TiH2 Particles Research Articles

Microstructure and properties of multiple hybrid reinforced CNTs-TiB2-TiC/Cu laminated composites

Cu matrix laminated composites reinforced with CNTs exhibit excellent mechanical properties; however, the Cu matrix between the laminated structures suffers from insufficient strength. To improve the strength of the matrix and the laminated structure in CNTs/Cu laminated composites, TiH2 and B4C particles were introduced into the Cu matrix via mixing powder, adsorption, hot-pressed sintering and cold rolling, furnishing CNTs-TiB2-TiC/Cu laminated composites. The tensile strength of the CNTs-TiB2-TiC/Cu laminated composites (513 MPa) increased by 26.04 % and 81.27 % compared with those of CNTs/Cu-Ti laminated composites (407 MPa) and CNTs/Cu laminated composites (283 MPa), and the elongation was 18.47 %. The in situ generated TiB2 and TiC reinforcement particles dispersed in the matrix materials induce particle strengthening, enhancing the dislocation density and load-bearing effect. Meanwhile, the CNTs with a laminated structure transfer and share the load. This multiply hybrid reinforcement structure of dispersed TiB2 and TiC particles along with CNTs lamination improves the mechanical properties of the resulting CNTs-TiB2-TiC/Cu laminated composites.

Pre-hydrogenation metallurgy for Ti-3Al-5Mo-4.5V alloy with high density and mechanical properties

The present work proposes a novel master-alloy pre-hydrogenation powder metallurgy (MAPH) method to fabricate the TC16 (Ti-3Al-5Mo-4.5V) alloy, which overcomes the challenge of low sintering density due to the high percentage of alloying powders (APs) and the presence of Mo element. The relative density of sintered TC16 alloys increases with the Ti-addition in APs, i.e., ∼99.2% and ∼99.4% for sintered TC16 alloys based on pre-hydrogenated 7.5Ti-3Al-5Mo-4.5V (7.5TiMA-Hx) and 12.5Ti-3Al-5Mo-4.5V (12.5TiMA-Hx) powders, respectively. The APs were successfully modified to be brittle and hydrogen-containing, which exhibits similar pressing and sintering characteristics as TiH2 powders. The increased relative density could be ascribed to the brittleness of 7.5/12.5TiMA-Hx, in which particles show sharp corners that can form interlocked structures with TiH2 particles during pressing. Furthermore, the 7.5/12.5TiMA-Hx and TiH2 powder particles release H2 and shrink simultaneously during sintering, which minimizes the difference in volume mismatch between particles and promotes elemental diffusion. The sintered TC16-7.5TiMA-Hx alloy achieves excellent mechanical properties, i.e., an ultimate tensile strength of ∼1004.6 MPa, a yield strength of ∼934.2 MPa and an elongation of ∼15.8%, due to the low porosity and acceptable impurity contents. However, the excessive O and N elements in the sintered TC16-12.5TiMA-Hx alloy can induce premature intergranular fracture, resulting in decreased ductility. Therefore, the innovative MAPH technique is promising in obtaining high density sintered Ti alloys with excellent mechanical properties.

Effect of TiH2 Particle Size on Properties of Emulsion Explosive

Effect of TiH2 Particle Size on Properties of Emulsion Explosive

Microstructure and Mechanical Properties of a Novel Al-Mg-Sc-Ti Alloy Fabricated by Laser Powder Bed Fusion.

(TiH2 + ScH3)/Al-Mg composite powders with different Ti contents were produced by ball milling. These composite powders were fabricated to cube and cuboid shape samples via a laser powder bed fusion process with optimal processing parameters. The TiH2 and ScH3 particles underwent dehydrogenation during the laser powder bed fusion process, and these composite powders ultimately formed Al-Mg-Sc-Ti alloys. The relative density, printability, microstructure, hardness and tensile properties of these alloy samples were investigated. The results show that these Al-Mg-Sc-Ti alloys have lower hot-crack sensitivity, having fine equiaxed grains. An Al18Mg3(Ti,Sc)2 intermetallic phase and in situ L12-Al3(Sc,Ti) precipitations formed during the laser powder bed fusion process, which is beneficial for nucleation and dispersion strengthening. The ultimate tensile strength of the Al-Mg-0.7Sc-1.0Ti alloy was 313.6 MPa with an elongation of 6.6%. During the hot isostatic pressing treatment, most of the Mg element precipitated from the matrix and changed the Al3(Sc,Ti) into a Al18Mg3(Ti,Sc)2 precipitate completely. The Al-Mg-Sc-Ti alloys were nearly fully dense after the hot isostatic pressing treatment and exhibited better mechanical properties. The ultimate tensile strength of the Al-Mg-0.7Sc-1.0Ti was 475 MPa with an elongation of 8.5%.

