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Self-piercing riveting (SPR) has been used to join similar and dissimilar materials for vehicle body application. In order to understand the failure mechanism and develop a method to estimate the shear strength of SPR similar and dissimilar materials, finite element modeling was conducted in this study. In the modeling, the contact conditions between the rivet and the workpieces were taken into account to establish the failure criteria of SPR of steel and aluminum sheets. It was found that the failure procedure of riveted dissimilar materials was different from that of riveted similar materials. Furthermore, the experiments were conducted to validate the modeling results. It was shown that the shear strength and failure mode of SPR joints were in agreement with the modeling results. These results suggested that the model could be used to estimate the shear strength of SPR joints. The factors influencing the failure mode and shear strength of SPR joints were discussed in detail. For rivet pull-out mode, the rivet open angle at the upper sheet, friction coefficient between the rivet and sheet, and the yield strength of the substrate were the key factors. For sheet tearing mode, failure occurred at the weaker sheet and the shear strengths mainly depended on the sheet gage and strength grade of the weaker sheet. [ABSTRACT FROM AUTHOR]

The effects of silicon alloying and heat treatment on the microstructure and properties of Fe-35Cr-4C-xSi (x = 0.5, 1.2, 19, 2.6) hypereutectic high-chromium cast iron (HHCCI) were explored through first-principles calculations and phase diagram calculations combined with XRD, SEM, TEM and other methods. With the increase of Si content, the matrix structure of HHCCI transforms from martensite to ferrite. The phase diagram analysis reveals that higher silicon content results in elevated austenite transformation initiation temperatures, reduced austenite phase areas, and expanded ferrite phase regions. Additionally, the study calculates the diffusion activation energy of C atoms within silicon-bearing and silicon-free HHCCI matrices, providing valuable insights into the role of silicon in promoting the transformation of the HHCCI matrix into ferrite. Notably, silicon facilitates the diffusion of C atoms into the silicon-bearing HHCCI matrix, thereby preventing complete austenitization. After ultra-high-temperature heat treatment, the matrix structure of high-silicon HHCCI (1.9 wt.% Si) can be transformed from ferrite to martensite. With the increase of Si content, the corrosive wear resistance of HHCCI increases first and then decreases. The 1.9Si HHCCI after ultra-high-temperature heat treatment exhibits the best corrosive wear resistance in both acidic and alkaline corrosive wear environments, and the silicon-bearing HHCCI is more resistant to alkaline corrosive wear. This study reveals promising applications of silicon-bearing HHCCI in industries such as hydraulics and coal mining, particularly as a material for making slurry pumps. Notably, in comparison with previous work by our research group, this study delves deeper into the mechanisms underlying the structural and performance changes of silicon-bearing HHCCI due to heat treatment and silicon content variation. [ABSTRACT FROM AUTHOR]

The excellent hardness and wear resistance of AlCoCrFeNiMo0.8–TiC composite coating benefit from various strengthening mechanisms, including fine grain strengthening, dislocation strengthening, load transfer strengthening, solid solution strengthening, and precipitation strengthening. To analyze their contributions in the strength and hardness, an accurate prediction model is essential. In this work, a prediction model for the hardness increment was established based on some key elastic constants calculated by the first-principles. Subsequently, the contributions of strengthening mechanisms were quantitatively evaluated by the developed prediction model. It was found that the Young's modulus and shear modulus for B2 phase were 179.65 GPa and 67.36 GPa, respectively, and those of σ phase were 354.08 GPa and 139.19 GPa, respectively. The precipitation strengthening was the predominant mechanism in the composite coating, with a strength contribution of 736.4 MPa and a hardness contribution of 225.2 HV, which accounted for 76.2% of the contribution values. The prediction model has high accuracy, which is evidenced by the small relative error (9.1%) between the total theoretical hardness contribution (295.2 HV) and the Vickers hardness tested by nanoindentation (322.1 HV). The AlCoCrFeNiMo0.8–TiC composite coating has various strengthening mechanisms. To quantitatively analyze these contributions on the hardness, a prediction model is established based on the elastic moduli obtained by the first-principles calculations. [ABSTRACT FROM AUTHOR]

The effect of Si on the microstructure and properties of hypereutectic high-chromium cast iron was investigated. The results show that Si is only solid-dissolved in the matrix, and the content of Si is higher in the matrix near the edge of the primary carbide. As the Si content increased from 0.5 to 2.6%, the primary carbides in hypereutectic high-chromium cast iron were significantly refined, and the refining mechanism was verified by first-principles calculations. The increase of silicon content also leads to the increase of carbide volume fraction from 52.4 to 63.9%, the decrease of austenite volume fraction from 45.8 to 2.0%, and the matrix structure gradually transforms from γ-Fe to α-Fe. After hypereutectic high-chromium cast iron was quenched at 1050 °C, a large amount of secondary carbides were precipitated in the matrix and the precipitation of secondary carbides decreased significantly with the increase of silicon content. After quenching at 1050 °C, the hardness of hypereutectic high-chromium cast iron increased significantly, but the hardness of high-silicon (1.9Si and 2.6Si) samples did not change significantly. Increasing the quenching temperature and prolonging the holding time can significantly improve the hardness of high-silicon samples. The increase of silicon content can significantly improve the wear resistance of hypereutectic high-chromium cast iron. When the silicon content exceeds 1.9%, the wear resistance decreases. [ABSTRACT FROM AUTHOR]

