•Friction stir processing was fabricated AA2024/SiC by different passes number.•The effect of post heat treated on wear behaviour were analyzed.•By increasing number of passes, hardness of SZ ...decreased by increasing of S-phases.•Post heat treated increased the hardness due to dissolving the bigger S-phase.•The wear mechanism was the adhesive one in the composite and base metal samples.
Aluminium matrix nano-composites were produced by friction stir processing of an Al-Cu alloy at different number of passes with pre-inserted SiC particles. The metal matrix composites were supplementary heat treated to elucidate the effect of heat treatment on microstructural changes and mechanical properties. The samples were fabricated by two and four passes. The supplementary heat treatment consisted of annealing at 590°C for 1h and artificial aging at 180°C for 8h. Microstructural studies showed that fine and co-axial grains along with uniform distribution nano-particles were formed in the stir zone (SZ). The agglomerated nano-scale particles were also observed in the samples. Micro-hardness results presented that in the SZ-region, hardness decreased with increasing the number of passes in the samples that were not heat treated. However, hardness uniformly increased about 70HV in the heat-treated samples. Wear mechanism in all of the samples was adhesive mechanism and the value of wear resistance increased about 170% in the heat-treated samples. The obtained results showed that the improvement of hardness and wear resistance in the heat-treated sample was related to the change in size and distribution of the S-phase precipitates in microstructure.
In this study, a dissimilar joint of cobalt based superalloys X-45 and FSX-414 has been created under the standard heat treatment conditions with the nickel-based BNi-9 interlayer with the thickness ...of 50 μm by the transient liquid phase bonding process. Solution heat treatment (1150 °C/4 h) was used for bonding and the aging heat treatment (980 °C/4 h) for the homogenization of the bond. Optical metallography, Field Emission Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy, Differential scanning calorimetry, micro-hardness test and shear strength test were used for the characterization of microstructural and mechanical evolution in base metals and bonds. The solution heat treatment leads to the dissolution of a part of the M
23
C
6
and M
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C carbides in the substrate of superalloys, which due to the aging heat treatment secondary and fine carbides M
23
C
6
precipitate in the substrate and help strengthen the superalloys. The diffusion of the boron from the molten interlayer to the base metals resulted in the complete isothermal solidification and a nickel-based single-phase solid solution has been developed. Cobalt-chromium-tungsten-molybdenum-based carboborides precipitation with high hardness in the vicinity of the isothermal solidification zone and in base metals results in the non-homogeneity of microhardness profile along the bonding area. Homogenization heat treatment did not have an effect on the omission of these precipitations, but by more uniform redistribution of the alloying elements strengthen solid solution that could increase shear strength from 655 to 688 MPa, which is somewhat equivalent to the shear strength of the 45-X alloy and also 93% of the shear strength of the FSX-414 alloy.
Graphic Abstract
Abstract
In this study, the effect of alteration in the direction of forming during the shear spinning of C11000 copper metal on mechanical properties, microstructure, texture, and anisotropy was ...investigated. Shear spinning causes the grains stretching along the axial direction besides increasing the grain length in the circumferential direction. Strain-path change in the shear spinning specimens has somewhat resulted in finer grains, more grain refinement, and a higher percentage of high-angle boundaries. More change of strain direction in the shear spinning specimens resulted in approximately 9% to 11% reduction in strength, from 1% to 9% decrease in hardness, and increased elongation from 7% to 37% more than in the specimen without path change. Shear spinning specimens in different paths had different orientations and texture intensities. In the specimen without strain-path change, most of the texture is related to {123}〈412〉 orientation and copper texture with {112}〈111〉 orientation. In the shear spinning specimens in other paths, textures with {001}〈100〉, {011}〈011〉, and {211}〈011〉 orientations and brass texture with {110}〈112〉 orientation were strengthened. Due to the change in texture and mechanical properties, the strain-path change in the shear spinning process reduced the anisotropy in the C11000 copper metal.
Phase transformations and the melting range of the interlayer BNi-3 were investigated by differential scanning calorimetry, which showed three stages of crystallization during heating. There were ...three exothermic peaks that indicated crystallization in the solid state. The cobalt-based X-45 and FSX-414 superalloys were bonded with interlayer BNi-3 at a constant holding time of 10 min with bonding temperatures of 1010, 1050, 1100, and 1150 °C using a vacuum diffusion brazing process. Examination of microstructural changes in the base metals with light microscopy and scanning electron microscopy coupled with X-ray spectroscopy based on the energy distribution showed that increasing temperature caused a solidification mode, such that the bonding centerline at 1010 °C/10 min included a γ-solid solution, Ni3B, Ni6Si2B, and Ni3Si. The athermally solidified zone of the transient liquid phase (TLP)-bonded sample at 1050 °C/10 min involved a γ-solid solution, Ni3B, CrB, Ni6Si2B, and Ni3Si. Finally, isothermal solidification was completed within 10 min at 1150 °C. The diffusion-affected zones on both sides had three distinct zones: a coarse block precipitation zone, a fine and needle-like mixed-precipitation zone, and a needle-like precipitation zone. By increasing the bonding temperature, the diffusion-affected zone became wider and led to dissolution.