Fabrication of Uniform and Rounded Closed-Cell Aluminum Foams Using Novel Foamable Precursor Particles (FPPs)

The powder metallurgy (PM) route for the production of closed-cell metallic foams has recently received a significant amount of attention. One of the major issues is the non-uniform and non-spherical nature of the cells produced, which can negatively affect the mechanical behavior. The current paper uses the PM route to process metallic foams for the first time using novel Al-TiH2 foamable precursor “particles” (FPPs). The effect of FPP content (0–10 wt.%) on the developed foam structure of aluminum and its mechanical properties is investigated. An increase in FPP content results in a decline in product density by forming uniform and near-spherical cells. The main advantage of the FPPs is the localization of the blowing agent TiH2 particle content within Al-TiH2 composite particles (i.e., giving rise to a higher local TiH2 content), which has led to the production of pores with relatively high circularities even at very low overall TiH2 contents. The foams produced displayed energy absorption capacities of 10–25 MJ/m3 at 50% strain, and maximum energy absorption efficiencies ranging from 0.6–0.7 (for 40–60% closed cell content)

Investigation on the microstructures, mechanical properties and impact initiation characteristics of Al/PTFE reactive materials reinforced by TiH2 particles

Aluminum/Polytetrafluoroethylene (Al/PTFE) is a representative energetic material, which can be used in many fields including defense weapon fragments, insensitive penetrator or oil-well perforation. However, the insufficient mechanical strength of traditional ingredient has seriously restricted its penetration ability, and traditional additives improve its compressive strength at the expense of reactivity. Hence, innovative component design and advanced manufacturing technology should be applied to Al/PTFE composite. In this investigation, TiH2 as a new reinforcement is introduced into Al/PTFE to improve both strength and reactivity. Quasi-static and dynamic compressive tests were conducted, and the impact reaction process was recorded by high-speed camera. The results shown Al/PTFE/TiH2 composites are all elasto-plastic materials, significant strain hardening and strain rate hardening phenomenon were observed. The compressive strength increased first and then decreased with increase in TiH2 content, reached the maximum of 185.1 MPa at the strain rate of 5000 s−1 when TiH2 content was 30 %, which increased by 30.4 % compared to traditional Al/PTFE. A newly-developed drop-weight device was used to quantitatively characterize reactivity, and the reaction efficiency reached 8.2 % when TiH2 content was 30 %, increased by 43.2 % compared to Al/PTFE. The formation of oriented PTFE nano-fibers was considered the important strengthening mechanism. The established Johnson–Cook model was agreed well with experimental results. Combining the results of thermogravimetry-differential scanning calorimetry (TG-DSC) tests with X-ray diffraction (XRD) analysis of reaction residues, the reaction mechanism was clarified. The impact initiation reaction was in a mechano-chemical manner and the reactivity was speculated to be the results of multiple actions between Al/PTFE and TiH2.

Influence of Current Density upon Hydrogenation on the Shape Memory Effect of Binary TiNi Alloy Single Crystals

Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape memory effect (SME) under tension of the [011]-oriented Ti-50.55%Ni (at.%) alloy single crystals are presented. It was shown that hydrogen is in a solid solution and forms particles of titanium hydride TiH2 after hydrogenation at j = 1500 and 3500 A/m2, respectively. Both hydrogen in the solid solution and TiH2 particles led to a decrease in the Ms temperature of the onset of the forward martensitic transformation (MT) upon cooling and the Md temperature (Md is the temperature at which the stresses for the onset of the stress-induced MT are equal to the stresses for the onset of plastic flow of the high-temperature B2 phase), and increased the yield stress σ0.1 of the B2 phase at the Md temperature compared to hydrogen-free crystals. It was found that the SME under stress depends on the tensile stress level and current density. The maximum SME εSME = 10 ± 0.2% at σex = 200 MPa and εSME = 10.5 ± 0.2% at σex = 300 MPa was observed in the hydrogen-free crystals and after hydrogenation at j = 1500 A/m2, respectively, which exceeded the theoretical value of lattice deformation ε0 = 8.95% for the B2-B19′ MT in [011] orientation under tension. At j = 1500 A/m2, the physical reason for the excess of the SME of the theoretical ε0 value was due to the increase in the plasticity of B19′ martensite upon hydrogenation. At j = 3500 A/m2, εSME = 8.0 ± 0.2%, and it was less than ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. The decrease in SME after hydrogenation at j = 3500 A/m2 was associated with the interaction of two types of B19′-martensite: oriented under stress and non-oriented, formed near TiH2 particles. It was shown that the redistribution of hydrogen in the bulk of the crystals during long-term holding for 168 h at 263 K after hydrogenation at j = 1500 A/m2 increases the SME relative to crystals without long-term holding: 3.5 times at 50 MPa and 1.8 times at 100–150 MPa. After long-term holding, εSME = 9.5 ± 0.2% at 150 MPa, which exceeds the theoretical value ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension.

Inhibitory effects of typical inert gases on the flame propagation and structures in TiH2 dust clouds

The inhibitory effects of CO2, N2 and Ar on TiH2 dust explosion had been experimentally studied. The results showed that the inhibitory effects of the three inert gases on the flame morphology, propagation velocity and temperature of TiH2 dust explosion were in the order of CO2 > N2 > Ar under the same oxygen concentration. CO2 accelerated the cooling and extinguishing processes of the incomplete burning particles to inhibit the further dehydrogenation and combustion reactions of TiH2 particles. N2 reacted with TiH2 particles and form ternary Ti-O-N solutions on its surface to hinder the binding progress of TiH2 and O2. In the process of Ar dilution, OH radical was adsorbed on the surface of TiH2-x to enhance its surface reactivity. N2 and CO2 mainly inhibited the explosion of TiH2 dust cloud through dilution of O2, cooling and chemical reactions, whereas Ar mainly played the roles of diluting O2 and cooling.

A novel method to fabricate high strength and ductility Ti-3Al-5Mo-4.5 V alloy based on TiH2 and pre-hydrogenated master alloy powders

Fabrication of high-performance titanium (Ti) alloys containing high-melting-point elements is challenging via blended elemental powder metallurgy (BEPM), because of the inevitable high porosity induced during pressing and sintering processes. Herein, we propose a novel master-alloy pre-hydrogenation (MAPH) method to fabricate sintered TC16 (Ti-3Al-5Mo-4.5 V) alloy, which possess a nearly full-density (99.2%) and good mechanical properties, i.e., an UTS of ∼ 1004.6 MPa, a YS of ∼934.2 MPa and an EL of ∼15.8%. The pre-hydrogenated 7.5Ti-3Al-5Mo-4.5V-Hx (7.5TiMA-Hx) powder particles show a morphology of sharp corners. Therefore, the 7.5TiMA-Hx and TiH2 particles can get interlocked compactly during compaction and shrink simultaneously during the dehydrogenation process, which minimizes the difference in volume mismatch and ensures the overall uniformity after sintering. Besides, the interlocking compact structure makes the element diffusion easier between the 7.5TiMA-Hx and TiH2 matrix particles, which promotes the healing of porosity. The low porosity can reduce the tendency for propagation of cracks along the grain boundaries of the α layer, leading to a good balance between the strength and ductility of the sintered TC16-7.5TiMA-Hx alloy.