In order to solve the problems of low hardness and poor wear resistance of titanium alloy, laser cladding technology was used to prepare NiCrBSi coatings with different amounts of B4C on the surface of Ti-6Al-4V alloy. The effects of B4C content on the microstructure evolution, hardness, fracture toughness, and wear resistance of NiCrBSi coatings were investigated. The results showed that with an increase of B4C addition, the size and number of ceramic phases TiB2, TiC, and CrB in the coating increased, and the ceramic phases were dispersed in the coating. The average microhardness of the coating with 9 wt.% B4C addition was the highest, reaching 1250.3 HV0.2, which is 15% higher than that of the coating without B4C addition. After adding B4C, the fracture toughness of the coating increased. When the addition of B4C was 3 wt.%, the fracture toughness of the coating was the highest, reaching 1.42 MPa m1/2, which is 178.4% higher than that of the coating without B4C. With the increase of the addition of B4C, the wear loss of the coating decreased and the wear resistance increased. [ABSTRACT FROM AUTHOR]

The carbide precipitation behavior of 35 wt%Cr–4 wt%C (35Cr–4C) Hypereutectic High Chromium Cast Iron (HHCCI) during heat treatment was investigated by means of scanning electron microscope and transmission electron microscope, and the effect of rare earth magnesium (RE-Mg) modification on the microstructure evolution and wear resistance of 35Cr–4C cast iron was also studied. The as-cast structure of 35Cr–4C HHCCI is mainly composed of primary carbides, eutectic carbides and austenite matrix. After quenching, there are secondary carbides M7C3 and M23C6 precipitation in the martensite matrix. After tempering, more secondary carbides will be formed and the main precipitate phase is M23C6. After heat treatment of RE-Mg modified HHCCI, more secondary carbides are precipitated, and the distribution in the matrix is more uniform, and the wear resistance is higher than that of unmodified HHCCI. [ABSTRACT FROM AUTHOR]

The effects of different partitioning temperatures and time on the microstructure and properties of Mn-Si-Cr alloy steel were investigated. The results showed that with the increase in the partitioning temperature or the extension of the partitioning time, the martensite arrangement in the Mn-Si-Cr alloy steel became irregular, and the boundary was gradually blurred; the austenite mainly existed in the form of thin film, and the austenite content increased at first and then decreased gradually. When the partitioning temperature was too high or the partitioning time was too long, all led to the decomposition of austenite into low-carbon bainite and carbides. With the increase in the temperature, the hardness of the samples decreased gradually, the wear weight loss increased gradually, and the impact toughness increased linearly. With the extension of the partitioning time, the hardness of the sample gradually decreased. When the partitioning time is 5-10min, the hardness decreases greatly. When the partitioning temperature was 350 °C and the partitioning time was 60s, the test steel can have hardness, impact toughness, and wear resistance and has good comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

The zirconium alloy cladding tube and end plug used for nuclear fuel rods are usually joined by pressure resistance welding. And the service performance of the fuel rod cladding is directly influenced by the welded joint. In order to understand the forming process deeply, an axisymmetric electro-thermal–mechanical process finite element model was established in this paper. The current density distribution, temperature field evolution, and joint forming process during pressure resistance welding were all simulated by this model. It was shown that due to the contact resistance, a concentrated heat flow was rapidly generated on the tube-plug contact surface caused by welding current. A heat conduction was established on both sides of the welding surface. The high-temperature region on the side of the cladding tube was larger than the end plug. The metal of the tube extruded to both inside and outside of the joint under the coupled loading of heat and pressure. The location of the highest instant temperature on the welding surface moved from the inside to the outside of the joint. The highest temperature was 1568 °C, not reaching the melting point of zirconium alloy. The joining area and the highest temperature increased with welding current increasing, the welding time had little effect on them. Based on the numerical model, two structural design schemes to improve the joint forming quality were proposed. They were expected to provide a guide line for the joint design. [ABSTRACT FROM AUTHOR]

A dense Cu-10Sn alloy bulk specimen was obtained by optimizing the laser powder bed fusion (L-PBF) processing, and the relative density of the specimen reached 99.7%. The grain morphology was mainly the columnar dendrite and inter-dendritic phases generated along the solidification direction. Tensile testing and detailed microstructural characterization were carried out on specimens in the as-built and heat-treated condition. Under the quasi-static tensile condition, the yield strength (σ0.2), ultimate tensile strength (UTS), and the elongation of the as-built Cu-10Sn specimen were 392 MPa, 749 MPa and 29%, respectively. After the solution treatment at 800 °C for 4 h, and aging treatment at 400 °C for 2 hours, the microstructure of the specimen transformed from the columnar grain to equiaxed grain, the dislocation density decrease, and numerous annealing twins were observed in the heat-treated state. Therefore, the quasi-static tensile yield strength (σ0.2) of the specimen was reduced to 245 MPa. However, the UTS and the elongation were increased to 840 MPa and 56%, respectively, due to the interaction between annealing twins and equiaxed grain. [ABSTRACT FROM AUTHOR]