Cobalt-based X-45 and FSX-414 superalloys with interlayer BNi-9 have been bonded by a transient liquid phase bonding process at a constant temperature of 1150 °C with the holding times of 1, 10, 60, ...120, 180 and 240 min. Microstructural changes of base metals showed that the conditions of 1150 °C/240 min can be used to joint base metals, in such a way that the primary carbides of M6C and M23C6 are significantly dissolved in the matrix, forming a supersaturated solid solution. Examination of the bonded specimens showed that during heating up to the bonding stage, Nickel-rich carbo-boride deposits are formed at the interface between the filler metal and the base alloys due to the solid-state diffusion of boron element. The next generation of carbo-borides is formed in the diffusion affected zone of the base metals, which are also Cobalt–Chromium–Tungsten–Molybdenum-rich carbo-borides. Bonding at 1150 °C/1 min resulted in lack of complete diffusion of boron element into the base metals; quasi-eutectic compounds γ, Ni3B and CrB were formed in the centerline of the bond and, increasing the holding time causes the interdiffusion of alloying elements of base metals and the interlayer and leads to the uniformity of the chemical composition along the joint. Bonding under standard solution heat treatment condition (1150 °C/240 min) completely removes the diffusion affected zone on the 45-X side.
The dissimilar joining of martensitic and ferritic stainless steels have been developed that needs corrosion resistance and enhanced mechanical properties. In this study, the transient liquid-phase ...bonding of martensitic stainless steel 410 and super-ferritic stainless steel 446 was conducted with a nickel-based amorphous interlayer (BNi-2) at constant temperature (1050 °C) and increasing times of 1, 15, 30, 45, and 60 min. For characterization of the TLP-bonded samples, optical microscopy and scanning emission microscopy equipped with energy-dispersive X-ray spectroscopy were used. To investigate the mechanical properties of TLP-bonded samples, the shear strength test method was used. Finally, the X-ray diffraction method was used for microstructural investigation and phase identification. The microstructural study showed that the microstructure of base metals changed: the martensitic structure transited to tempered martensite, including ferrite + cementite colonies, and the delta phase in super-ferritic stainless steel dissolved in the matrix. During the transient liquid-phase bonding, the aggregation of boron due to its diffusion to base metals resulted in the precipitation of a secondary phase, including iron–chromium-rich borides with blocky and needle-like morphologies at the interface of the molten interlayer and base metals. On the other hand, the segregation of boron in the bonding zone resulted from a low solubility limit, and the distribution coefficient has induced some destructive and brittle phases, such as nickel-rich (Ni3B) and chromium-rich boride (CrB/Cr2B). By increasing the time, significant amounts of boron have been diffused to a base metal, and diffusion-induced isothermal solidification has happened, such that the isothermal solidification of the assembly has been completed under the 1050 °C/60 min condition. The distribution of the hardness profile is relatively uniform at the bonding zone after completing isothermal solidification, except the diffusion-affected zone, which has a higher hardness. The shear strength test showed that increasing the holding time was effective in achieving the strength near the base metals such that the maximum shear strength of about 472 MPa was achieved.
The effect of bonding temperature and bonding time on the microstructure of transient liquid phase (TLP) bonding named GTD111 and IN718 superalloys, using a commercial Ni–B–Cr filler alloy (BNi-2) ...interlayer were evaluated. The sandwich assembly was kept in a vacuum furnace at temperatures of 1050, 1100, and 1150 °C for 1, 15, 30, 45, 60, and 80 min until the TLP process occurred. Microstructural characterization was carried out via optical microscopy, scanning electron microscopy (SEM) equipped with field emission energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Microstructural assessments displayed those in little bonding times, the joint microstructure includes continuous eutectic intermetallic phases and longer times cause eutectic free microstructure. The bonding temperature affects the isothermal solidification rate, while, at low bonding temperatures microstructure of the joint centerline is controlled by diffusion of melting point depressant (MPD) elements. Despite, at high bonding temperature effect of base metal alloying elements on the joint microstructure development was more marked. The results showed that athermally solidified zone (ASZ) size reduces with increasing bonding temperature and time due to diffusion of boron into the base metal.
