High-boron Alloy Research Articles

Strain-stiffening of chemical bonding enhance strength and fracture toughness of the interface of Fe2B/Fe in situ composite

Fe2B was widely used as the strengthening phase and wear-resistant skeleton in high boron iron-based composite. The weak interfacial bonding of Fe2B/Fe interface is one of the main reasons for the poor mechanical properties of the composite, which motivated us to develop a strain stiffening strategy of interfacial chemical bonds to improve the bond strength and elongation of the interface. The effects of alloying elements Ti, Cr, Mn, Co, Ni, Cu, Y, Nb, Mo, Ta, and W on Fe(001)/Fe2B(001) interface were investigated through first-principles calculations. The interface segregation energy and the work of adhesion showed that Ti, Cr, Mn, Ni, Y, Mo, Ta, and W can segregate at this interface, and the alloying elements Cr, Mn, Ni, Nb, Mo, Ta and W increase the interface bonding strength. The fracture mechanism of the interface resulted from the breaking of the FeFe bond of the bcc-Fe end near the interface. The alloying elements Cr, Mn, and Ni improved the ultimate strength and elongation of bcc-Fe(001)/Fe2B(001) interface. CrB bond displays the obvious strain stiffening in the interface. Therefore, it provides new thought and method for the design of new high boron alloys.

Ti-rich carboborides in the multi-component high-boron alloy: morphology and elemental distribution

In the article, the characterization of the morphology, chemical composition, and elemental distribution in the Ti-based carboboride M(C,B) in (wt.%) Fe-0.72C-2.75B-5.05W-5.57Mo-10.35Cr-2.60Ti multi-component alloy is fulfilled. The study was performed using optical microscopy, SEM, TEM, and energy-dispersive X-ray spectroscopy. It was found that the carboboride M(C,B) is present in the structure in the form of the equiaxed polygonal particles of a 0.5-7.3 mm mean size. The particles are divided into “duplex” and “uniform” ones. The duplex particles consists of the Ti-rich (75 wt. % Ti) “core” (Ti(C,B)) and the Ti-depleted (47.3 wt. % Ti) “shell” ((Ti,W,Mo,V)(C,B)). The uniform particles are characterized by an even distribution of the elements having a chemical composition close to the “shell”. The ratio of B:C (at. %) is 1:2.5, 1:3.3, and 1:3.2 for the “core”, “shell” and the uniform particle respectively. The chemical formulas of the duplex/uniform M(C,B) inclusions and the mechanism of their formation are proposed.

Effect of Boron on the Microstructure, Superplastic Behavior, and Mechanical Properties of Ti-4Al-3Mo-1V Alloy.

The decrease of superplastic forming temperature and improvement of post-forming mechanical properties are important issues for titanium-based alloys. Ultrafine-grained and homogeneous microstructure are required to improve both processing and mechanical properties. This study focuses on the influence of 0.01-2 wt.% B (boron) on the microstructure and properties of Ti-4Al-3Mo-1V (wt.%) alloys. The microstructure evolution, superplasticity, and room temperature mechanical properties of boron-free and boron-modified alloys were investigated using light optical microscopy, scanning electron microscopy, electron backscatter diffraction, X-ray diffraction analysis, and uniaxial tensile tests. A trace addition of 0.01 to 0.1 wt.% B significantly refined prior β-grains and improved superplasticity. Alloys with minor B and B-free alloy exhibited similar superplastic elongations of 400-1000% in a temperature range of 700-875 °C and strain rate sensitivity coefficient m of 0.4-0.5. Along with this, a trace boron addition provided a stable flow and effectively reduced flow stress values, especially at low temperatures, that was explained by the acceleration of the recrystallization and globularization of the microstructure at the initial stage of superplastic deformation. Recrystallization-induced decrease in yield strength from 770 MPa to 680 MPa was observed with an increase in boron content from 0 to 0.1%. Post-forming heat treatment, including quenching and ageing, increased strength characteristics of the alloys with 0.01 and 0.1% boron by 90-140 MPa and insignificantly decreased ductility. Alloys with 1-2% B exhibited an opposite behavior. For the high-boron alloys, the refinement effect of the prior β-grains was not detected. A high fraction of borides of ~5-11% deteriorated the superplastic properties and drastically decreased ductility at room temperature. The alloy with 2% B demonstrated non-superplastic behavior and low level of strength properties; meanwhile, the alloy with 1% B exhibited superplasticity at 875 °C with elongation of ~500%, post-forming yield strength of 830 MPa, and ultimate tensile strength of 1020 MPa at room temperature. The differences between minor boron and high boron influence on the grain structure and properties were discussed and the mechanisms of the boron influence were suggested.