In this study, a Hastelloy X alloy single track was manufactured by means of selective laser melting. The transient temperature field and cooling rate characteristics of single tracks in the manufacturing process were simulated using the ABAQUS software. The cross-comprehensive effects of the scanning speed and power of the selective laser melting process on the surface morphology, geometric characteristics, wetting and spreadability of single tracks were analyzed. The results indicated that the transient peak temperature and average cooling rate decreased with the increase in scanning speed, but increased with the increase in laser power. At the same time, the height and width of the single track gradually increased in conjunction with the laser power and decreased with increased scanning speed. A two-factor variance analysis indicated that the contribution rates of laser power and scanning speed to the geometric size of the single tracks were 89.02% and 10.25%, respectively. Therefore, optimization of the laser's power control exerts a higher process effect on single track formation quality. [ABSTRACT FROM AUTHOR]

This work aims to elucidate the microstructure characteristics of each phase in carbidic austempered ductile iron and the nucleation and growth of acicular ferrite in an austempering temperature range of 250–450 °C. The research results showed that the carbides (Fe, Cr)3C obtained by the eutectic reaction had high indentation hardness and indentation modulus, and the interface between acicular ferrite and eutectic carbides belonged to incoherent boundary. Since the nucleation driving force of acicular ferrite increased with an increase in temperature difference (ΔT), the size of acicular ferrite gradually decreased with the decrease in isothermal temperature. When the austempering temperature was above 400 °C, acicular ferrite preferentially nucleated around the graphite nodules and inside grains. However, acicular ferrite preferentially nucleated around the graphite nodules and the eutectic carbides at temperature below 400 °C. Additionally, a fine twin structure had been found inside some acicular ferrite after austempering at a low temperature (250 °C). [ABSTRACT FROM AUTHOR]

Through the heat treatment of 0.8Cr–2.2Mn–0.3Mo–1.0Si–0.004B–0.45C (wt%) bainitic steel (i.e., 45Mn2 bainitic steel), the influence of different heat treatment parameters on microstructure evolution and mechanical properties of 45Mn2 bainitic steel was studied. Optical microscope, Scanning electron microscope, X-ray diffraction, hardness testing and abrasion testing were used for analysis. The results show that the microstructure of 45Mn2 bainitic steel after quenching is lower bainitic ferrite + residual austenite + M/A. When the austenitizing temperature increases, the volume fraction of residual austenite and M/A increases, and the hardness and abrasion resistance first increase and then decrease. At 910 °C, the hardness is the highest, while the wear resistance is the best. After quenching at 910 °C and different tempering temperatures, it is found that the microstructure has no obvious change, and the hardness and wear resistance are the highest when tempered at 240 °C. [ABSTRACT FROM AUTHOR]

In this paper, the effects of xGe (x = 0, 0.002, 0.005, 0.01%) on the melting point, spreadability, wettability, microstructure, and mechanical properties of Sn-32Pb-18Cd solder alloys were investigated. The experiment results showed that the addition of Ge could increase the spreading area and wetting properties. The microstructures of solder alloy after reflowing were mainly composed of Pb phase and β-Sn phases, and the Cd element was distributed in the matrix. The addition of Ge could enhance the tensile strength and ductility. When the Ge content was equal to 0.005%, the maximum elongation reached 53.70%. [ABSTRACT FROM AUTHOR]

The effect of austenitizing temperatures at 850, 880, 910, 940, 970 and 1000 °C, respectively, and tempering at 250 °C on the microstructure, mechanical properties, strengthening and toughening mechanism, and wear behavior of Si-Mn-Mo cast steel containing 0.45%C-2.0%Si-1.0%Mn-0.3%Mo-0.8%Cr-0.004%B were systematically investigated. The results indicated that the microstructure of water quenching Si-Mn-Mo cast steel was mainly composed of lenticular martensite, martensite/austenite, bainitic ferrite and retained austenite. After tempering, the homogeneity of the microstructure improved. As the austenitizing temperature increased, the hardness of the steel increased first, and then it remained almost constant, the impact toughness decreased significantly, and the wear loss decreased first and then increased. Under low wear load, the steel austenitizing at 910 °C had excellent wear resistance before and after tempering. Under high wear load, after tempering, the steel austenitizing at 850 °C had the optimum wear resistance. The wear mechanisms were mainly abrasive wear, oxidation wear and adhesive wear. [ABSTRACT FROM AUTHOR]

The influence of the austempering process on microstructure evolution, mechanical properties, wear resistance, and corrosion resistance of Cu-bearing carbidic austempered ductile iron (CADI) was investigated. The results show that with an increase in the austempering temperature, the amount of acicular ferrite decreases, the volume fraction and carbon content of retained austenite increase gradually, the hardness and tensile strength decrease, and the impact toughness and corrosion resistance increase. Wear tests show that as the austempering temperature increases, the wear resistance of Cu-bearing CADI is improved and decreases when the temperature exceeds 300 °C. Comparing to the conventional single-step austempering process, two-step austempering process (namely added pre-quenching at 260 °C) significantly improves the wear resistance of Cu-bearing CADI by more than 16% without compromising toughness. [ABSTRACT FROM AUTHOR]

