Ti B4C System Research Articles

Accelerated Diffusion Phenomenon in Ti-B4C System and its Influence on the Resulting Composites

Accelerated Diffusion Phenomenon in Ti-B4C System and its Influence on the Resulting Composites

Interface formation and bonding control in high-volume-fraction (TiC+TiB2)/Al composites and their roles in enhancing properties

As interfaces play a more important role in high-volume-fraction ceramic/metal composites because of containing more hetero-phase interfaces, it is a great challenge to control the interfaces in such composites to balance their strength and plasticity and to obtain high performances. In this work, 50–60 vol% (TiC + TiB2)/Al composites were fabricated in Al–Ti–B4C system via a one-step method of reaction and densification, and their interface bonding and mechanical properties were compared with those of in-situ TiC/Al composites. Apparently, the defects, such as interfacial discontinuity, macro-pores, coarsening and agglomeration of particles, caused by increased ceramic content in the TiC/Al composites, are eliminated in the (TiC + TiB2)/Al composites using Al–Ti–B4C system. The 60 vol% (TiC + TiB2)/Al composite exhibits significantly enhanced mechanical properties, i.e. 70.5%, 60.7% and 69.8% respectively higher yield strength, ultimate compressive strength and plastic strain than 60 vol% TiC/Al composite. Such enhanced mechanical properties are attributed to the improvement in interface bonding strength and therefore the increase in the energy dissipation of crack propagation. The formation of enhanced interface in the (TiC + TiB2)/Al composites results from the reduction in the reaction heat in the Al–Ti–B4C system, improved crystallographic match and improved adhesion work between ceramic particles and matrix. This work may provide a new idea for the design and control of interfaces in high-volume-fraction ceramic-metal composites.

Development of in situ composites via reactive friction stir processing of Ti–B4C system

In situ titanium matrix composites were fabricated by introducing an exothermic reaction between Ti and B4C during friction stir processing (FSP). Formation of TiB, TiB2, and TiC was confirmed by X-ray diffraction and transmission electron microscopy along with energy dispersive X-ray spectroscopy and diffraction pattern. TiB and TiB2 whiskers and TiC particles influenced the dynamic recrystallization process, which facilitated an equiaxed grained structure rather than the Widmanstätten microstructure. Mechanical properties of as-received Ti–6Al–4V including hardness, elastic modulus, compressive yield strength and work-hardening rate (stage B) were improved by ∼ 57%, 17%, 47% and 100%, respectively, after FSP with B4C.

Microstructure evolution and its effect on mechanical response of the multi-phase reinforced Ti-based composites by laser powder-bed fusion

The Ti-based composites reinforced by in-situ formed TiB and TiC particles were successfully produced by laser powder-bed fusion (LPBF) additive manufactured technology using a B4C/Ti composite powder mixture, in order to further enhance the mechanical properties of commercially pure titanium (CP-Ti). The effects of applied laser energy density on the microstructure and attendant mechanical properties of the LPBF-processed parts were investigated, and meanwhile, the underlying formation mechanisms of the TiB and TiC particles by LPBF were elucidated. It showed that the whisker-like TiB and near-granular TiC reinforcements were in-situ formed through a laser-induced reaction of Ti-B4C system via a diffusion-nucleation-growth mechanism from the melt. The in-situ reinforcements arranged from dendrite to cellular morphology were primarily determined by the thermal convections that transformed from dendrite to annular patterns as a result of the great elevation of temperature gradient between molten Ti liquid and heated B4C particles as an increase in the applied laser energy density. The tensile tests revealed that the LPBF-ed Ti-based composites possessed an enhanced tensile strength from 893 ± 5 MPa to 1211 ± 8 MPa and a slightly reduced elongation from 18.1% to 16.8% with the transition of typically fracture morphologies from elongated dimples to equiaxed-ultrafine dimples, respectively, attributed to the combined grain refinement and microstructure strengthening effects.

Structure formation and densification of TiB2-TiC-Ni composites produced by chemical reaction of Ti-B4C system in high-gravity field

TiB2-TiC-Ni composites were achieved through direct reaction of Ti and B4C powder blends in a high gravity field of 1800 g with Ni binder. The microstructure of TiB2-TiC composites present pore-free with darker TiB2 platelets and the brighter TiC equiaxed grains easily distinguishable. Ti-B-C-Ni full-liquid SHS intermediate products immediately were formed following the reaction of Ti and B4C, which was considered to yield inherently fine-grained microstructures under the rapid cooling condition. The role of high gravity field was proposed as promoter of the final products densification and grain refinement of TiB2-TiC composites.