The role of TiH2 on microstructure and mechanical properties of Al–Zn–Mg–Cu alloy fabricated by laser powder bed fusion

In this study, a crack-free 7075 aluminum alloy composed of fine, randomly-oriented and equiaxed grains ∼1 μm in size was successfully prepared by laser powder bed fusion (L-PBF). TiH2 particles were introduced to achieve significant grain refinement, serving as a critical method to relieve the high residual stress and prohibit inherent hot cracking during L-PBF manufacturing. Multiscale microstructural characterizations were applied to reveal the mechanisms of grain refinement and elimination of hot cracking. On the one hand, in-situ produced L12-structured Al3Ti particles stimulated heterogeneous nucleation of α-Al. On the other hand, Ti solute atoms played an important role in restricting grain growth during solidification. A conventional T6 treatment was conducted to modify the microstructures and mechanical properties of the alloy. E-Al18Mg3(Ti,Cr)2 dispersoids were precipitated, playing a role in strengthening through pinning grain boundaries. Thanks to grain boundary strengthening and Orowan dislocation strengthening arising from η' precipitates, Al3Ti particles and E dispersoids, the yield strength, ultimate tensile strength and elongation of T6 treated 7075-Ti alloy are 496 ± 10.8 MPa, 537 ± 7.6 MPa and 7.2 ± 0.3 %, respectively. These findings provide a broader insight into the use of TiH2 to improve the microstructure and mechanical properties of L-PBF-fabricated high-strength aluminum alloy.

Cell Structure Improvement in Melt Processed Pure Aluminium Foams by Pre-treatment of Foaming Mixture

This work aims to evaluate the cell structure of aluminium foams blown by using foaming mixture subjected under ball milling and heat treatments. This paper presents the study on the effects of various pre-treatment of foaming mixture on the cell structure of foamed aluminium (Al) fabricated via melt route. This study also demonstrates how the melt foaming method can be used to fabricate small-sized Al foams. Prior to foaming the Al melt, the foaming mixture containing TiH2 and Al was pre-treated by ball milling and heat treatment in four different ways. The foaming mixtures were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX) and Scanning Electron Microscope (SEM) techniques. The macrostructure of the foams has been characterized by optical scanner and ImageJ software. The mechanical properties of the foam samples were evaluated by quasi-static compression test. XRD results revealed the TiO2 and Ti3O phases formed in the heat treated TiH2 powders. SEM micrographs showed the morphological changes occurred to Al and TiH2 powders and their distribution before and after ball milling. EDAX reported the chemical composition of elements present in the foaming mixtures. Ball milled foaming mixture not only increases the number of TiH2 particles, but also reduces the hydrogen content during the foaming stage. The foam produced from heat-treated and ball-milled foaming mixture shows better cell size & structure with good homogeneity. However, the mechanically mixed foaming mixture produce foam with good strength and energy absorption capability.

Microstructure evolution and decomposition behavior of an novel core-multi-shell structure TiH2 foaming agent

Al foams have received an increasing attention due to their light weight, high specific strength, energy absorption, sound absorption, damping and electromagnetic shielding. However, the issue of low mechanical property is still a challenge due to the mismatch between the melting point of Al and Al alloys and the decomposition temperature of TiH2 blowing agent. In this work, an novel TiH2 foaming agent with core-multi-shell structure (TiH2/Ti3O@TiO2/BPR) was prepared by thermal oxidation and coating boron phenolic resin (BPR) treatment. The results showed that the composite layers of Ti3O@TiO2 with a thickness about 70 nm and BPR with a thickness about 200 nm were formed on the surface of TiH2 particles which can act as an excellent thermal and diffusional barrier to retard the heattransfer and delay the release of hydrogen. Compared with as-received and pre-oxidized TiH2 particles, TiH2/Ti3O@TiO2/BPR particles exhibited an excellent slow release property and its peak temperature of hydrogen release and corresponding time are about 647 °C and 1801 s, which increased by about 83 °C and 176 s, 44 °C and 59 s, respectively. The hydrogen release temperature matched well with the melting point of Al and Al alloys, which is very suitable for preparing high quality Al foams.