Microstructure and properties of the alloys could be changed by heat treatment process. In this work, effect of quenching temperature on the microstructure of Al-bearing high-boron high-speed steel (AB-HSS) was investigated by means of optical microscopy, scanning electron microscopy and X-ray diffraction. Hardness and wear resistance of AB-HSS at different quenching temperatures were tested by rockwell hardness tester, microhardness tester and wear tester, respectively. The experimental results indicate that the microstructure of as-cast AB-HSS is mainly composed of pearlite, ferrite, M2B-type boride and M23(C, B)6-type borocarbide. After quenched treatment, the matrix transforms into the martensite and the type of boride has no obvious change. The morphology of boride changes from continuous network and fish-bone to isolate shape and granular distribution. As quenching temperature increases, the hardness of alloy increases. The hardness reaches 65.1 HRC when quenching temperature is 1110 °C. The wear resistance of alloy gradually increases with the increase in quenching temperature. The wear resistance is the best when the quenching temperature reaches 1110 °C. [ABSTRACT FROM AUTHOR]

The effects of chromium content on microstructure, hardness and wear resistance of as-cast Fe-xCr-1.0B (x = 0, 4, 8, 12, 16, 20) alloys were investigated by means of optical microscope (OM), scanning electron microscope (SEM), x-ray diffractometer (XRD), hardness tester and ring block wear tester. The results showed that the microstructures of chromium-free alloy were mainly composed of pearlite, ferrite, and eutectic borocarbides, and the hardness was very low, only 18.8 HRC. With the increase in chromium content, the matrix of as-cast Fe-Cr-B alloy gradually began to transform from pearlite and ferrite to lath martensite, and the type of borocarbides changed from Fe2(B, C) to M2(B, C), M7(C, B)3 and M23(C, B)6 (M = Fe, Cr). When the chromium content was 12 wt.%, the hardness of alloy reached the highest value of 61.1 HRC, and the wear resistance of alloy was the best. The results of worn surface analysis showed that the wear failure of as-cast Fe-Cr-B alloy was mainly caused by multiple plastic deformation and micro-cutting. [ABSTRACT FROM AUTHOR]

The microstructure, hardness and sliding wear behavior of bainitic steel containing 1.0–2.5% Si were investigated by means of the optical microscope, the scanning electron microscope, the X-ray diffraction, energy-dispersive spectroscopy, Rockwell hardness tester, microhardness tester and M-200 wear tester. The results show that the as-cast structure is mainly composed of acicular lower bainite and retained austenite. As the silicon content increases, the bainitic lath is refined, the retained austenite content is reduced, and the hardness tends to increase. After normalizing at 900 °C, the microstructure of the steel is mainly acicular lower bainite and film-like retained austenite. With the increase in Si content, the bainite needle is more refined, the retained austenite content is reduced, and the hardness is increased by about 20%. In as-cast and normalizing condition, as the silicon content increases, the wear loss of cast steel is reduced, and the wear resistance is improved. The wear loss of normalizing steel is obviously smaller than that of as-cast steel. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of titanium modification on microstructures and properties of carbidic austempered ductile iron (CADI) containing 3.72 wt.% C, 2.77 wt.% Si, and 0.51 wt.% Mn. The results showed that with the addition of 0.1 wt.% Ti, TiC particles were formed, and distributed in carbides and matrix. Microstructural observation indicated that the maximum diameter of graphite nodules decreased from 58 to 40 μm, and the shape of carbides transformed from network to fragmentation, which was related to the nucleation of the eutectic structure (γ + (Fe, Cr)3C) where TiC particles act as the nucleus. After isothermal quenching at 300 °C, the hardness of Ti-bearing CADI was 3.5 HRC higher than ordinary CADI, and the impact toughness was increased by 14.3%. Additionally, due to the decrease in exfoliation, the wear loss of Ti-bearing CADI was 14.8% lower than ordinary CADI during the block-on-ring wear test at the surface load of 300 N. [ABSTRACT FROM AUTHOR]

The effects of aluminum content on the morphology of eutectic borocarbide and temper softening resistance of high-boron high-speed steel with 2.0 wt pct B-0.4 wt pct C-6.0 wt pct Cr-4.0 wt pct Mo-x wt pct Al-1.0 wt pct Si-1.0 wt pct V-0.5 wt pct Mn (x = 0.0, 1.0, 1.5, 2.0) have been investigated in the present work. The experimental results indicate that aluminum not only promotes the refining and nodulizing of borocarbide, but also improves the red-hardness of the alloy. The as-cast microstructure of high-boron high-speed steel (with different aluminum contents) consists of matrix α-Fe, eutectic borocarbide M2(B,C), and boron-cementite M3(B,C) (M = Fe, Cr, Mo, V, Mn). Borocarbide presents a continuous network structure in the microstructure of alloy without aluminum addition. With increasing aluminum content, borocarbide is spheroidized, and its size decreases. Furthermore, the variation in aluminum content barely affects the phase type. The hardness testing results of heat-treated samples at 1050 °C, 1100 °C, and 1150 °C reveal that the quenching temperature for obtaining the martensite matrix rises with an increase of aluminum content. However, the alloy matrix with 2.0 wt pct aluminum cannot transform to a martensite matrix through quenching, even at 1150 °C. The red-hardness is defined as the alloy hardness after four rounds of tempering at 600 °C for 1 hour. The hardness of alloy without aluminum addition reduces significantly after tempering, while the hardness of alloy with 1.0 wt pct aluminum exhibited the highest value. Moreover, no apparent change in borocarbide morphology occurred after tempering, indicating that the alloy microstructure renders good tempering stability. [ABSTRACT FROM AUTHOR]