The Effect of Microstructure Size on Microstructure and Properties of High Boron Alloy During Quenching and Partitioning (Q&P) Process

The Effect of Microstructure Size on Microstructure and Properties of High Boron Alloy During Quenching and Partitioning (Q&P) Process

Current Functional Materials for Wear-Resistant Casting: from Multicomponent Cast Irons to Hybrid High-Boron Alloys

Current Functional Materials for Wear-Resistant Casting: from Multicomponent Cast Irons to Hybrid High-Boron Alloys

Influence of changes in alloying elements distribution and retained Austenite (RA) on mechanical properties of high boron alloy during quenching and partitioning(Q&P) process

The quenching and partitioning (Q&P) process has been adopted innovatively to improve the toughness and wear resistance of Fe-0.44C-1.54B-3.97Mn-0.79Al-0.95Si alloy, and the microstructure, distribution of alloying elements, mechanical properties and dry sliding wear behavior of this alloy in as-cast and heat-treated by Q&P process were systematically investigated. The results show that test alloy consists mainly of martensite, retained austenite (RA) and eutectic boride phases. After being treated by Q&P process, the distribution of alloying elements in the microstructure becomes uniform and the impact toughness increases from 4.02 J cm-2 to 6.82 J cm-2, while the mass loss of the alloy is also decreased from 0.064 g to 0.051 g in dry sliding wear test. The improvement of the mechanical properties is attributed to the changes in the during Q&P process, especially the increase in the volume fraction of thin-film RA, as well as the fracture and spheroidization of part of the net-like boride.

Study on 2.0 wt.% B Dual-Phase Stainless Steels of Different Ferrite/Austenite Ratios

High boron duplex stainless steels (containing 2.0 wt.% B) of different ferrite/austenite ratios were fabricated by vacuum arc melting technique. To improve the morphology and distribution of the borides in the high boron alloys, hot rolling was carried out on these samples. Borides have a size about 20 μm and they present slender and blocky shape in the solution treated samples. After hot rolling, the slender borides transform to isolated blocks with a size below 10 μm. The hot-rolled sample has the highest elongation of 10.6 ± 0.7% when it consists of 29.6 ± 2.7% ferrite, 48.7 ± 3.5% austenite and 21.5 ± 2.3% boride, with the yield strength and ultimate tensile strength of 525 ± 12 MPa and 841 ± 10 MPa, respectively. Its corrosion resistance in 3.5 wt.% NaCl solution is in the same level as 304 stainless steel.

A comparative study of high boron alloys with 2.0 wt% B based on 304 and 316 stainless steels

High boron alloys containing 2.0 wt% B based on 304 and 316 stainless steels, respectively, were prepared by vacuum arc melting method. Hot rolling was conducted to measure the workability of the two types of high boron alloys. M2B borides of long stripy and blocky shape are presented randomly over the matrix in the as-cast alloy based on 304 stainless steel. In addition to the M2B borides, Mo-rich M3B2 borides are formed and they promote the connectivity of the borides in the as-cast alloy based on 316 stainless steel. The alloy based on 304 stainless steel has well hot workability, whereas the alloy based on 316 stainless steel was severely cracked during the hot rolling process.

