Boron Addition Research Articles

Grain refinement of wire arc additive manufactured titanium alloy by the combined method of boron addition and low frequency pulse arc

Abstract The columnar to equiaxed transition (CET) of grain structures has been a great challenge during titanium alloy additive manufacturing (AM), especially for wire arc additive manufacturing (WAAM) with the highly localized heat input and large temperature gradient. In this work, three combined methods (ultrahigh frequency pulse arc + growth restricting solutes (GRS) additions (HP–S method), ultrasonic vibration + GRS additions (UV–S method) and low frequency pulse arc + GRS additions (LP-S method)) were investigated and compared for the capacity of refining β columnar grains and weakening α texture during the titanium alloy WAAM process. Compared with the other two methods, the LP-S method has a dramatic effect on achieving CET and weakening α texture. During the solidification process of LP-S method, three stages can be divided: (1) nucleation stage (2) competitive growth stage (3) re-melting stage, which promote CET and weaken α texture. It can be anticipated that further optimization in the selection of alloy elements and the process parameters of the low frequency pulse arc (base current, peak current and pulse frequency, etc.) can achieve grain morphology control and mechanical properties improvement.

Enhancing the mechanical features of poly(vinyl) alcohol nanofibers with the addition of boron nitride

Improvement of nano-sized products with boron additives with remarkable properties has become a popular trend for many different application areas. Here, we have reported an efficient poly(vinyl alcohol) (PVA) based composite nanofiber which was functionalized with the hexagonal boron nitride (h-BN) via electrospinning technique, for the first time as far as known, for body-armor and protective clothing applications. PVA-based composite nanofibers containing h-BN with a diameter of approximately 326 nm have shown significant mechanical features compared to pure PVA nanofibers with a diameter of about 223 nm. Mechanical features were investigated by nanoindentation and the results of nanoindentation demonstrated that the elastic modulus of PVA nanofibers increased by 77%, and hardness values of polymeric nanofibers reached ten times more, by the addition of h-BN. FTIR and XRD characterizations approved that there is no chemical change of h-BN when it was integrated into the PVA based composite nanofibers. We exceptionally believe that the achieved results offer a potential lightness and cost-effective strategy for body armor and protective clothing applications in contrast to boron carbide-based body armor products, which have main problems such as weightiness and high-priced.

Simultaneous enhancement of strength and ductility of body-centered cubic TiZrNb multi-principal element alloys via boron-doping

Body-centered cubic (BCC) multi-principal element alloys (MPEAs) have intrinsic high strength but poor ductility, which greatly limits their potential applications. Here we present the boron-doping strategy to enhance the strength and ductility of TiZrNb MPEAs simultaneously. The yield strength and ductility of the TiZrNb MPEA with boron addition of 500 ppm are increased by 19.0 % and 48.7 % compared to the boron-free TiZrNb MPEA, respectively. Boron-doping induced high efficiency in grain refinement from ∼96.0 μm to ∼16.2 μm is the main factor for strengthening. Dislocation dominated deformation mechanism involving cross slip and dislocation pining in the TiZrNb containing 500 ppm boron serves to enhance the strain-hardening capacity, resultant the enhancement of ductility from 7.8 % to 11.6 %. While the planar slip of dislocations is the dominated deformation mechanism for the boron-free TiZrNb.

Effects of B content on microstructure and high-temperature stress rupture properties of a high chromium polycrystalline nickel-based superalloy

Effects of boron (B) addition on microstructure and high-temperature stress rupture properties of a heat-treated high chromium polycrystalline Nickel-based superalloy were investigated by adjusting B content (0, 0.016 wt%, 0.048 wt%, 0.09 wt%). The results indicated that the grain boundary characteristics were altered by B addition, such as the morphologies of the MC carbides, M23C6 carbides and precipitation of γ′ particles along grain boundaries. Meanwhile, it was confirmed that B existed in the form of Cr-rich M5B3 borides in the boron-containing alloys. Moreover, boron addition aggravated the inhomogeneity of microstructures, and reduced the volume fraction of secondary γ′ particles. Additionally, the rupture life was remarkably improved as the B content was increased to 0.016 wt%, whilst the elongation tended to improve as the B content was increased to 0.048 wt%. The improvement of stress rupture properties was mainly contributed to the modification of the grain boundary characteristics which retarded crack nucleation and propagation at grain boundaries. However, with excessive addition of B, the stress rupture properties were reduced significantly, as the solid solution strengthening and precipitation strengthening tended to be weakened by B addition, in addition the incipient melting regions and lager size borides promoted the intragranular crack nucleation and propagation.