In this study, particle and short fiber-reinforced titanium matrix composite coatings are prepared via laser in situ technique using (0.5 and 50 μm) TiB2 and Ti powder as cladding materials. The microstructure and properties of the composite coatings are studied, and the changing mechanism of the microstructure is discussed. The results reveal that particle agglomeration is prone to appear with using fine TiB2 particles. Decomposition of the particles preferentially occurs with using coarse TiB2 particles. The cracks and pores on the surface of the coating are formed at a lower laser energy density. With the increase in the laser energy density, cracking on the surface of the coating diminishes, but the coating exhibits depression behavior. The depression extent of the coating using fine TiB2 particle as the reinforcement is much less than that of the coating using coarse TiB2 particle. Moreover, the size of the aggregate and the tendency of cracking can be reduced with the increase in Ti addition. Meanwhile, short TiB fiber bundles are formed by the diffusion mechanism of rod aggregate, and randomly oriented TiB short fibers are formed mainly by the dissolution-precipitation mechanism of fine TiB2 particles. Moreover, the growth of short TiB fibers can be in an alternating manner between B27 and Bf structures. The micro-hardness and wear resistance of the coatings are evidently higher than that of the titanium alloy substrate. The wear resistance of the large size TiB2 coating is higher than that of the small size TiB2 coating under the condition of low load. [ABSTRACT FROM AUTHOR]

In surface mount technology, the Sn-3.0Ag-0.5Cu solder joint has a shorter impact lifetime than a traditional lead-tin solder joint. In order to improve the impact property of SnAgCu lead-free solder joints and identify the effect of silver content on tensile strength and impact property, impact experiments were conducted at various strain rates on three selected SnAgCu based solder joints. It was found that joint failure mainly occurred in the solder material with large plastic deformation under low strain rate, while joint failure occurred at the brittle intermetallic compound layer without any plastic deformation at a high strain rate. Joint strength increased with the silver content in SnAgCu alloys in static tensile tests, while the impact property of the solder joint decreased with increasing silver content. When the strain rate was low, plastic deformation occurred with failure and the tensile strength of the Sn-3.0Ag-0.5Cu solder joint was higher than that of Sn-0.3Ag-0.7Cu; when the strain rate was high, joint failure mainly occurred at the brittle interface layer and the Sn-0.3Ag-0.7Cu solder joint had a better impact resistance with a thinner intermetallic compound layer. [ABSTRACT FROM AUTHOR]

First principles was carried out studying the properties of (Ti, Nb)C compounds based on density functional theory. The integration of mechanical behavior, electronic structures, and thermodynamic properties can be optimized by mediating the concentration of the titanium alloying element. The results revealed that these transition metal compounds were stable with the negative formation energy. Nb0.5Ti0.5C (29.15 GPa) demonstrated the largest hardness characterized by moduli (B, G) because of the stable shell configuration. NbC exhibited the strongest anisotropy from the universal anisotropic index (AU) and three-dimensional surface contours. TixNb1−xC compounds displayed relatively strong stress responses along the [001], [110], and [111] directions. Due to the weakening p–d bonding, the ideal tensile strength gradually decreased with the increasing titanium concentration. The electronic structures revealed that the bonding characteristics of the (Ti, Nb)C compounds were a mixture of metallic and covalent bonds. On the other hand, NbC and TiC exhibited a minimum (740.55 K) and maximum (919.29 K) Debye temperature, indicating the stronger metalic bonds of NbC and covalent bonds of TiC. [ABSTRACT FROM AUTHOR]

The reliability of Sn-3.0Ag-0.5Cu (SAC 305) solder joint under a broad level of drop impacts was studied. The failure performance of solder joint, failure probability and failure position were analyzed under two shock test conditions, i.e., 1000 g for 1 ms and 300 g for 2 ms. The stress distribution on the solder joint was calculated by ABAQUS. The results revealed that the dominant reason was the tension due to the difference in stiffness between the print circuit board and ball grid array, and the maximum tension of 121.1 MPa and 31.1 MPa, respectively, under both 1000 g or 300 g drop impact, was focused on the corner of the solder joint which was located in the outmost corner of the solder ball row. The failure modes were summarized into the following four modes: initiation and propagation through the (1) intermetallic compound layer, (2) Ni layer, (3) Cu pad, or (4) Sn-matrix. The outmost corner of the solder ball row had a high failure probability under both 1000 g and 300 g drop impact. The number of failures of solder ball under the 300 g drop impact was higher than that under the 1000 g drop impact. The characteristic drop values for failure were 41 and 15,199, respectively, following the statistics. [ABSTRACT FROM AUTHOR]

