TiB2 Nanoparticles Research Articles

Precipitation Hardening and Corrosion Behavior of Friction Stir Welded A6005-TiB2 Nanocomposite

Precipitation hardening and corrosion behavior of a friction stir welding (FSW) based on the aluminum alloy A6005 reinforced with TiB2 nanoparticles have been studied. Mechanical alloying (MA) and hot extrusion techniques have been employed as processing route followed by FSW. Samples characterization has been performed by DSC and TEM, and precipitation strengthening of the bulk samples and the FSW joint has been evaluated by micro-hardness tests after T6 thermal treatment. TEM characterization revealed the presence of Mg–Si hardening phases, mainly of β′ phase, and dispersoids of α-Al(FeMnCr)Si into the aluminum matrix. The results revealed that samples subjected to MA had less susceptibility to T6 thermal treatment and that the presence of nano-TiB2 reinforcement accelerates aging time. In addition, electrochemical tests based on polarization tests have been performed in 3.5% NaCl solution to assess the effect of FSW process on corrosion behavior. The FSW joint had worse corrosion behavior since the passive Al2O3 film was not generated on the weld zone. SEM–EDS analysis revealed that pits nucleated mainly in sites with a higher presence of Fe contaminant which acts cathodically with respect to the aluminum matrix, producing galvanic corrosion.

The effect of in-situ formed TiB2 particles on microstructural and mechanical properties of laser melted copper alloy

Abstract Mixed Cu-4Ti (wt.%) and Cu-1.4B (wt.%) powders were separately mechanically alloyed and then homogenized. The obtained powder was laser melted by pulsed Nd:YAG laser and heat treated at 900 °C for 10 h in argon. 3D compacts were characterized by means of digital camera images, optical microscopy and scanning electron microscopy. Microstructure after laser melting varies regionally due to mixing of two different mechanically alloyed powders and contains in-situ formed microparticles of primary TiB2. Formation of secondary TiB2 nanoparticles was possible only after high temperature heat treatment (900 °C, for 10 h) as concluded from X-ray diffraction analysis, chemical analysis, and microhardness tests of laser melted and heat treated parts. Copper matrix was strengthened to a significantly higher extent after the formation of secondary TiB2 nanoparticles.

Effect of electron concentration on electrical conductivity in in situ Al-TiB2 nanocomposites

Electrical conductivity is important for the applications of metals containing nanoparticles, and a thorough understanding of how nanoparticles affect their electrical conductivity is much needed. In this paper, an in situ Al-TiB2 nanocomposite is used as a model system to study its electrical behavior from 10–300 K with Hall scanning up to ±6 T. By experimentally identifying the respective contributions from the nanoparticle size, grain boundaries, dislocation density, and nanoparticle volume percentage, it suggests that a low volume percent of TiB2 nanoparticles can reduce the electron concentration significantly to decrease the electrical conductivity of the Al-TiB2 nanocomposites, while yielding less effect on the electron mobility. Moreover, the results show that the intrinsically enhanced electron-phonon interaction and the interfacial bound states by TiB2 nanoparticles play a role in lowering the electron concentration. This understanding of how nanoparticles affect the electrical conductivity provides useful insights into the rational design and optimization of metal matrix nanocomposites for numerous applications.

Fabrication and Characterization of In Situ Zn-TiB2 Nanocomposite

Zinc (Zn) matrix composite has been newly discovered categories of biodegradable materials. With a combination of chemical stability, thermal stability and biocompatibility, ceramic nanoparticles outperformed intermetallics of zinc alloys with inherent advantages of retaining a proper corrosion rate and an exceptional ductility. Compared with Zn alloys, Zn matrix nanocomposites showed an unprecedented strengthening without sacrifices of corrosion rate, which were introduced by intermetallics. In this work, in situ titanium diboride (TiB2) reinforced Zn nanocomposite was prepared via a few cost-effective and economical methods: flux-assisted synthesis (FAS), ultrasound-assisted nanoparticle homogenization and hot rolling. 3 vol.% of TiB2 nanoparticles were synthesized with an average size of 454nm, followed by molten salt assisted ultrasound homogenization and hot rolling. Hot-rolled (HR) Zn-TiB2 performed high strength and high ductility, mostly due to precipitation strengthening (Orowan strengthening). Yield stress (YS) and ultimate tensile stress (UTS) increased by 90% and 45%, respectively, while the elongation to failure retained 23%. The mechanical performance of Zn-TiB2 made it promise to serve as an innovative biodegradable material for load-bearing applications.