Understanding the setting and hardening process of wollastonite-based brushite cement. Part 2: Influence of the boron and aluminum concentrations in the mixing solution

The mixing solution of wollastonite-based brushite cement is a phosphoric acid solution containing metallic cations and borax. This work complements a previous study devoted to the influence of the H3PO4 concentration, Ca/P and liquid-to-solid (l/s) ratios on the setting and hardening process of the binder by providing new insight into the role of aluminum and boron.Boron retards the setting and decreases the heat released during the process. It also contributes to reduce the macroporosity of the hardened material but yields to poor compressive strength. With aluminum in the mixing solution, the mechanical properties are greatly improved thanks to the precipitation of an amorphous aluminophosphate which increases the density of the cement matrix. But aluminum alone leads to fast setting. A joint addition of boron and aluminum to the mixing solution makes it possible to get a material with optimized properties both in fresh and hardened states.

Influences of boron contents on microstructures and mechanical properties of as-casted near α titanium alloy

Ti-6.5Al-2.5Sn-9Zr-0.5Mo-0.25Si-1Nb-1W-0.1Er-xB (x = 0, 0.1, 0.2, 0.4, 0.6 and 0.8 wt%) with different boron contents are fabricated for investigation. Influences of boron element and its amounts on phase constitutions, microstructures, textures and compression mechanical properties are carefully studied. With the increasing boron additions, contents of TiB phase increase, and the maximum intensities of textures decrease. Microstructures are significantly and continuously refined after adding boron element and with the increasing boron additions, and turning point of refinement rates for different microstructural parameters is found at 0.2 wt% boron content. Strengths increase monotonously, while elongations increase firstly and decrease afterwards. The maximum value of elongation is acquired at boron content of 0.2 wt%. On the premise of ensuring plasticity, 0.2 wt% boron content is the most appropriate amount for microstructural refinement and mechanical properties enhancement for current near α titanium alloys. Meanwhile, aspect ratios of TiB whiskers increase with the increasing boron contents. Lots of near equiaxed α grains or α grains with irregular morphologies are discovered around TiB phase. Distorted and twisted α grain boundaries are also obviously detected in boron containing alloys. Moreover, premature fracture of alloys containing TiB whiskers is largely influenced by the fracture of these brittle reinforcements.

Effects of boron on microstructure and properties of microwave sintered FeCoNi1.5CuY0.2 high-entropy alloy

The mechanical properties of high-entropy alloys (HEAs) containing rare earth are improved by adding boron element. Under the condition that the content of rare-earth is fixed, FeCoNi1.5CuY0.2Bx high-entropy alloy with different boron atom ratios (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) is prepared by advanced microwave sintering process. The effect of boron addition with different atomic ratios on the phase evolution, microstructure, compressive mechanical properties and magnetic properties of the FeCoNi1.5CuY0.2 high-entropy alloy is emphatically studied. The results show that the phase transformation temperature decreases with the increase of boron content, which is conducive to the rapid sintering at low temperature. When boron content is less than 0.4 atomic ratio, the alloy is dominated by FCC base phase and BYO3, eliminating the oxidation phase of Y2O3. When boron adding amount as x = 0.4, it has the largest maximum compression ratio. When the amount of boron exceeds 0.4 atomic ratio, boride precipitates in the alloy, which increases the strength and hardness and at the cost of plasticity and soft magnetism. When the amount of boron is x = 1, the hardness arrives at utmost, and the compressive strength, yield strength and hardness are 1546 MPa, 1112 MPa and 367.1HV, respectively, which are 150%, 129% and 29.03% higher than those of boron-free sample. The improvement of mechanical properties is due to the fact that boron with small atomic size is easy to solute into the FCC base phase, forming interstitial solid solution, which results in lattice distortion and solid solution strengthening effect. And BY12 particles precipitated in BYO3 have dispersion strengthening effect on the alloy.