The microstructure and oxidation kinetics of Fe-B-based alloys at 927 K in air with different boron concentrations of 0.95, 1.45, 2.10, and 3.08 wt% were studied. The alloy microstructures were interpreted to consist of α-Fe, FeB, and pearlite. After 100-h oxidation, the oxides comprised FeO at the surfaces and a mixed BO-SiO layer at matrix/oxide interface. The formation of mixed oxides layer was affected by boron content in the alloy and had obvious influence on the oxide morphology. The isothermal oxidation kinetics at 973 K exhibited initial rapid mass loss followed by slow mass loss, and the oxidation rate constants of the two oxidation stages demonstrated completely opposite tendencies with the increase of boron. The Fe-B 3.08 wt% alloy exhibited the best oxidation resistance after 100 h of cyclic oxidation due to the formation of a well-distributed and continuous BO-SiO mixed oxide layer. [ABSTRACT FROM AUTHOR]

Development of lead-free solders with low melting temperature is important for substitution of Pb-based solders to reduce direct risks to human health and the environment. In the present work, Sn-Bi-In solders were studied for different ratios of Bi and Sn to obtain solders with low melting temperature. The microstructure, thermal properties, wettability, mechanical properties, and reliability of joints with Cu have been investigated. The results show that the microstructures of the Sn-Bi-In solders were composed of β-Sn, Bi, and InBi phases. The intermetallic compound (IMC) layer was mainly composed of CuSn, and its thickness increased slightly as the Bi content was increased. The melting temperature of the solders was around 100°C to 104°C. However, when the Sn content exceeded 50 wt.%, the melting range became larger and the wettability became worse. The tensile strength of the solder alloys and solder joints declined with increasing Bi content. Two fracture modes (IMC layer fracture and solder/IMC mixed fracture) were found in solder joints. The fracture mechanism of solder joints was brittle fracture. In addition, cleavage steps on the fracture surface and coarse grains in the fracture structure were comparatively apparent for higher Bi content, resulting in decreased elongation for both solder alloys and solder joints. [ABSTRACT FROM AUTHOR]

Agglomerated TiB particle and network-like structure-reinforced titanium matrix composite coatings were prepared by laser cladding of the Ni + TiB + Ti preplaced powders on Ti-6Al-4V alloy. The network-like structure mainly consisted of NiTi and NiTi. Through the experiment, it was found that the size of agglomerated particle gradually decreased with the increase of Ti content, but the number of the network-like structure first increased and then disappeared. In-situ reaction competition mechanism and the formation of network-like structure were discussed. The average micro-hardness gradually decreased with the increase of Ti content, but the average fracture toughness gradually increased. Meanwhile, the wear resistance of the coatings is higher than that of the substrate, but the wear loss of the coatings is gradually increased with the increase of Ti content. [ABSTRACT FROM AUTHOR]

The effects of 0.3 wt.% Al added to flowing liquid zinc on the corrosion inhibition and erosion-corrosion interfacial characteristics of Fe-3.5 wt.% B alloy were investigated in order to separate the pure erosion rate from the total erosion-corrosion rate and further study the erosion-corrosion interaction created by flowing zinc. The result indicated that the erosion-corrosion rate increased slowly and then sharply thereafter, while the corrosion-inhibition rate increased linearly and slowly at a bath temperature of 460-550 °C. The corrosion-inhibition efficiency of 0.3 wt.% Al addition in the flowing liquid zinc bath was significantly reduced and then enhanced with increasing bath temperatures, depending on the interfacial microstructures after Al-corrosion inhibition. A uniform and continuous FeAlZn inhibition layer, which suppressed the corrosion reaction of iron and zinc, formed on the erosion-corrosion interface of the Fe-3.5 wt.% B alloy, thereby reducing the spallation of anticaustic FeB skeleton. Moreover, the gradual deterioration of the inhibition layer led to a reduction in the corrosion-inhibition ability. The present results indicate that, due to the beneficial Al-corrosion inhibition effect, the corrosion-inhibition rate as the pure erosion rate of Fe-3.5 wt.% B in flowing liquid zinc can be well separated from the erosion-corrosion rate by adding 0.3 wt.% Al to flowing liquid zinc bath. [ABSTRACT FROM AUTHOR]

The effect of erosion angle on erosion behavior of the as-cast Fe-B alloy in flowing liquid zinc was investigated. The results show that the erosion rate of Fe-B alloy decreases linearly with increasing erosion angle. The erosion resistance of Fe-B alloy is better than that of 316L stainless steel, which is attributed to the favorable barrier effect of net-like FeB that resists erosion by flowing liquid zinc. Meanwhile, the ductile matrix can provide support in preventing borides from spalling and borides cause barrier effect on flowing liquid zinc during liquid zinc erosion, which shows a synergistic erosion-corrosion behavior between the matrix and borides. Moreover, an increase in erosion angle can cause a decrease in the removal effect of the flowing liquid zinc scouring component on the erosion compounds. Therefore, the quantity of erosion compounds increases at the erosion interface, weakening the mass transfer process and decreasing the erosion rate of the Fe-B alloy. [ABSTRACT FROM AUTHOR]