Preparation of complex shaped aluminum foam by a novel casting-foaming method

A novel casting-foaming (CF) method based on melt foaming route is proposed in this study to prepare aluminum foam parts with complex shape. A foamable and flowable precursor alloy melt (PAM) was prepared by dispersing pre-oxidized TiH2 particles into a thickened Al-Si-Mg eutectic alloy melt, whose liquidus temperature is compatible with the decomposition temperature of pre-oxidized TiH2. Afterwards, the PAM was poured into a heated mold and foamed to fill the mold cavity, followed by solidification. Particle distribution in the precursor and shaping capacity of the CF method were examined. Results show that TiH2 particles can be well dispersed in the precursor without aggregation. The shaped foam parts with submillimeter scale of arc radii at angle (45°, 60° and 90°) tips were obtained, showing an extreme filling capacity of the CF method.

Nucleation and growth of gas bubbles in AlSi8Mg4 foam investigated by X-ray tomoscopy

Initiation and growth of metal foam is a complex and dynamical process, which is intrinsically three-dimensional and time-dependent. Tomoscopy –or time-resolved tomography– allows us to follow the nucleation and growth of gas bubbles in AlSi8Mg4 alloy in real time during foaming. The location, size and shape of individual bubbles was determined in steps of 1 s with spatial resolutions of a few µm. Moreover, the constituents responsible for gas evolution, namely Al-Mg phases and TiH2 particles, were identified in the series of 3D images. Automated quantitative image analysis of bubbles and gas-generated phases including their spatial correlations allowed us to break down the foaming process into two distinct steps, a first homogenous one driven by adsorbed gases and first melting microstructural components and a second attributed to the melting of the alloy and subsequent foam growth driven by hydrogen released from TiH2 particles. The results of the study indicate that standard AlSi8Mg4 foam can be improved by tailoring the properties of the Al-Mg constituent powder.

Influence of Ti and TiH2 Additives on the Structure and Properties of Copper Alloys for Diamond Cutting Tools

The influence of titanium and titanium hydride additives on the structure, mechanical properties, and wear resistance of copper alloys intended for use as a binder of the diamond cutting tool is investigated. Powder mixtures Cu–Ti and Cu–TiH2 are fabricated by mechanical alloying in a planetary centrifugal mill. Such treatment makes it possible to form single-phased powders of the copper-based solid solution in the Cu–Ti system and two-phased powders based on copper with uniformly distributed TiH2 particles in the Cu–TiH2 system. It is established that the maximal mechanical properties are characteristic of the samples of compositions Cu–2.5% Ti and Cu–10% TiH2 (higher than for pure copper by a factor of 2.0–3.5). Hardening in such alloys is implemented according to the solid-solution mechanism and due to the formation of the Cu3Ti3O phase. Grains of this phase have higher dispersity in alloys where TiH2 is used as the titanium-containing additive, due to which high values of the bending ultimate strength (920 MPa) and hardness (114 HB) are attained. It is established according to the results of comparative tribological investigations that samples of the Cu–10% TiH2 composition possess the best wear resistance. The reduced wear of these samples after the test according to the “rod–disc” scheme is an order of magnitude lower than for pure copper and lower by a factor of 5 than for Cu–2.5% Ti samples.

Manufacturing of Conductive, Wear-Resistant Nanoreinforced Cu-Ti Alloys Using Partially Oxidized Electrolytic Copper Powder.

Reactive powder composites Cu-(0–15%)TiH2 containing up to 5% native Cu2O were manufactured by high energy ball milling and then hot-pressed to produce bulk nanostructured copper–matrix alloys reinforced by Cu3Ti3O inclusions. Two high-energy ball-milling (HEBM) protocols were employed for the fabrication of Cu-Ti alloys: single-stage and two-stage ball milling, resulting in an order of magnitude refinement of TiH2 particles in the reactive mixtures. Single-stage HEBM processing led to the partial retention of Ti in the microstructure of hot-pressed specimens as the α-Ti phase and formation of fine-grained (100–200 nm) copper matrix interspersed with 5–20 nm Cu3Ti3O precipitates, whereas the two-stage HEBM led to the complete conversion of TiH2 into the Cu3Ti3O phase during the hot pressing but produced a coarser copper matrix (1–2 μm) with 0.1–0.2 μm wide polycrystalline Cu3Ti3O layers on the boundaries of Cu grains. The alloy produced using single-stage HEBM was characterized by the highest strength (up to 950 MPa) and electrical conductivity (2.6 × 107 Sm/m) as well as the lowest specific wear rate (1.1 × 10−5 mm3/N/m). The tribological performance of the alloy was enhanced by the formation of Cu3Ti3O microfibers in the wear debris, which reduced the friction coefficient against the Al2O3 counter-body. The potential applications of the developed alloys are briefly discussed.