Effect of Boron on the Microstructure Evolution and Dynamic Recrystallization Kinetics of ALLVAC718Plus Superalloy

In this study, the effect of boron addition on the hot compression behavior and dynamic recrystallization kinetics of 718Plus nickel-based superalloy were investigated by isothermal compression tests at the deformation temperature range of 900-1050 °C and strain rate range of 0.01-1 s−1. Optical and field emission scanning electron microscopy techniques were employed to investigate the microstructural evolutions. The results indicated that the addition of boron reduces the flow stress of 718Plus superalloy. This could be attributed to the decrease in the volume fraction of Ni3(Al, Ti) particles. Microstructural observations revealed more volume fraction of dynamic recrystallization in the boron-bearing alloy at low-deformation temperatures, i.e., 900 and 950 °C. In contrast, at high temperatures of 1000-1050 °C, recrystallization is retarded mainly due to the segregation of boron to the grain boundaries.

Influence of boron on microstructure and mechanical properties of Gleeble simulated heat-affected zone in P91 steel

In the present endeavor, a Gleeble thermo-mechanical simulator has been used to simulate subzones of the heat-affected zone (HAZ) of boron-free P91 and boron-modified P91B steels to investigate the influence of boron on microstructure and mechanical properties. The prior austenite grain (PAG) size remained similar to that of parent metal in the fine-grained heat-affected zone (FGHAZ) and inter-critical heat-affected zone (ICHAZ) of P91B steel. The microhardness value of simulated specimens, including parent metals was observed to be similar. But impression creep resistance of boron-containing steel was significantly higher than that of the boron-free steel. The presence of boron decreased precipitates size and increased fraction of low energy Σ3 coincident-site lattice (CSL) boundaries that attributed to improvement of creep resistance. However, there was a slight reduction in solid solution hardening due to increased area fraction of precipitates in parent metal and simulated specimens of boron-containing steel. Hindering of alloy element partitioning during impression creep of P91B-ICHAZ was observed, which was possibly due to the presence of boron in soluble form in the iron matrix and the segregated form on grain and sub-grain boundaries (SGBs). Further, the addition of boron was observed to retard M23C6 precipitate coarsening in the P91B-ICHAZ in comparison to its P91 version.

Study of boron doped amorphous silicon lightly hydrogenated prepared by DC magnetron sputtering for infrared detectors applications

The objective of this study is to investigate the effect of boron doping concentration on the bolometric properties of lightly hydrogenated amorphous silicon doped with boron (a-Si: H(B)) films. Thin film a-Si: H(B) samples with different boron concentrations are prepared by co-sputtering of boron and silicon at relatively low hydrogen pressure. FTIR analyses show that the intensity of the characteristic peak of the substitutional boron gradually increases with the addition of boron. Increasing in boron concentration affects the bolometric properties of the lightly hydrogenated a-Si: H (B) films, including conductivity at room temperature (σRT) and thermal resistance coefficient (TCR). Indeed, when the boron concentration increases from 1.5 to 43%, σRT increases from 1.4 10−6 to 2 10−3 Ω−1 cm−1 while the absolute value of TCR decreases from 3% to 8% K−1, respectively. In addition, lightly hydrogenated a-Si: H (B) films exhibit good thermal stability. We have showed in this study that lightly hydrogenated a-Si: H(B) can be considered as a potential candidate for low-cost, high-performance uncooled micro bolometers.