The effect of the element cerium on the microstructure and wear behavior of Fe-B cast alloy was investigated by scanning electron microscope, transmission electron microscope, X-ray diffraction analysis, Leica digital image analysis, hardness tester and abrasion tester. The microstructures of as-cast Fe-B alloy are composed of the phase ferrite, pearlite and eutectic boride. Moreover, the as-cast eutectic boride structures in Fe-B alloy containing cerium are finer than that in the alloy having no cerium. After heat treatment, the average boride area and wear weight loss of the alloy containing cerium are lower than these of the alloy having no cerium. Before the formation of primary austenite, cerium can combine with oxygen to form CeO. CeO can act as nuclei of primary austenite, promoting the refinement of austenite and borides during solidification, and improve the wear property of Fe-B alloy. [ABSTRACT FROM AUTHOR]

The erosion–corrosion properties and interface microstructure of a Fe–B alloy that contains 3.5 wt% B in flowing liquid zinc have been investigated by electron backscattered diffraction, x-ray diffraction, and scanning electron microscopy to clarify the flowing effect of liquid zinc on erosion performance using a rotating-disk technique. The Fe–B alloy erodes at a low and steady rate in flowing liquid zinc. Flowing liquid zinc can accelerate the iron and zinc mass transfer to form Fe–Zn compounds and promote the removal of loose FeZn13. Much residual corrosion-resistant Fe2B and some erosion products coexist at the erosion interface because of the chemical and micromechanical effects that are created by flowing liquid zinc. The failure of the Fe2B corrosion-resistant skeleton in flowing liquid zinc occurs because of the loss of supporting matrix and also the formation and spread of microcracks during erosion. [ABSTRACT FROM PUBLISHER]

This study investigates the effect of cerium on the microstructures, mechanical properties of medium carbon Fe-B cast alloy. The as-cast microstructure of Fe-B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the unmodified alloy, the eutectic boride structures in the modified alloy are greatly refined. Cerium promotes the formation of CeO phase. CeO can act as effective heterogeneous nuclei of primary austenite, and refine austenite and boride. After heat treatment, the impact toughness of the modified alloy is higher than that of the unmodified alloy because there are more broken borides in the modified alloy. Meanwhile, the fracture mechanism of medium carbon Fe-B alloy is depicted and analyzed by using fractography. [ABSTRACT FROM AUTHOR]

The effects of Fe2B-grain orientation on microstructure and properties of bulk Fe2B intermetallic fabricated by directional and ordinary solidification techniques have been investigated. The results show that unidirectional solidified Fe2B intermetallic possesses a strong (002) texture in the transverse direction owing to the opposite unidirectional heat-squeeze effect while random Fe2B grains can be produced under ordinary solidification conditions. The nonoriented Fe2B intermetallic has the highest linear expansion coefficient of 13.04 × 10−6 °C−1 while the microhardness and fracture toughness of transverse Fe2B intermetallic in the (002) plane are larger than those of Fe2B with other grain orientations and their values are ∼18.72 GPa and 6.42 MPa·m1/2, respectively. Liquid zinc corrosion results indicate that unidirectional Fe2B intermetallic with long axis perpendicular to the direction of liquid zinc corrosion displays the best corrosion resistance to liquid zinc owing to its beneficial barrier effect. The FeB transition phase can naturally form and grow parabolically during liquid zinc corrosion. [ABSTRACT FROM PUBLISHER]

In the present study, the microstructure and mechanical properties of cast Fe-10Cr-1.5B (FCB) alloy after different heat treatments were studied. The results showed that the as-cast microstructure of FCB alloy consists of a-Fe, M(M=Cr, Fe, Mn)2(B, C) and M(M=Cr, Fe, Mn)7(C, B)3 type borocarbides, and small amounts of pearlite and austenite. After oil quenching treatment, metal matrix transformed into the martensite from the mixture of martensite, pearlite and austenite. There are many M(M=Cr,Fe,Mn)23(C,B)6 type borocarbide precipitates in the metal matrix, and eutectic borocarbide appears with an apparent disconnection and isolated phenomenon. When the quenching temperature reaches 1,050 °C, the hardness of FCB alloy is the highest, but the change of quenching temperature has no obvious effect on impact toughness of FCB alloy. After tempering, the eutectic microstructure of FCB alloy appears with a "two links" trend. With the increase of tempering temperature, the hardness of FCB alloy decreases gradually and impact toughness increases gradually. Cast FCB alloy oil-quenched from 1,050 °C and tempered from 200 °C has excellent combined properties; its hardness and impact toughness are 61.5 HRC and 8.8 J•cm-2 respectively. [ABSTRACT FROM AUTHOR]

This study investigates the effect of titanium and nitrogen elements on the microstructures and wear behaviors of medium carbon Fe-B cast alloy. The as-cast microstructures of Fe-B cast alloy consist of the eutectic boride, pearlite, and ferrite. Moreover, the as-cast eutectic boride structures are greatly refined when titanium and nitrogen are added. The boride area fraction, average boride area, Rockwell hardness, etc., are also investigated systemically. The wear behaviors of medium carbon Fe-B cast alloy are studied by a three-body abrasive wear tester. The results show that the wear weight loss of Fe-B cast alloy with titanium and nitrogen elements is lower than that of the ordinary Fe-B cast alloy. Meanwhile, the wear mechanism of Fe-B cast alloy with different titanium and nitrogen concentrations is described and analyzed. [ABSTRACT FROM AUTHOR]