Effect of boron on isothermal oxidation behavior of a nickel-base superalloy with high Al and Ti contents

The influence of boron on the oxidation resistance of conventionally cast U720Li alloy was investigated at 1130 °C and analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and electron probe microanalysis (EPMA). It has been found that the boron-undoped and -doped alloys all obey a super-parabolic rate law, but the oxidation rate is obviously increased by the boron addition. These alloys all show non-uniform oxidation between dendritic and interdendritic areas due to the serious microsegregation, while the oxide scale morphology of the high-boron alloy is quite different from that of the boron-undoped alloy. For boron-doped alloys, in the initial stage of oxidation the outward diffusion of boron from borides formed in the interdendritic region results in the formation of discontinuous and non-uniform B-rich oxide layers beneath and inside the Cr2O3 layer, while as the oxidation proceeds further boron can also transfer from the B-rich oxide to outer layers which eventually leads to disappearance of the B-rich oxide layers. The formation of B-rich oxide layers destroys the continuity of Cr2O3 layer and decomposition of B-rich oxide layers makes Cr2O3 layer more porous, which significantly reduce the protective property of the Cr2O3 layer and in turn decrease the oxidation resistance. Moreover, the eutectic (γ + γ′) highly enriched in Ti, Al is prone to be oxidized and form a thicker scale than the other regions, and hence the significant increase of its precipitation with boron addition also contributes to increasing the oxidation rate.

Study on the nucleation mechanism of hard particles in high boron and high carbon alloy by laser-induced arc welding

It is an effort to improve the phenomenon of thick boron-carbon compound forming, during the process of arc surfacing of high boron and high carbon alloy. This paper deals with the refinement of hard particles, in order to improve the microstructure of the surfacing layer. The comparison of microstructure and hard particles composition between laser arc composite surfacing layer and arc surfacing layer confirmed that hard particles of both are (Fe, Cr)7(B, C)3 and (Fe, Cr)2B. Also, the results show that in the cross section of the arc surfacing layer, the hard particles are in the shape of long strips, hexagonal and regular quadrangular blocks. But the size of hard particles decreases and follows a uniform distribution under laser induction. The wear resistance of laser arc composite surfacing layer is obviously improved. This may be due to that thick hard particles were broken into smaller units by pulsed laser stirring molten pool, thus providing more nucleating particles for the formation of hard particles. At the same time, the thick hard particles were melt down by high energy laser beam, which improves the temperature gradient and forces hard particles to grow uniformly.

Microstructures and high-temperature mechanical properties of a directionally solidified Ni-based superalloy: Influence of boron content

The effects of boron content on the microstructure and mechanical properties of a directionally solidified Ni-based superalloy were investigated. The increase of boron content significantly increases the amount of γ/γ′ eutectic, impels the formation of multi-phase eutectic-like constituent, and promotes the morphological transformation of MC carbides from rod-like to blocky. After standard heat treatment, the incipient melting occurs in the high boron alloy, which can lower the dissolving temperature of γ/γ′ eutectic. With increasing boron content, the volume fraction of secondary γ′ phase decreases significantly and the homogeneity and alignment of secondary γ′ show a decrease, and the tensile strengths at 900 °C decrease slightly mainly due to the strengthening effect of much more tertiary γ′ phases. The wide γ matrix channel facilitates the movement of dislocations, which is somewhat beneficial to the elongation, while the incipiently melted region (IMR), the decreased volume fraction of secondary γ′ phase and the less homogeneity of secondary γ′ phase are rather harmful to the elongation. Consequently, the elongation is drastically reduced. The existence of a large amount of IMRs is principally responsible for the reduction of the stress rupture property. Tertiary γ′ phases re-dissolving in γ matrix channel facilitates the movement of dislocations between large secondary γ′ phases, which is beneficial to the elongation of the alloys. In addition, the IMRs provide masses of crack sources, and consume the precipitation strengthening elements (Ti, Ta) and the solid solution strengthening elements (Cr, W and Mo), which plays the major role in the degradation of the high-temperature tensile or stress rupture properties.

