to the Hall-Petch effect and the SrO dispersion strengthening in the Ti matrix. MTS assay results demonstrated that Ti-SrO MMCs with 3% SrO exhibited enhanced proliferation of osteoblast-like cells. Alkaline phosphatase activity of cells was not influenced significantly on the surface of Ti-SrO MMCs compared with pure Ti in a term longer than 10 days. The cell morphology on the Ti-SrO MMCs was observed using confocal microscopy and scanning electron microscopy, which confirmed that the Ti-3%SrO MMCs showed optimal in vitro biocompatibility.

Influence of Carbon Reinforcements on the Mechanical Properties of Ti Composites via Powder Metallurgy and Hot Extrusion

Ti metal matrix composites (Ti–MMCs) reinforced by vapor grown carbon nanofiber (VGCF) and graphite particle (Gr) were prepared via powder metallurgy and hot extrusion. Ti with 0~0.4wt% VGCF/Gr mixture powders were consolidated by using spark plasma sintering (SPS) at 800 °C. Hot extrusion was then performed at 1000 °C with an extrusion ratio of 37:1. Microstructures and mechanical properties of the as-extruded Ti composites were investigated. Tensile strength of Ti–VGCF/Gr composites was steadily augmented when additions of VGCF/Gr were increased from 0.1 to 0.4 wt%. YS and UTS were increased 40.2% and 11.4% for Ti–0.4wt%VGCF as compared to pure Ti, while those values were 30.5% and 2.1% for Ti–0.4wt%Gr. The strengthening mechanism including grain refinement, carbon solid solution strengthening and dispersion hardening of TiC/carbon was discussed in detail.

Powder metallurgy titanium metal matrix composites reinforced with carbon nanotubes and graphite

Carbon nanotubes (VGCF) and graphite (Gr) reinforced Ti metal matrix composites (TiMMCs) were prepared via powder metallurgy. 0–0.4wt% VGCF/Gr and Ti mixture powders were prepared by rocking mill. The as-premixed powders were consolidated at 1073K using spark plasma sintering (SPS). Hot extrusion was performed at 1273K with an extrusion ratio of 37:1. Microstructures and mechanical properties of the as-extruded Ti composites were investigated to evaluate strengthening effects of VGCF/Gr on Ti matrix. Mechanical strength of Ti–VGCF/Gr composites was augmented when VGCF/Gr contents were increased from 0.1 to 0.4wt%. Yield strength (YS) and ultimate tensile strength (UTS) of Ti-0.4wt% VGCF composites were increased 40.4% and 11.4% as compared to pure Ti, while those values were 30.5% and 2.1% for Ti–0.4wt% Gr. The strengthening mechanism including grain refinement, carbon solid solution strengthening and TiC/carbon dispersion strengthening was discussed in detail.

Microstructures and mechanical properties of the in situ TiB–Ti metal–matrix composites synthesized by spark plasma sintering process

In situ synthesized TiB reinforced titanium matrix composites have been synthesized by spark plasma sintering (SPS) process at 950–1250 °C, using mixtures of 15 wt% TiB 2 and 85 wt% Ti powders. The effects of the sintering temperature on densification behavior and mechanical properties of the TiB–Ti composites were investigated. The results indicated that with rising sintering temperatures, relative densities of the composites increase obviously, while the in situ TiB whiskers grow rapidly. As a result, bending strength of the TiB–Ti composites increases slowly at the combined actions of the factors referred above. Fracture toughness of the composites is improved remarkably due to the large volume fraction of Ti matrix, the crack deflection, pull-out and the micro-fracture of the needle-shaped TiB grains. The results also suggested that TiB–Ti composite sintered at 1250 °C by SPS process exhibits the highest relative density of 99.6% along with bending strength of 1161 MPa and fracture toughness of 13.5 MPa m 1/2.

The effects of interfacial debonding on the elastoplastic response of unidirectional silicon carbide—titanium composites

A three-dimensional micromechanics-based analytical model is presented to investigate the effects of initiation and propagation of interface damage on the elastoplastic behaviour of unidirectional SiC—Ti metal matrix composites (MMCs) subjected to off-axis loading. Temperature-dependent properties are considered for the matrix. Manufacturing process thermal residual stress (RS) is also included in the model. The selected representative volume element consists of r× c unit cells in which a quarter of the fibre is surrounded by matrix sub-cells. The constant compliance interface model is used to model interfacial debonding and the successive approximation method together with von Mises yield criterion is used to obtain elastoplastic behaviour. Dominance mode of damage including fibre fracture, interfacial debonding, and matrix yielding and ultimate tensile strength of the SiC—Ti MMC are predicted for various loading directions. The effects of thermal RS and fibre volume fraction on the stress—strain response of the SiC—Ti MMC are studied. Results revealed that for more realistic predictions, both interface damage and thermal RS effects should be considered in the analysis. The contribution of interfacial debonding and thermal RS in the overall behaviour of the material is also investigated. Comparison between results of the presented model shows very good agreement with the finite-element micromechanical analysis and experiment for various off-axis angles.

Effect of starting powder grade on sintering and properties of PM titanium metal matrix composites

The attractive physical and mechanical properties that can be obtained with Ti metal matrix composites (Ti-MMCs), such as high specific modulus, strength or wear resistance have been documented extensively. Interest in MMCs for use in the automotive industries, aerospace, and other structural applications has increased over the past 25 years as a result of several processing routes being developed and availability of reinforcements. Additionally, Ti powder metallurgy offers the possibility of creating net shape or near net shape parts without the material loss and cost associated with machining intricate components from wrought stock material, Ti being notoriously difficult to machine. This work focuses on research of a suitable Ti based metal matrix which will be reinforced by particles. First an adequate sintering assembly was designed and studied. Next, in order to achieve desired levels of mechanical properties, different Ti powders (either pure Ti or Ti hydride) were tested as metal matrix. These compacts were handled in different atmospheres (Ar and air) and compacted at different pressures followed by sintering at different conditions (temperature, time). Characterisation of the samples included hardness, density, oxygen content and microstructural analysis. This showed the influence of impurities in the raw powder as well as of the powder size and the processing parameters. Finally after the characterisation results, the two most suitable starting powders were selected for the fabrication of the Ti-MMCs. Such Ti based matrices have been reinforced with particles (TiB2) at varying contents. Conclusively, the characterisation results of the compacted Ti based composites showed the importance of the adequate selection of the starting powder and the processing parameters simultaneously to achieve the desirable levels of mechanical properties for the Ti based composites.

Small Punch Test of Advanced <i>In Situ </i>Synthesized Ti Metal Matrix Composites

Particulate reinforced 10 vol.% (TiB+TiC)/Ti-6Al-4V metal matrix composites (MMCs) were produced by in-situ synthesis using vacuum arc re-melting process, and the mechanical properties of the metal matrix composites were assessed by the small punch testing (SPT). Mechanical properties of the in-situ synthesized Ti MMCs were studied and compared with the Ti base alloy. From the test data, the fracture properties and equivalent fracture strain of the test materials were characterised. The fracture mechanism of the test samples was examined using scanning electron microscopy.