Effects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of in situ 50 vol.-% (TiB2–TiCx)/Al–Cu composites

ABSTRACTEffects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of 50 vol.-% (TiB2–TiCx)/Al–Cu composites fabricated via the combustion synthesis (CS) method assisted with hot press from the Al–Ti–B4C system were studied. With decrease in the TiB2/TiCx ratio from 3:1 to 1:3, the shape of TiB2 changed from platelike to clubbed while the size of TiCx particles increased, which directly led to different mechanical properties. The 50 vol.-% (TiB2–TiCx)/Al–Cu composite with the TiB2/TiCx ratio of 2:1 exhibited good compression strength without sacrificing the fracture strain, while the composite possessed the highest abrasive wear resistance when the TiB2/TiCx ratio was 3:1. The appropriate TiB2/TiCx ratio was recommended to be 2:1 in this research.

Microstructure and properties of in-situ TiB2 matrix composite coatings prepared by plasma spraying

TiB2-TiC and Ti-B4C composite powders were plasma sprayed onto the 45 steel substrates, respectively, for preparing TiB2 matrix composite coatings. The microstructure and properties of as-prepared coatings were investigated comparatively. The coating prepared by plasma spraying TiB2-TiC composite powder showed the characteristics of stacking of partially melted or unmelted feedstock particles, loose microstructure, high porosity, and poor property. For Ti-B4C system, the main phase TiB2 and TiC0.3N0.7 were formed due to the reaction between Ti and B4C during the plasma spraying process. The as-prepared coating displayed dense microstructure and better quality. The properties of the coating prepared by plasma spraying Ti-B4C composite powder were much better than that of the coating prepared by TiB2-TiC composite powder.

Microstructural evolution and competitive reaction behavior of Ti-B4C system under solid-state sintering

By using experimental investigations and theoretical calculations, microstructural evolution and competitive reaction behavior of Ti-B4C system under solid-state sintering is confirmed. Firstly, B4C decomposes into B and C atoms followed by diffusing into Ti side immediately, and TiB whiskers form in Ti matrix. Then, Ti atoms diffuse into B4C via vacancies left by the diffused B and C atoms, leading TiB2 and carbon substance to form in B4C side. Subsequently, reaction product carbon diffuses into Ti side and concentration of C in Ti side increases accordingly, resulting in the formation of TiC particles in Ti matrix. With further processing of reaction, both amount and size of products increases gradually. When TiB2 phases grow into a monolithic layer, diffusion behavior between Ti and B4C is inhabited, carbon presents to be a loose layer between un-reacted B4C and TiB2, and the in situ reaction also stops finally.

Grain Refining Efficiency of SHS Al–Ti–B–C Master Alloy for Pure Aluminum and Its Effect on Mechanical Properties

A new Al–5Ti–0.75B–0.2C master alloy was successfully prepared by self-propagating high-temperature (SHS) reaction from an Al–Ti–B4C system with molten Al. Microstructure and phase characterization of the prepared Al–5Ti–0.75B–0.2C master alloy show that the nearly spherical TiC particles, hexagonal or rectangular TiB2 particles, and block-like TiAl3 particles distribute uniformly in the aluminum matrix. Grain refining test on commercial pure aluminum indicates that Al–5Ti–0.75B–0.2C master alloy exhibits a better grain refining performance than Al–5Ti–1B master alloy. By addition of 0.2 wt% Al–5Ti–0.75B–0.2C master alloy, the average grain size of α-Al can be effectively refined to 160 ± 5 μm from about 3000 μm, and the tensile strength and elongation are increased by about 20% and 14.1% due to the grain refinement.

In situ fabrication of TiC–TiB2 precipitates in Mn-steel using thermal explosion (TE) casting

Abstract

Microstructure and mechanical properties of P/M titanium matrix composites reinforced by in-situ synthesized TiC–TiB

Titanium matrix composites (TMCs) were prepared via reactive Ti-B4C system by powder metallurgy and hot extrusion route. The effect of the volume fraction of in-situ synthesized TiC particles and TiB whiskers on microstructure and mechanical behavior of TMCs were investigated. TiB whiskers showed favorable alignment oriented parallel to the deformation axis after hot extrusion; TiC particles and TiB whiskers distributed homogenously throughout the as-extruded composites. σUTS of the synthesized TMCs increased gradually from 654MPa to 1138MPa when the volume fractions of hybrid TiC and TiB were raised from zero to theoretical value of 13.6vol%; the elongation decreased from 32.4% to 2.6% correspondingly. The strengthening effect of in-situ formed TiC–TiB hybrid reinforcements at room and elevated temperature was studied based on the load-transfer mechanism between the titanium matrix and TiC–TiB reinforcements. It was found that synergistic of the TiC particle and TiB whisker showed beneficial strengthening effect on mechanical properties of TMCs.