Effect of Cu on microstructure, crystallography and mechanical properties in Fe-B-C-Cu alloys

In order to improve the hardenability and toughness of high boron alloys, XCu (X = 0, 0.5, 1, 1.5, 2, 3, weight %) were added into high boron alloys. The Cu precipitation behavior and its effect on hardenability, microstructure, crystallography and mechanical properties of as-cast Fe-B-C-Cu alloys have been investigated systematically by means of SEM, XRD, TEM, EPMA and EBSD. The results indicate that Cu improves the hardenability of Fe-B-C-Cu alloys, while excessive Cu atoms segregating at the matrix attaching to boride promote the appearing of nano-Cu precipitation with body-centred cubic (bcc)structure, which can act as heterogeneous nuclei of the pearlite, leading to the reduction of hardenability. Therefore, the Cu concentration in Fe-B-C-Cu alloys should be controlled below 2wt%. Observation of TEM reveals that the orientation relationship(OR) between martensite and retained austenite are [001]α // [011]γ and [110] α//[1(−)1(−)1] γ. As well, the OR between ferrite and M3C are (100)M// (010)M3C and [011]M//[001]M3C. EBSD analysis shows that the misorientation angles of the α-Fe and M2B phases are mainly low-angle with less than 5°. The α-Fe phase has the preferred crystal plane (111) // ND-type grain, while the M2B phase displays a preferred growth orientation [002] on the M2B crystal plane (001). A possible OR between borides and α-Fe in Fe-B-C-Cu alloys is (001)α-Fe //(001)M2B. In addition, the bulk hardness and impact toughness increase obviously with 1–2wt% copper concentration owing to the increasing of volume fraction of martensite(Vm), which maybe a guiding copper addition in Fe-B-C-Cu alloys.

Fabrication of cast electrodes from nanomodified nickel aluminide-based high-boron alloy to fabricate spherical powders using the plasma rotating electrode process

A complex manufacturing method of billets from material based on high-boron nickel aluminide is proposed. The method includes manufacturing the semifinished alloy products using a combined method of self-propagating high-temperature synthesis and centrifugal casting from oxide feedstock and subsequent vacuum induction remelting with the introduction of Al-based foundry alloys containing nanosized ZrO2 and modifying the structure. The evolution of the microstructure and phase composition is investigated at all production stages. A cast ZrO2-modified cylindrical billet, which possess high purity in regards to gas impurities (O 0.005 wt % and N 0.0001 wt %) and is suitable for the further production of powders by the plasma rotating electrode process, is fabricated according to the proposed technology.

Fabrication of Cast Electrodes from Nanomodified Nickel Aluminide-Based High-Boron Alloy to Fabricate Spherical Powders Using the Plasma Rotating Electrode Process

A complex manufacturing method of the billets from the material based on high-boron nickel aluminide is proposed. The method includes manufacturing the semifinished alloy products using a combined method of self-propagating high-temperature synthesis and centrifugal casting from oxide feedstock and subsequent vacuum induction remelting with introducing Al-based foundry alloys containing nanosized ZrO2 and modifying the structure. The evolution of the microstructure and phase composition is investigated at all production stages. A cast ZrO2-modified cylindrical billet, which possesses high purity in regards to gas impurities (O – 0,005 wt.% and N – 0,0001 wt.%) and is suitable for the further production of powders by the plasma rotating electrode process, is fabricated according to the proposed technology.

Study on Microstructure and Property of High Boron Alloyed Stainless Steel Composite Plate Containing Titanium

A certain amount of Ti was added into high boron alloyed stainless steel with content 2.25%B, and then high boron alloyed stainless steel composite casting slab with three layers was fabricated , in which central layer is high boron alloyed stainless steel containing Ti and cladding is plain 304 stainless steel without Ti. The microstructure of core and interface and the mechanical property of the composite plate were studied after hot forged, hot rolled and solution treated process respectively. The results show that the boride in as-cast microstructure of core are (Fe,Cr)2B phase with long strip and TiB2 phase with petal shape, moreover the formation of TiB2 phase decreases the amount of (Fe,Cr)2B phase. Two kinds of boride are fully broken after hot rolling and distributed in the form of block uniformly in matrix, and TiB2 phase is more fine uniform. The mechanical property especially plastic performance of high boron alloyed stainless steel composite plate containing Ti after solution treatment is improved significantly, it has reached and surpassed the United States ASTM A887-89 delivery standards.