The Effect of Boron Addition on The Microstructure and Corrosion Resistance of Cu-Al-Ni Shape-Memory Alloys Prepared by Powder Technology

Due to their promising mechanical characteristics, copper-based shape-memory alloys (SMAs) are crucial for numerous applications. This research inspects the outcomes of various quantities (0.4%, 0.8% and 1.2% wt) of boron (B) additions on the resistance against corrosion and the microstructure of Cu-Al-Ni SMAs using SEM, EDS, XRD and electrochemical tests in a solution of 3.5% NaCl. Numerous measurement baths were used for aged / unaged Cu-Al-Ni-xB SMAs. The electrochemical tests were performed over several periods to confirm the reliability of the corrosion-resistance property, after which the samples were verified using solutions of 3.5% NaCl. The experimental results demonstrated that adding 1.2% wt B followed by an ageing process resulted in an improvement in the corrosion resistance in Cu-Al-Ni SMAs and a decrease in the corrosion rate by 58%.

Boron doped Hydroxapatites in Biomedical Applications

Hydroxyapatite has been widely used in biomedical applications as a coating material for implant surfaces, a drug carrier, a scaffold or composite for bone tissue engineering applications. The highly ionic structure of hydroxyapatite allows doping of various ions, resulting in an improvement in its properties. Boron is one of the elements which can be doped into hydroxyapatite structure by replacing phosphate (PO43-) or hydroxyl (OH-) sites to obtain scaffolds for bone tissue engineering applications or a coating material for metal substrates. Although the effects of supplemental boron on bone, liver, and brain metabolism have been shown to have important results as a nutrient, there are very few studies in the literature on the use of boron-doped hydroxyapatite in the biomedical field. In this review, the details of synthesis methods and functional groups of boron-doped hydroxyapatite were tabulated. Generally, the addition of boron leads to the formation of rod-like morphology, while the density and Vicker’s microhardness of hydroxyapatite decrease. Thermal stability and electrical insulation properties were observed to improve with boron doping. Boron was also shown to increase biodegradability, bioactivity as well as cell proliferation and differentiation of different cell types on the surface of hydroxyapatite.

Enhancement of strength-ductility balance of heavy Ti and Al alloyed FeCoNiCr high-entropy alloys via boron doping

As one of the most effective mechanisms, precipitation-hardening is widely used to strengthen high-entropy alloys. Yet, heavy precipitation-hardened high-entropy alloys usually exhibit serious embrittlement. How to effectively achieve ultra-high strength and maintain reliable ductility remains a challenge. Here, we report a study of doping extremely little boron to meet this target. We found that adding of 30 ppm boron into the heavy Ti and Al alloyed FCC FeCoNiCr high-entropy, (FeCoNiCr)88Ti6Al6 HEA (at.%) which is strengthened mainly by both coarse BCC-based (Ni, Co)2TiAl Heusler and fine L12-type FCC-based (Ni, Co)3TiAl precipitates and shows ultrahigh strength but poor ductility, could significantly change the original microstructure and consequently improve mechanical performance, owing to the well-known effect of boron on reducing the energy of grain boundaries. The boron addition can (1) eliminate microcavities formed at Heusler precipitate-matrix interfaces; (2) suppress the formation and segregation of coarse BCC Heusler precipitates; (3) promote the formation of L12 nanoparticles. This changes of microstructure substantially improve the tensile ductility more than by ∼86 % and retain comparable or even better ultimate tensile strength. These findings may provide a simple and costless solution to produce heavy precipitation-strengthened HEAs with ultrahigh strength and prevent accidental brittleness.

Effect of B addition on the superelasticity in FeNiCoAlTa single crystals

The study focuses on the superelastic effect in single-crystalline boron-doped Fe-based shape memory alloys. The homogenized and quenched single crystals were subjected to a heat treatment at 973 K for variable aging times. As a result, small and coherent nanometer-sized γ′ (Ni3Al-type) precipitates were formed. It was established that Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B single crystals oriented along [001] direction exhibit the fully reversible superelastic behavior up to 14.3% compression strain at 77 K reaching the maximum theoretical value. The boron addition suppressed completely the formation of the brittle β phase and reduced the average precipitate size of the γ′ precipitates. Using high-energy synchrotron radiation and high-resolution transmission electron microscopy analysis the volume fraction and precipitate size of γ′ were determined indicating that both factors are critical in obtaining the largest superelastic reversibility. Boron addition counters the initial effect of mechanical stabilization which was detected in single crystals without boron. Unlike the thermally induced martensitic transformation, applied stresses produce a different austenite/martensite interface composed of interchanging austenite and martensite variants. It is also demonstrated that upon loading/unloading cycles the moving transformation front divides the material into three district regions i.e. single variant of austenite, austenite intermixed with martensite and single variant of martensite.