The effect of synthesis of the starting powders on the properties of Cu-Ti-TiB2 alloy obtained by laser melting

A comparison was made between layer-by-layer laser melting (LM) of two types of feedstock powders: (1) elemental powder blend and (2) mechanically alloyed powder. LM was done by Nd:YAG laser at 1064 nm (max. average power 100 W) in argon ambience. Samples synthesized were Cu-Ti-TiB2 rectangular tracks (20?6?1 mm), and input parameters of the process: powder layer thickness 100-250 ?m, hatch spacing 1 mm, pulse length 4 ms, energy 4 J, pulse repetition rate 20 Hz. Part of the samples was heat-treated in argon at 900 ?C, 10 h. Structural characterization of the samples was done using light microscope and scanning electron microscope (SEM). Chemical analysis of the as-obtained laser melted samples was done by inductively coupled plasma-atomic emission spectrometry (ICP-AES). It was established that the microstructure of LM samples was comprised of Cu-Ti and Cu-B solid regions, and in situ formed microparticles of primary TiB2. Only after high-temperature thermal treatment has the secondary TiB2 occurred. Tensile tests showed much higher strengthening in heat-treated samples with mechanically alloyed powder as starting material, where the formation of secondary TiB2 nanoparticles was considerable.

Atomic-scale investigation of the interface precipitation in a TiB2 nanoparticles reinforced Al–Zn–Mg–Cu matrix composite

The effects of nanosized reinforcement particles on precipitation reactions in age-hardenable Al alloy matrix composites have been largely unknown. In this work, an Al–Zn–Mg–Cu matrix composite reinforced with uniformly distributed TiB2 nanoparticles was successfully produced. The solid-soluted, peak-aged and overaged materials were then characterized, at the atomic scale using (high-resolution) scanning transmission electron microscopy, to provide a fundamental insight into the interface precipitation. Our results demonstrated that the facetted TiB2 nanoparticles have a significant impact on the precipitation in matrix areas adjacent to the TiB2/Al interfaces. The interfaces after solid-solution treatment are tightly-bonded and oxide-free. The TiB2 particles and Al matrix display two orientation relationships (ORs): the well-reported [21¯1¯0]TiB2//[101]Al, (0001)TiB2//(1¯11)Al (OR1) and the new [21¯1¯0]TiB2//[101]Al, (011¯0)TiB2//(111¯)Al (OR2). The interface precipitates (i.e., interphase) having the size of several tens of nanometers were formed after ageing and were determined to be (Zn1.5Cu0.5)Mg phase. Their formations were only related to the initial OR1 and OR2 where the mutual ORs between the TiB2, interphase and Al matrix were further developed. Periodically spaced misfit dislocations were revealed at the semi-coherent TiB2/Al interfaces, which are generally considered beneficial to the heterogeneous precipitation. They not only reduced nucleation energy barrier, but also acted as short-circuit diffusion paths for transporting solute atoms and vacancies, accelerating growth rate. However, the growth of interphase at the interface parallel to close-packed {111} Al planes was suppressed by the ultra-low accommodation factor. In addition, such an interface precipitation reduced the mismatch of the TiB2/Al interface, increasing the overall coherency and being potential for effective interface strengthening.

Advanced heat treated die-cast aluminium composites fabricated by TiB2 nanoparticle implantation

The global carbon emission reduction strongly requires high strength lightweight die-cast aluminium alloys in industry. Here die-cast AlSiMgMn–TiB2 composites with advanced mechanical performance were fabricated by the implantation of TiB2 nanoparticles. Super vacuum assisted high pressure die casting was applied to enable the T6 heat treatment of the composites, and the super vacuum of 20 mbar was achieved in the limited evacuation time of 1.6 s. The composites demonstrated good die castability within the addition of 3.5 wt% TiB2, while the composites could not fill into the chill vent with the addition of >3.5 wt% TiB2. The composite with 3.5 wt% TiB2 nanoparticles delivered the high hardness of 150.2 kg/mm2, yield strength of 351 MPa, tensile strength of 410 MPa, and the industrially applicable good ductility of 5.2%, after T6 heat treatment. The strengthening of the T6 heat treated composite was a result of both TiB2 nanoparticles and nanoscale β′′ precipitates that had coherent interfaces with α–Al matrix, i.e., Al(11-1)//TiB2(0001), Al[011]//TiB2[11-20], Al[320]//β″(a-axis), Al[1-30]//β″(c-axis) and Al(020)//β″(b-axis). The T6 heat treated composite reinforced by 3.5 wt% TiB2 showed ductile fracture.