The effects of titanium and nitrogen elements on the microstructure and impact toughness of the Fe-B alloy have been studied. The results show that the borides are refined after the additions of titanium and nitrogen elements. With the additions of titanium and nitrogen, titanium nitrides are formed in the Fe-B alloy. Titanium nitride can act as effective heterogeneous nuclei of primary austenite, and promote the refinement of austenite and boride. After heat treatment, the impact toughness of Fe-B alloys modified by titanium and nitrogen elements is higher than that of ordinary alloy. [ABSTRACT FROM AUTHOR]

Microstructure, mechanical properties, and wear resistance of B-bearing high-speed steel (HSS) roll material containing 0.90-1.00% C, 1.3-1.5% B, 0.8-1.5% W, 0.8-1.5% Mo, 4.6-5.0% Cr, 1.0-1.2% V, and 0.15-0.20% Ti were studied by means of the optical microscopy (OM), the scanning electron microscopy (SEM), x-ray diffraction (XRD), hardness, impact toughness, and pin-on-disk abrasion tests. The results showed that as-cast structure of B-bearing HSS consisted of α-Fe-, M(B,C)-, M(BC)-, and M(B,C)-type borocarbides, a small quantity of retained austenite, and a small amount of TiC. The hardness and impact toughness values of as-cast B-bearing HSS reached 65-67 HRC and 80-85 kJ/cm, respectively. There were many M(B,C)-precipitated phases in the matrix after tempering, and then, with increasing temperature, the amount of precipitated phases increased considerably. Hardness of B-bearing HSS gradually decreased with the increasing tempering temperature, and the change of tempering temperature had no obvious effect on impact toughness. B-bearing HSS tempered at 500 °C has excellent wear resistance, which can be attributed to the effect of boron. [ABSTRACT FROM AUTHOR]

Influences of the tempering temperature on the microstructure, mechanical property and wear resistance of High-Boron High Speed Steel (HBHSS) roll materials were investigated by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, hardness measurement, impact tester, tensile tester and pin abrasion tester. The results show that the as-cast structure of HBHSS consists of a great amount of martensite and M2(B,C) and a few retained austenites and M23(B,C)6. After solution treated at 1,050 °C and followed by oil cooling, the amount of M23(B,C)6 carbo-borides in quenched HBHSS increases obviously and the macrohardness of the quenched HBHSS is 66 HRC, which is very close to the 65.8 HRC of as-cast HBHSS. On the whole, the hardness of HBHSS alloy shows a trend of slight decrease with increasing tempering temperature when tempered below 500 °C. While when above 500 °C, the hardness increases slightly as the tempering temperature increases and reaches a peak at 525 °C and then decreases obviously. The impact toughness of HBHSS has a tendency to increase as the tempering temperature increases. Tempering can improve the tensile strength and elongation of HBHSS, but a higher tempering temperature causes a slight decrease in both tensile strength and elongation. Excellent wear resistance can be obtained by tempering at 500 to 550 °C. [ABSTRACT FROM AUTHOR]

The microstructures of Fe-B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe-B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe-B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe-B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe-B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron. [ABSTRACT FROM AUTHOR]

We prepared Al/Cu/steel composite with a gradient structure using a vacuum hot-pressed diffusion method and investigated the Al/Cu/steel interface. The results show that a supersaturated solid solution with a thickness of about 2 um formed in the Cu/steel diffusion zone. Two kinds of intermetallic compounds, CuAl adjacent to the Cu side and CuAl adjacent to the Al side, formed at the interface of the Al/Cu. The thickness of the intermetallic compound layer appeared to greatly affect conductivity and tensile strength. The conductivity and the tensile strength decreased from 36.9 MS/m to 24.2 MS/m, and from 70.9MPa to 40.7MPa, respectively, while the thickness increased from 3.5 um to 23 um. The fractures occurred between a supersaturated solid solution (Al in Cu) and CuAl, or between CuAl and CuAl. [ABSTRACT FROM AUTHOR]

The effects of quenching treatment on the microstructure, hardness, impact toughness, and wear resistance of low-carbon high-boron cast steel (LCHBS) containing 0.15–0.3 %C, 1.4–1.8 %B, 0.3–0.8 %Si, 0.8–1.2 %Mn, 0.5–0.8%Cr, 0.3–0.6%Ni, and 0.3–0.6%Mo have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and via an electron probe microanalyzer (EPMA), X-ray diffraction (XRD) analysis, impact tester, hardness tester, and wear tester. The as-cast matrix of LCHBS consists of pearlite and ferrite. There is 8–10 vol.% Fe2(B, C) type borocarbides in the matrix. The micro-hardness of Fe2(B, C) is 1430–1480 Hv. Fe2(B, C) shows no obvious change and the matrix completely transforms into lath martensite upon quenching at 900 °C to 1100 °C. The microhardness of the matrix and the macrohardness of the LCHBS sample show a slight increase with an increase of homogenization temperature. When the homogenization temperature exceeds 1050 °C, no distinct change in the hardness is observed. The change of homogenization temperature has no apparent effect on the impact toughness of LCHBS. The mass losses of LCHBS increase distinctly when the wear load increases. The homogenization temperature is less than 1000 °C and the wear rate of LCHBS decreases with an increase of temperature. The wear rate does not display any obvious change after exceeding a homogenization temperature of 1000 °C. [ABSTRACT FROM AUTHOR]