Switching the magnetostructural coupling in MnCoGe-based magnetocaloric materials

We performed neutron-diffraction experiments and density functional theory calculations to study the magnetostructural coupling in MnCoGeBx (x=0, 0.01, and 0.05) alloys. By varying the amount of boron addition, we are able to freely switch the magnetostructural coupling on and off in the MnCoGe alloys. It is found that the boron addition stabilizes the high-temperature hexagonal phase due to the reduced interatomic distances and the enhanced covalent bonding. The hexagonal-orthorhombic structural transition shifts to low temperatures with the boron addition and coincides with the paramagnetic-ferromagnetic (PM-FM) transition in the MnCoGeB0.01 alloy. With a further increase in the boron addition, the structural and magnetic transitions are decoupled again. The hexagonal-orthorhombic structural transition is significantly suppressed in the MnCoGeB0.05 alloy, although subtle distortions in the hexagonal structure are evidenced by a canted spin arrangement below 75 K. The MnCoGe and MnCoGeB0.01 alloys show a collinear FM structure, having a much larger Mn moment than the MnCoGeB0.05 alloy. The relatively small Mn moment in the MnCoGeB0.05 alloy can be attributed to the shortened Mn-Mn distance and the enhanced overlap of the 3d orbitals between the neighboring Mn atoms. The uncovered relationship between the structural evolution and the sizable magnetic moment in the present work offers more insight into the magnetostructural coupling in the MnCoGe-based alloys.

Characterization of Microstructure and Phase Elemental Composition of 15 wt.% Cr – 2 wt.% Mo Cast Iron with Boron Addition

Abstract The article is aimed at the study of structural features and phase chemical composition in 3.6 wt.% C-15 wt.% Cr-2 wt.% Mo cast iron prepared with adding 0.50 wt.% boron. The work was fulfilled using optical and electron scanning microscopy, EDS, XRD, hardness measurement, and thermodynamic modelling. It was found that due to boron effect the cast iron acquired hypereutectic structure consisting of the primary M7C3 carbides (5.3 vol. %) and the eutectics based on M7C3 carbide (rosette-shaped cells) and M3C carbide (coarse-net-shaped cells or Ledeburite-shaped cells). The total amount of carbide phases was 51.8 vol.% whereas the volume fractions of M7C3-eutectic cells and M3C-eutectic cells were 21.0 vol.% and 74.7 vol.% respectively. The matrix comprised austenite, martensite and pearlite whereas austenite volume fraction was measured as 32 vol.%. Chromium and molybdenum were unevenly partitioned in phases performing the opposite character of a distribution. The primary carbides contained about 37 wt.% Cr and 1.6 wt.% Mo with the stoichiometry of (Fe3.88Cr2.76Mo0.22Mn0.12Si0.02)C3. Substantial part of carbide precipitates (primary and eutectic both) exhibited the duplex nature presenting Cr-rich/Mo-depleted core (M7C3 carbide) and Cr-depleted/Mo-rich shell (M3C carbide). Duplex carbides were closely adjusted to austenite + M3C eutectic cells to be the starting interface for their solidification. A minor amount of micron-sized areas with 67.5 wt.% Mo and 4.6 wt.% Si were observed to be presumed as M6C carbide. The cast iron was subjected to holding at 950 °C for 2 hours with subsequent oil-quenching. This treatment caused the precipitation of fine secondary carbides followed by the martensite transformation which resulted in significant hardness increase from 672 HV (as-cast) to 1038 HV. The solidification sequence is discussed in terms of structure observation and Thermo-Calc modelling.