Synthesis of Nano-Sized TiB2 and TiC Particles During Spark Plasma Sintering of Ball-Milled Ti-Cu Alloy + B(C) and Ti+Cu+B mixtures

Ti-B-Cu and Ti-C-Cu systems are interesting from the viewpoint of the development of ceramic particle-reinforced copper matrix composites. In this work, the phase and structural evolution upon the interaction of Ti33Cu67 and Ti25Cu75 alloys obtained by melt spinning with carbon or boron was studied. The reactions were carried out in the ball-milled mixtures subjected to Spark Plasma Sintering at 900 °C. The products of the reactions were composites containing TiC or TiB2 nanoparticles distributed in the copper matrix. The in-situ synthesized TiC and TiB2 nanoparticles were extremely fine (10-20 nm). The distribution pattern of the particles in the matrix was similar in the TiC-Cu and TiB2-Cu systems: composite regions were intermixed with copper regions free from the ceramic particles. It was shown that, when the Ti25Cu75 alloy was melted first by heating up to 900 °C and then forced to interact with carbon, TiC particles two orders of magnitude larger in size grew in the copper matrix.

Wear and thermal stability of nano-TiB2 modified TiCN-WC-Co-Cr3C2 cermet

This work discusses the friction, wear and thermal response of TiCN-WC-Co-Cr3C2 cermet modified by the addition of TiB2 nanoparticles. The specimens were prepared by spark plasma sintering by adding different weight percentages (5, 10 and 15) of TiB2 nanoparticles in TiCN-WC-Co-Cr3C2 cermets. The sintered pieces were subjected to sliding wear under an unlubricated condition and a constant load of 20 N at sliding velocities of 0.23 m/s, 0.35 m/s and 0.47 m/s against a steel disc of 48 mm diameter. Friction was the maximum at a sliding velocity of 0.23 m/s. The wear loss decreased with increasing speed of sliding and was between 10−5 to 10−6 mm3. The wear rates and coefficient of friction were highly dependent on microstructure and mechanical properties of the cermets. Abrasion and adhesion were the active modes of wear. Heating of the samples was carried out at 600 °C, 800 °C and 1000 °C for 4 h. A substantial mass gain and decrease in hardness were observed in the specimen annealed at 1000 °C, for which Scanning Electron Microscopy revealed considerable grain growth and XRD showed oxide phases. A cermet containing 15% TiB2 nanoparticles displayed the lowest volumetric wear at room temperature, but had rather low thermal stability. Response surface methodology was used to develop models and regression equations for wear and thermal stability.

In-situ formation of ultrafine MgNi3B2 and TiB2 nanoparticles: Heterogeneous nucleating and grain coarsening retardant agents for magnesium borate in Li–Mg–B–H reactive hydride composite

Li–Mg–B–H reactive hydride composite (RHC) has attracted extensive attention over the past decades for its extremely high hydrogen storage capacity (11.5 wt%). But the sluggish desorption kinetics for the second step dehydrogenation reaction need to be further improved. Herein, short rod-like TMTiO3 (TM = Co, Ni) bimetallic oxides, which contain two kinds of transition metal elements, were synthesized and introduced into Li–Mg–B–H RHC for the first time. The NiTiO3 exhibits excellent catalytic effect on the hydrogen desorption kinetic performance of Li–Mg–B–H RHC, and the incubation period for the second step dehydrogenation reaction is eliminated completely by reducing the apparent activation energy for the generation of MgB2 from 296 kJ/mol to 269 kJ/mol. The NiTiO3 doped Li–Mg–B–H RHC can desorb about 9.0 wt% H2 without obvious attenuation of kinetic performance in five cycles. Mechanism analyses reveal that the in-situ generated nano-sized MgNi3B2 and TiB2 species (∼5 nm) both meet the critical value ( < 10%) of the edge-to-edge matching model (5.77% for MgNi3B2 and 2.22% for TiB2), which play a significant role in supporting the nucleation of MgB2. Meanwhile, the extremely fine MgNi3B2 and TiB2 heterogeneous nucleation sites can inhibit the excessive growth for a single crystal nucleus of MgB2. The heterogeneous nucleation and grain refinement mechanisms caused by the novel bimetallic oxide could provide alternative insights into designing an in-situ generated nano-sized catalytic hydrogen storage system with enhanced kinetics and cyclic stability for hydrogen-fueled applications.