Pinning Effect of In-Situ TiC<sub>p</sub> and TiB<sub>w</sub> on the Grain Size and Room Temperature Strength of (TiC + TiB)/Ti Composites

(TiCp + T iBw)/Ti composite was firstly prepared by spark plasma sintering (SPS) and hot extrusion from Ti-B 4C system, and then isothermally heat treated at 400–800 ° C for 24 h to study the pinning effect of the in situ formed reinforcements. Microstructure and phase composition was investigated by SEM, XRD and TEM, variation of the grain size of Ti matrix was studied by EBSD analysis, and room temperature strength was also measured after different heat treatments. Results show that, comparing with pure Ti materials, both the grain size of Ti matrix and the room temperature strength of the composite almost keep stable after heat treatments, suggesting the pinning effect of in situ formed TiCp and TiBw is effective to suppress the growth of Ti matrix grains during heat treatments.

Size effect of B4C powders on metallurgical reaction and resulting tensile properties of Ti matrix composites by in-situ reaction from Ti–B4C system under a relatively low temperature

Ti matrix composites (TMCs) were prepared by using spark plasma sintering (SPS) and hot extrusion from Ti–B4C powder system with different sizes of B4C addition. Tensile properties, O/N contents, grain sizes, microstructures, phase compositions and fractured surfaces were investigated systematically. Then, the effect of B4C particle size on the strength and ductility of TMCs were discussed based on the experimental results and strengthening theory. Results showed that coarse B4C powders led to incomplete reaction and decrease of the amount of both TiCp and TiBw in the Ti matrix, thus resulting in the significant decrease of strength but increase of elongation. The strength improvement of TMCs could be mainly attributed to the strengthening effect of in-situ formed TiCp and TiBw, especially the load-bearing transformation of TiBw. However, the limitation of the TiBw on the deformation of Ti matrix decreased the ductility of the TMCs dramatically.

Stability of strengthening effect of in situ formed TiCp and TiBw on the elevated temperature strength of (TiCp + TiBw)/Ti composites

(TiCp+TiBw)/Ti composite was firstly prepared by spark plasma sintering (SPS) and hot extrusion from Ti–B4C system, and then isothermally heat treated at 400–700°C for 24h, respectively. The elevated temperature tensile strength was tested at temperatures corresponding to isothermal heat treatments. Microstructure characterizations were carried out by using SEM, EPMA, XRD, EBSD and TEM. Results show that, the microstructure of (TiCp+TiBw)/Ti composite consists of Ti matrix, particle-like TiC and whisker-like TiB. TiCp and TiBw are stable at elevated temperatures and can prevent Ti matrix from coarsening. On the other hand, the strength of the composite decreases significantly with the increase of testing temperature, but it is always in proportion to that of pure Ti tested at the same temperature, indicating the strengthening effect of in situ formed TiCp and TiBw is stable at elevated temperature. The decrease of elevated temperature strength of (TiCp+TiBw)/Ti composite can be mainly attributed to the high temperature softening of Ti matrix.

Effect of B4C particle size on the reaction behavior of self-propagation high-temperature synthesis of TiC–TiB2 ceramic/Cu composites from a Cu–Ti–B4C system

The effect of B4C particle size on the reaction behavior of TiC–TiB2 ceramic/Cu composites from a 40wt.% Cu–Ti–B4C system by self-propagation high-temperature synthesis (SHS) was investigated. It was found that increasing B4C particle size not only makes the ignition and self-sustainment of the SHS reaction difficult but also decreases the combustion temperature and combustion wave velocity. The reaction products are dependent on the B4C particle size. Favorable composites consisting of TiC, TiB2 and Cu phases could be obtained by the control of B4C particle size. The reaction path was explored through a delicate microstructure and phase analysis on the combustion-wave quenching method. From the reaction path, the effect of B4C particle size on the ignition behavior, combustion characteristics and products of the Cu–Ti–B4C system can be clearly clarified.