Alloying effect on solidification behaviour and grain refinement in Ti45Al2Nb2Ta0.8B and Ti45Al2Nb2Hf0.8B

The solidification process of Ti45Al2Nb2Ta0.8B (B4522Ta) and Ti45Al2Nb2Hf0.8B (B4522Hf) Bridgman samples were studied through directional solidification. Boron addition at 0.8 at. % was found to have changed the orientation relationship of peritectic α with β dendrites. The peritectic alpha is randomly oriented in both B4522Ta and B4522Hf, it was likely to be inoculated by boride precipitates at the β/liquid interfaces during peritectic transformation. The alloying effect of Ta and Hf on the peritectic reaction was similar. Borides precipitated earlier in Ta-containing alloy than that in Hf-containing alloy during solidification.

Borocarbide coarsening and the effect of borocarbide particle size on Charpy V-notch impact properties of medium-carbon boron-containing steel

Abstract Boron-added steel has been used in several automotive components in which the energy absorbed in impact testing is an important requirement. Previous thermodynamic studies have shown that boron addition promotes significant change in equilibrium phases, increasing the volume fraction of precipitated phases, mostly due to increased carbide stability and formation of borocarbides. As volume fraction, size and distribution of precipitates influence the absorbed energy in impact testing of steels, it is important to study M23(B,C)6 borocarbide precipitation and coarsening kinetics and its effects on Charpy V-notch absorbed energy of boron steels. In the present work, borocarbide coarsening kinetics were evaluated using optical microscopy in samples heat-treated at 880 0C for different times. The borocarbide coarsening kinetics data suggest that growth is controlled by an interfacial reaction mechanism. The Charpy V-notch absorbed energy decreases with increasing borocarbide section size and the embrittlement was successfully described by an empirical equation.

Borocarbide coarsening and the effect of borocarbide particle size on Charpy V-notch impact properties of medium-carbon boron-containing steel

Abstract Boron-added steel has been used in several automotive components in which the energy absorbed in impact testing is an important requirement. Previous thermodynamic studies have shown that boron addition promotes significant change in equilibrium phases, increasing the volume fraction of precipitated phases, mostly due to increased carbide stability and formation of borocarbides. As volume fraction, size and distribution of precipitates influence the absorbed energy in impact testing of steels, it is important to study M23(B,C)6 borocarbide precipitation and coarsening kinetics and its effects on Charpy V-notch absorbed energy of boron steels. In the present work, borocarbide coarsening kinetics were evaluated using optical microscopy in samples heat-treated at 880 0C for different times. The borocarbide coarsening kinetics data suggest that growth is controlled by an interfacial reaction mechanism. The Charpy V-notch absorbed energy decreases with increasing borocarbide section size and the embrittlement was successfully described by an empirical equation.

Safety Assessments of Nickel Boride Nanoparticles on the Human Pulmonary Alveolar Cells by Using Cell Viability and Gene Expression Analyses.

Nickel boride is generally used in the steel industry as a melting accelerator due to its feature of creating a protective and stable attribute at high temperatures. It is also used to improve the hardenability of the steel with boron addition in the production. Thus, safety studies and biocompatibility analysis of nickel boride should be performed comprehensively to understand the limitations of use in various areas. In the present study, nickel boride nanoparticles (Ni2B NPs) were synthesized by a single-step method and molecule characterizations were performed via the use of X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analyses. Cytotoxicity properties of Ni2B NPs were identified on human pulmonary alveolar epithelial cells (HPAEpiC) by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red (NR), and lactate dehydrogenase (LDH) assays. Illumina human ht-12 v4.0 whole-genome microarray analysis was conducted to investigate NiB2 NPs effects on gene expression regulations of HPAEpiC cells. The database for annotation, visualization, and integrated discovery (DAVID) analysis was performed to reveal the relationship between Ni2B NP application and cellular pathway alterations. According to cytotoxicity analysis, the IC50 value for Ni2B NP application was found as 81.99mg/L concentration. Microarray analysis of Ni2B NP application was shown for the first time that 693 gene expression changes (FC ≥ 2) occurred significantly over 40.000 gene probes and Ni2B NPs were observed to affect microtubule regulation, centrosome organization, and phosphoprotein synthesis.