High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

The structural lightweight in automotive and other industries motivates the usage of high strength die-cast aluminium alloys. However, the improvements of die-cast aluminium alloys are struggling limited by conventional micro alloying, and the improved yield strengths are still in the low level of 180–190 MPa. Here, high performance die-cast AlSiMgCu/TiB2 composite was fabricated through the reinforcement of TiB2 nanoparticles and the latest developed cutting-edge super vacuum assisted high pressure die casting (HPDC) process. The composite with 3.0 wt% TiB2 nanoparticles could deliver the milestone high hardness of 1.56 GPa, yield strength of 356 MPa, tensile strength of 457 MPa and an industrially applicable ductility of 5.5%. The composite was strengthened by TiB2 nanoparticles and nanoscale Q′ and θ′ precipitates that all had highly coherent interfaces with the α–Al matrix, indicative of strong interfacial bonding. The implantation of TiB2 nanoparticles also induced special grain refinement strengthening of the composite. The fabricated composite demonstrates ~90% increase in strength over the currently available alloys, and it is promising for industrial application.

Atomic structure and interface chemistry in a high-stiffness and high-strength Al–Si–Mg/TiB2 nanocomposite

We investigate a new generation of aluminium alloys, Al–Si–Mg/TiB2 nanocomposites, with both high stiffness (Young's modulus 94 GPa) and high yield strength (322 MPa), designed for automotive applications. A significant weight reduction (>30%) can be achieved by these nanocomposites compared with conventional Al alloys in components designed for stiffness. The crystallography and distribution of TiB2 particles and β″ precipitates, as well as the chemistry and structure of Al/TiB2 interfaces, have been characterized at atomic scales. The TiB2 nanoparticles (average particle size ∼450 nm), the main cause of stiffness improvement, were homogeneously distributed within the Al–Si–Mg matrix. The interfaces between Al and TiB2 nanoparticles were mainly parallel to dense planes of the TiB2, including basal {0001}, prismatic {11¯00} and pyramidal {011¯1} planes. All facets show a transitional zone in the alloy matrix, roughly 1 nm in thickness. We also find a Cu-rich layer (∼2 at.%) on pyramidal {011¯1} facets. The β″ precipitates are the main cause of high yield strength and work in conjunction with TiB2 nanoparticles to produce an alloy with outstanding mechanical properties.

Effect of nano-TiB2 particles on the anisotropy in an AlSi10Mg alloy processed by selective laser melting

In components built by selective laser melting (SLM), possible anisotropy in microstructure significantly affects mechanical properties (i.e. service performance) and there is a constant effort to solve this problem. This work carried out a comparative study using fully dense AlSi10Mg alloy and in-situ nano-TiB2 decorated AlSi10Mg composite samples processed by SLM. The aim was at clarifying the effect of integrated nanoparticles on the anisotropy of the as-built component. Microstructure and texture evolution were investigated by scanning and transmission electron microscopy, electron backscatter diffraction, X-ray and neutron diffraction. The SLMed AlSi10Mg sample shows a coarse columnar grain structure with <100> and <110> fiber orientation texture and obvious anisotropy in mechanical properties. However, the nano-TiB2 modified AlSi10Mg sample exhibits fine equiaxed grains, no preferred crystallographic texture and remarkably reduced anisotropy. Besides, both tensile strength and ductility have been improved in the SLMed TiB2 decorated AlSi10Mg sample. The preliminary mechanism upon grain refinement effect due to nano-TiB2 particles on columnar-to-equiaxed transition and reduction of anisotropy was discussed.