Fabrication of bionic composite material using self-propagating high-temperature synthesis in the Cu–Ti–B4C system during steel casting

Enlightened by the nacreous layer of shell, this study successfully fabricated the bionic composite material using self-propagating high-temperature synthesis (SHS) reaction in the 40 wt.% Cu–Ti–B4C system during manganese steel casting. The phase constituents, microstructures and wear resistance of the bionic composite material were investigated. The results show that bionic composite material was alternant combination of manganese steel matrix and unit region in a relatively large dimension. Excellent metallurgy bonding between the unit region and steel matrix in the bionic composite material was presented. The results analyzed with X-ray diffraction (XRD) reveal the existence of TiC, TiB2, Cu and austenite without any intermediate phases in the unit region. Due to sufficient infiltration of the melted steel, the unit region had the fewest macro-pores and blowholes. This indicates that the near fully dense bionic composite material can be fabricated. The wear tests show that the wear resistance of the bionic composite material fabricated was better than that of the pure manganese steel.

Mechanism in reactive plasma spraying synthesis of TiC–TiB2 composite coating

Self-propagating high-temperature synthesis reaction in the LaMgAl11O19–Ti–B4C system was quenched in the glove box and during plasma spraying, respectively, in order to clarify the formation mechanism of in situ TiC–TiB2 composite coating. Microstructure of the quenched samples was investigated by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometer. The results showed that the formation mechanism of TiC and TiB2 during reactive plasma spraying is same as that in the glove box, namely the Ti–B–C melt is first formed by B4C particles dissolving into the Ti–B eutectic liquid as well as the molten Ti, and then TiC and TiB2 are formed and precipitated from the saturated Ti–B–C melt.

Self-propagating high-temperature synthesis of TiC–TiB2-based Co cermets from a Co–Ti–B4C system and fabrication of coatings using the cermet powders

TiC–TiB2-based Co cermets with various Co contents were successfully synthesized by self-propagating high-temperature synthesis (SHS) from a Co–Ti–B4C system. Effects of Co content and particle size of Ti and B4C powders on the SHS reaction were investigated. It was found that with an increase in Co content, the ignition delay time first decreased and then increased. The SHS products consisted of the desired phases of TiC, TiB2 and Co regardless of the Co content. The particle size of Ti and B4C powders had negligible effects on the combustion temperature and SHS products to some extent. However, the ignition of SHS reaction was significantly dependent on the Ti and B4C powders, especially on the B4C powders. The formation mechanism of TiC and TiB2 during SHS was proposed based on the combustion-wave quenching experiment. Moreover, the TiC–TiB2-based Co cermet coatings were fabricated by atmospheric plasma spraying using the SHS-derived powders, which could provide better wear resistance for the alloy substrates such as steel.

Compression properties and abrasive wear behavior of high volume fraction TiCx–TiB2/Cu composites fabricated by combustion synthesis and hot press consolidation

The 40–60vol.% TiCx–TiB2/Cu composites were successfully fabricated by the combustion synthesis and hot press consolidation in a Cu–Ti–B4C system. The final products consist of only Cu, TiCx and TiB2, and the ceramic particles distribute uniformly in the composites. The sizes of the ceramic particles decrease with the increasing Cu content. The yield strength, ultimate compression strength and microhardness increase with the increasing TiCx–TiB2 content. The incorporation of the TiCx–TiB2 particles improves the wear resistance of the composites effectively, and the wear resistance increase with the increase in the TiCx–TiB2 content.

Effect of Cu content in Cu–Ti–B4C system on fabricating TiC/TiB2 particulates locally reinforced steel matrix composites

The austenite manganese steel–matrix composites locally reinforced with in situ TiC/TiB2 particulates were successfully fabricated using self-propagating high-temperature synthesis (SHS) reactions in a Cu–Ti–B4C system and the effect of the Cu content during casting has been investigated. The local reinforcing regions in the steel matrix composites mainly consist of TiC, TiB2, Cu and austenite, without any intermediate phases. With the increase in the Cu content, the size of the ceramic particulates in the local reinforcing regions decreases, the interface bonding between reinforcing region and matrix becomes poor and the macro-pores and blowholes in the local reinforcing regions become fewer. Moreover, with the increase in the Cu content, the hardness value decreases monotonically, while the wear resistance of the reinforced region increases first then decreases.