Structural heterogeneity and its effects on the properties of an in situ TiB2–TiC/Cu composite synthesised by hot pressing

ABSTRACTIn situ TiB2 and TiC reinforced copper matrix composites with tailored heterogeneous structure were fabricated via high-energy ball milling of Cu, TiH2 and B4C powders followed by hot pressing. The microstructures of both ball-milled powders and hot-pressed composites were compared. Although the dislocation density of Cu matrix was changed after hot pressing, the mode of distribution of ceramic phases in the Cu matrix was noted to transmit from the ball-milled powders to hot-pressed composites in case of the TiH2 particles synthesised by the in situ reactions. The structural inheritance between the ball-milled powders and hot-pressed composites could be used to control microstructural features and thus to tune properties. The hot-pressed TiB2–TiC/Cu composites with tailored heterogeneous structure exhibited better performance than those of homogeneous counterparts.

Role of various pretreatment processes in electroless nickel deposition on TiH2 particles with a simple plating bath

Electroless nickel was successfully deposited on TiH2 particles with a simple plating bath which contains only a nickel salt NiCl2 and a strong reductant dimethylamine borane (DMAB) and the effect of various pretreatment processes was studied. The three different pretreatment processes include: (1) a two-step pretreatment with SnCl2 sensitization followed by PdCl2 activation (SnCl2–PdCl2); (2) only PdCl2 activation, and (3) without pretreatment (direct electroless deposition). The characteristics of TiH2 powders before and after nickel deposition were analyzed with field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). It was found that except for the traditional SnCl2–PdCl2 pretreatment process, the pretreatment with only PdCl2 activation and direct electroless nickel deposition without any pretreatment of the powder surface can both lead to continuous and homogeneous nickel layer on TiH2 powders. This may be due to the strongly negatively charged powder surface with its very low isoelectric point (I.E.P.) which promotes the adsorption of Ni2+ from the plating bath onto powder surface. On the other hand, the strong reducing agent DMAB facilitate the reduction of Ni2+ ions even without Pd catalysation. This work provides a simplified and alternative way for electroless nickel coating on TiH2 powders with the application in aluminium foaming.

Core/multi-shell particles based on TiH2, a high-performance thermally activated foaming agent

The key element in the production of metal foams is the availability of a gas provider, which must be able to release the gas once the metal reaches the liquidus temperature, allowing the homogeneous formation of pores in a narrow size distribution. TiH2 is by far the most widely used foaming agent for aluminium alloy foaming; however, this compound starts to release hydrogen during heating below 450 °C, and the liquidus temperature of aluminium alloys is above 600 °C. In this work we studied the formation of a core/shell structure based on TiH2 particles. The best results were obtained with a TiH2/Ti3O@TiO2/SiO2 core/multi-shell structure, which starts to release hydrogen around 600 °C.

Examination of microstructure evolution and strengthening mechanisms in an aluminum-based hybrid composite prepared through the spark plasma sintering method

A bulk hybrid composite to be potentially used as a foam precursor was produced in this study. TiH2 powder particles along with different concentrations of SiC were mixed with pure Al particles and consolidated through the spark plasma sintering (SPS) method. Bulk samples with nearly full density were successfully produced using the SPS method. During the consolidation process, no additional phases were found within the ceramic particles/matrix interfacial region. Using the ceramic TiH2 and SiC particles as the reinforcement cause notably strengthened the pure Al matrix (37% higher yield strength) without adversely affecting the plasticity, helping retain strain to fracture of about 50% for the sample. The yield strength of the samples was quantitatively approximated by examining their strengthening mechanisms via a number of simplified models available in the literature. The analyses found grain boundary and dislocation strengthening to be the most effective mechanisms for enhancing the strength of the samples; it was also found that the difference between the approximated and experimentally obtained overall yield strength was negligible.