Assessment of the performance of TiB2 nanoparticles doped cBN-TiN-Al-Co composites by high temperature high pressure sintering

In this study, cBN composites incorporating TiN–Al–Co were synthesized via high temperature and high pressure (HPHT) methods. TiB2 nanoparticles were employed to optimize cBN cutting tools capacity for precise cutting. The effects of TiB2 nanoparticles on the preparation and properties of cBN composites were comprehensively investigated. The results show that the presence of TiB2 nanoparticles uniformly distributed in the interface not only promotes the formation of AlCo but also inhibits crack propagation, which contributed to the enhanced mechanical properties. With the appropriate addition of TiB2 nanoparticles, cBN composites obtained the compact and fine microstructure and presented better mechanical properties. Consequently, cBN composites incorporating 6 wt% TiB2 nanoparticles exhibited excellent relative density of 99.81%, bending strength of 731 MPa, hardness of 49.5 GPa, fracture toughness of 7.4 MPa⋅m1/2, and abrasive ratio of 2.1. Such composites with outstanding mechanical properties might be promising for cutting tools.

On the Study of a TiB&lt;sub&gt;2&lt;/sub&gt; Nanoparticle Reinforced 7075Al Composite with High Tensile Strength and Unprecedented Ductility

Strength and ductility are the two most important mechanical properties of a structural material. However, they are often mutually exclusive. In this study, a 6 wt. % TiB2 nanoparticle reinforced 7075Al (i.e. TiB2/7075Al) composite was designed and produced by the processing route combining casting, friction stir processing, hot extrusion and T6 heat treatment. The result of tensile testing demonstrates that the as-processed composite sample presents an ultimate tensile strength of 677 MPa and a total elongation to failure of around 15 %, being higher than any Al or Al based materials ever reported. The typical microstructure contains the TiB2 reinforcement nanoparticles uniformly distributed in the equiaxed Al grain matrix (2 μm in average grain size). In addition to the dispersed nanoprecipitates of the 7075Al (Al-Zn-Mg-Cu) matrix, the integrated TiB2 nanoparticles are systematically decorated by a shell corresponding to (Zn1.5Cu0.5)Mg. This finding challenges our understanding and opens a door for further enhancing strength and ductility being easily scalable for industrial applications.

Reinforcement of TiB2 Nanoparticles in Aluminium Piston Alloys for High Performance at Elevated Temperature

Nano-TiB2 particles produced by in situ approaches were employed to reinforce the Mahle 174 piston alloy. Experimental results showed that, with TiB2 nanoparticles, the mechanical properties were significantly improved at ambient and elevated temperatures. The ultimate tensile property at room temperature was increased from 250 to 332 MPa. The ultimate tensile property at 300 °C was increased from 121 to 174 MPa, and that at 350 °C was increased from 86 to 116 MPa. The increase was 82 MPa at ambient temperature, 53 MPa at 300 °C and 30 MPa at 350 °C, respectively. The mechanism of property improvement in the nanocomposites is attributed to the well-distributed nanoparticles in Al matrix, thermal stability of TiB2 at high temperature and the formation of high density of dislocation network in the vicinity of TiB2/Al interface.

Optimization of the TiB2 plasma dynamic synthesis

Titanium Diboride (TiB2) nanoparticles were obtained by plasma dynamic synthesis in a hypersonic plasma jet. The aim of the work was to optimize synthesis of TiB2 nanoparticles. Firstly, three series of experiments with different ways of a discharge initiation were implemented: 1) using titanium conductors; 2) using carbon fibers; 3) using graphite aerosol (graphitization). Secondly, experiments with different atmosphere gas, which filled the volume of the reactor chamber – Ar and N2 were implemented. Thirdly, there were experiments with different mass ratio of Ti:B precursors using graphitization (26.7:73.3; 45.5:54.5; 61.1:38.9; 86.4:13.6). And finally experiments with 16.9 kJ released energy were implemented. The results showed, that the best of way of initiation an arc discharge is graphitization using Ar with mass ratio Ti:B 26.7:73.3 and input energy − 33.9 kJ. The yield of TiB2 was 93.2% with the smallest particles 56.1 nm.