Dissimilar transient liquid phase (TLP) bonding of GTD-111 and IN-718 nickel-based superalloys was investigated using BNi-9 (AWS A5.8/A5.8M) as an interlayer. The effect of the bonding time on the ...microstructure and mechanical properties of the TLP-bonded specimens was studied at 1100 °C using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS), and micro-hardness and shear strength analyses. Joint microstructural studies revealed that at the bonding times shorter than 75 min, nickel- and chromium-rich borides were formed with the joint centerline. The volume fraction of intermetallic compounds decreased with the increase of the bonding time and the diffusion of boron element whereby the isothermal solidification eventually completed after 75 min. Micro-hardness investigations along the bonding joint showed that the hardness of an isothermal solidification zone (ISZ) decreased with the completion of isothermal solidification. The hardest zone in the joint structure belonged to the athermal solidification zone (ASZ). The shear strength test results showed that incrementing the bonding time increased the shear strength where the shear strength value at 1 min/1100 °C (320 MPa) raised to 590 MPa after the completion of isothermal solidification.
Carbide-free bainitic (CFB) steels with a matrix of bainitic ferrite and thin layers of retained austenite, to reduce the manufacturing costs, usually do not contain alloying elements. However, a few ...reports were presented regarding the effect of alloying elements on the properties of these steels. Thus, this study evaluates the effects of vanadium and rare earth (Ce-La) microalloying elements on the structure, phase transformation kinetics, and mechanical properties of carbide-free bainite steel containing silicon fabricated by the casting and austempering procedure. Optical and scanning electron microscopy (OM and SEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) were used to study the microstructure and phase structure. The transformation kinetics were examined by a dilatometry test. Hardness, tensile, and impact tests evaluated the mechanical properties. Due to adding alloying elements, the fracture toughness and change in matrix phases relation was studied by the crack tip opening displacement (CTOD) test and SEM fractography. The microstructure of the silicon added sample was completely carbide-free bainite. The test results showed vanadium helped CFB formation, even in continuous cooling. The primary austenite grain (PAG) size grew by vanadium addition. The EBSD phase map illustrates an increment in the percentage of retained austenite by vanadium. In contrast, the addition of 0.03 wt% rare earth reduced the primary austenite grain size and reduced the retained austenite content. The results of the dilatometry test confirmed that vanadium and rare earth addition both reduced the critical cooling rate of the bainite transformation. Vanadium leads to an earlier cessation of bainite transformation, while rare earth elements postpone this transformation. Mechanical tests showed that the tensile strength of carbide-free bainite steels was strongly influenced by the morphology and volume fraction of austenite. Retained austenite, when transformed to martensite during the transformation-induced plasticity (TRIP) phenomenon, leads to increased tensile strength and fracture toughness, or retained austenite with a film-like shape prevents the growth of cracks by blinding the crack tip. The result of the CTOD test exhibited that retained austenite plays the leading role in increasing crack resistance when TRIP occurs.
A sort of biodegradable magnesium-based nanocomposites improved by nano-sized NiTi particles has been offered in the current research with the evaluations for implant application. The samples were ...provided through mechanical alloying followed by sintering; the assessments consisted of microstructure, mechanical properties, and in-vitro biocompatibility. The impacts of integrating 15, 30, and 45 wt% of NiTi nano-particles on the characteristics of Mg–3Zn-0.5Ag magnesium alloy matrix have been investigated. The addition of 15 wt% of NiTi led to a decline in the grain size by 10.5%, an increase in the compressive strength by 56%, and a rise in the elongation by 7.6% as compared to the matrix; whereas further reinforcement addition reduced the elongation and compressive strength. The addition of 15 wt% NiTi causes a minor increase in corrosion rate, but incorporating 30 and 45 wt% of NiTi content result a major increase in corrosion rate. The improved compressive mechanical properties may be ascribed to Hall-Petch impact, the load transfer from matrix to NiTi particles, Orowan strengthening mechanism, and locking of dislocations owing to the occurrence of hard NiTi reinforcement particles. In-vitro biocompatibility tests such as MTT and DAPI assay revealed that the nanocomposites are appropriate for medical uses. It may be stated that the nanocomposite comprising 15 wt% of NiTi can be used appropriately as an orthopedic implant biomaterial.
•Mg-based nanocomposites containing NiTi nanoparticles were prepared via mechanical alloying followed by sintering.•Addition of NiTi nanoparticles significantly increased mechanical properties of Mg-based composites.•Strengthening mechanisms of the Mg-based nanocomposites containing NiTi nanoparticles is proposed.•Mg-based nanocomposites containing NiTi nanoparticles presented good biocompatibility.
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