Analysis of Boride Phase Composition in High Boron Alloyed Stainless Steel Containing Titanium

Hard and brittle (Fe,Cr)2B phase caused by excess boron in high boron alloyed stainless steel has adverse effects on the hot working performance and mechanical properties of material. Adding Ti into high boron alloyed stainless steel can improve the type, morphology and distribution of boride phase. The results show that TiB2 phase with petals or small block shape forms after adding Ti into high boron alloyed stainless steel, and as the increase of Ti content, TiB2 phase replaces (Fe, Cr)2B gradually. Moreover, the petal-like TiB2 phase becomes smaller and more granular after high temperature deformation, and the segregation of matrix composition is significantly weakened by the formation of TiB2 phase.

Research on Mechanical Properties of High Boron Alloyed Stainless Steel Composite Plate Containing Titanium

High boron alloyed stainless steel composite plates with different Ti content by cladding casting and hot forming process were fabricated. The mechanical properties of composite plates were analyzed after solution treatment. The results show that the composite plate has optimal microstructure and properties at 1100°C solution temperature, holding for 4h.The comprehensive properties of the composite plates are improved with the increase of Ti content, but excess Ti content can lower the plasticity. The elongation and the tensile strength of composite plate reaches 29% and 527MPa respectively, the mechanical properties can meet and exceed the supply standard requirements in ASTM A887-89 of U.S. when the reasonable content of Titanium is about 5%.

Shield Performance of High Boron Alloyed Stainless Steel Composite Plate

The shield thermal neutron performance of two high boron alloyed stainless steel composite plates(HBASSCP) was studied by the method of neutron beam transmission of neutron source reactor. The testing results indicate that the shield performance of the composite material is heavily affected by the size and distribution of the boride. Although the radiationresistance of high boron alloyed stainless steel increases with boron content, but blocky and sparse hypereutectic boride will appear in matrix when boron content is high (more than 3%), and these borides are difficult to be broken during hot deformation, so the thermal neutron is easy to penetrate directly through the space and can not be absorbed effectively. The difference between the shield performance obtained from experiments and the theoretical calculation is small for HBASSCP containing hypoeutectic boride in core material, but it is great for HBASSCP containing hypereutectic boride in core material.

Effect of Titanium on Microstructure and Phase Composition of High Boron Alloyed Stainless Steel

High boron alloyed stainless steel(HBASS) with different Ti content were fabricated by vacuum induction furnace and their microstructure and boride phase were analyzed. The boride phase of HBASS do not contain Ti element is mainly (Fe,Cr)2B phase with slender rod-shape. After adding Ti into steel, because Ti and B preferentially combines into TiB2 phase with petals or small block shape which can stop the formation of hard and brittle (Fe,Cr)2B, so the number of (Fe,Cr)2B phase is reduced. And after adding Ti, many crisscross cracks appeared in internal large (Fe,Cr)2B phase, which will be effective to break into small pieces of boride to improve steel plasticity and shielding thermal neutron performance during hot rolling process.

Effect of K / Na on Primary Boride of Hypereutectic High-Boron Alloy

High-alloy materials such as high chromium cast iron and high speed steel have excellent wear resistance under extreme wear conditions. But they consume much expensive chromium, molybdenum, tungsten and other alloying elements too. The hypereutectic high boron alloy has good wear resistance because it contains many high hardness primary borides. But the dimension of primary borides is big. In this paper, the hypereutectic high boron alloy was prepared using sand casting method, and the primary borides were modified by different amount of K / Na modificator. The results show that the primary boride of hypereutectic high boron alloy is Fe2B. K/Na modificator has a significant influence on primary Fe2B. The best grain refinement effect of primary Fe2B is obtained when the amount of K/Na modificator is 0.3%. The refining mechanism of primary Fe2B is that K/Na modificators can not only increase the supercooling degree to improve nucleation rate but attach to the crystal face of fastest growth direction to prevent grain from growing