Novel TiB2-reinforced 316L stainless steel nanocomposites with excellent room- and high-temperature yield strength developed by additive manufacturing

Selective laser melting (SLM) is an emerging additive manufacturing process for fabricating multifunctional parts by locally melting and consolidating powders in a layer-by-layer manner. Its flexibility enables the development of new alloys and metal matrix composites with unique, fine microstructures and complex-shaped components that are all difficult to realize with traditional manufacturing processes. This study investigates how TiB2 nanoparticle reinforcements affect the microstructure and high-temperature deformation behavior of a 316L stainless steel matrix. In SLM-processed pure stainless steel, fully directional columnar grains were observed, whereas TiB2 nanoparticles added to the steel matrix significantly reduced the sizes of the molten pools and grains and disrupted the directional structures. A chemical analysis revealed no compositional difference between the boundary and interior of the molten pool areas of the SLM-processed TiB2/316L nanocomposites, suggesting that elements did not segregate macroscopically. However, for higher TiB2 contents, alloying elements microsegregated at the boundaries of cellular structures due to the particle accumulation structure mechanism. Transmission electron microscopy confirmed the existence of mostly cube-like TiB2 nanoparticles both at the boundaries and in the interiors of the cellular structures. The nanocomposites exhibited high compressive yield strength and ductility at room and high temperatures, except at 600 °C, where embrittlement was observed. Observing the microstructure and flow stress of nanocomposites deformed at 700 and 800 °C shed light on the dynamic recovery and dynamic recrystallization phenomena. However, several conventional strengthening mechanisms could not predict the entire yield strength increase. Thus, a novel microsegregation strengthening mechanism was presented to explain the effect of TiB2 on the refined microstructure, and the novel microsegregation phenomenon and the enhanced mechanical properties were correlated. Hence, the SLM process shows high potential for fabricating new materials with outstanding properties.

Enhanced hardness and wear property of S136 mould steel with nano-TiB2 composites fabricated by selective laser melting method

S136 mould steel with excellent corrosion resistance has been widely applied in the mould industry. However, in order to meet the increasing demands of injection products with complex structure and high quality, selective laser melting (SLM) as a novel manufacturing method is chosen due to its rapid fabricating parts with complex geometric shapes. Further, it is essential to enhance their hardness and wear property to prolong the service life of injection mould. In this work the reinforced S136 mould steel with different TiB2 contents (0, 0.5, 1.5, 2.5 wt%) are fabricated by SLM. The optimal TiB2 content is determined to be 0.5 wt%, which the SLM S136 composites show the finest grains and have an enhanced tensile strength (982.8 Mpa), an elevated micro-hardness (761.5 Hv), a reduced coefficient of friction (0.6489) and a considerably low wear rate (0.152 × 10−4 mm3/N m). Here we demonstrate that these superior performances benefited from the novel microstructure, that is, the dispersed TiB2 nanoparticles bonded with each other in a highly homogeneous way to form refined, continuous and well-distributed ring-like structures, which were comprised of thin “metal-ceramic” interface along the grain boundaries. It mainly contributed to the grains refining and grain boundaries strengthening.

Facile synthesis of 10 nm surface clean TiB2 nanoparticles

Nanoscale titanium diborides (TiB2) can be utilized in numerous applications ranging from wear resistant coating to conducting polymers. However, a surface-clean TiB2 nanoparticles with less than 10 nm in size is not currently available in either commercial or literature. Here we report a novel yet scalable synthesis of ultra-fine and uniform size TiB2 nanoparticles (less than 10 nm) by magnesio-reduction of titanium dioxide (TiO2) and boron trioxide (B2O3) in a eutectic lithium chloride/potassium chloride (LiCl/KCl) molten salt. The TiB2 nanoparticle is confined to the nanoscale owing to the partial dissolution of magnesium (Mg) and B2O3 in the molten salts which resulted in reduction on the surface of the TiO2 nanoparticles. The TiB2 nanoparticles size was statistically determined to be 8.1 ± 1.4 nm by analyzing transmission electron microscopic (TEM) images obtained from several samples. High resolution TEM and X-ray diffraction (XRD) study confirm the presence of the surface-clean TiB2 nanoparticles. This novel, simple, and scalable approach has a tremendous potentials for large volume production of ultrafine TiB2 nanoparticles to serve wide range of industries.