Solution and aging heat treatment (SAT) is an effective method for enhancing the mechanical properties of maraging steel. The solution temperature is a key factor affecting the SAT; however, there is a lack of research on the effect of solution temperature on the organizational properties of wire arc additive manufacturing (WAAM) maraging steel. In this study, thin-walled structures of maraging steel were prepared using WAAM. The microstructures and mechanical properties of the As-deposited (AD) and SAT specimens subjected to varying solution temperatures were systematically analyzed and compared. The AD specimen exhibited obvious segregation behavior of Ti, Mo, and other alloying elements and an anisotropic microstructure and mechanical properties. Following the SAT, the strength of the maraging steel significantly increases due to the generation of nanoprecipitated phase. The ultimate tensile strength (UTS) of the AD specimen is 1282.5 MPa, and that of the 900 degrees C SAT specimen is 1530.8 MPa. At higher solution temperatures, the element distribution is more homogeneous, and the nano-precipitated phases are finer, resulting in a higher strength. The UTS of the 1000 degrees C SAT specimen increases to 1732.7 MPa. However, at a solution temperature of 1100 degrees C, the UTS decreases to 1634.1 MPa because of the increase in the grain size and prior austenite grain size. It has been shown that a reasonable solution temperature can attenuate elemental segregation precipitation and promote the generation of a nanoprecipitation phase to enhance the performance of the maraging steel without excessively coarsening the grain.

Reduced activation ferritic/martensitic (RAFM) steel with high strength and neutron radiation damage resistance is deemed one of the promising structural materials for fusion blankets. In this study, RAFM steel tube was prepared through wire arc additive manufacturing, and the evolution of phase composition, microstructural features and mechanical properties during the as-built and heat treatment processes were investigated. The results show that the as-built state is predominantly composed of alpha-Fe, and the microstructure's morphology from bottom to top consists of alternating columnar grain regions, equiaxed coarse grain regions, and fine grain regions. Normalizing and tempering treatment eliminates the heterogeneous microstructure, resulting in the presence of M23C6 carbides enriched with Cr and W, as well as MX phases enriched with Ta and V. Partitioning heat treatment results in the formation of ultrafine martensitic, quenched martensite and bainitic microstructures. The mechanical properties of wire arc additively manufactured RAFM steel are influenced by variations in microstructure. The coarse-grained region formed in the as-built state represent weak links. Normalizing and tempering treatment reduces the strength while improving ductility. Partitioning heat-treated RAFM steel exhibited a high strength of 1.1 GPa and an elongation of approximately 10.9%. This study provides a method of combining additive manufacturing with heat treatment to enhance the strength and ductility of RAFM steel simultaneously.

To investigate the thermal effect of the titanium (Ti) adhesion layer on the evolution of structure and properties of platinum (Pt) films, Pt films with different thicknesses of Ti adhesion layers were prepared using magnetron sputtering followed by vacuum heating. Results show that Ti particles diffused into the Pt film, and the level of Ti content on the surface is positively correlated with the proportion of Ti layer thickness. After high temperature annealing, particle agglomeration and recrystallization of pure Pt films are intensified. Introduction of Ti adhesion layer can inhibit dewetting. With the increase of heat temperature, the enhanced atomic mobility leads to the intensification of Ti diffusion, and the alloying with Pt occurs more fully. The dominant phase in the film gradually changes from Pt to Pt8Ti and then Pt3Ti phase. Although the formation of intermetallic compounds leads to a gradual increase of the electrical resistivity, the introduction of Ti layer can greatly improve the adhesion force of the film and the substrate. In addition, due to that the Pt layer on the Ti layer can relieve some of the tensile stresses through deformation, the addition of the Ti layer can decrease the residual stress of the film.

X80 high-grade pipeline steel is the main material used in long-distance oil and gas transmission pipelines. During the application process, it was found that there was a significant difference in the toughness of the weld metal after welding steel plates from different manufacturers, which seriously affected the safety of oil and gas storage and transportation. There was an urgent need for a fast and accurate in-situ quantitative analysis method for the distribution of elements along the thickness direction of the weld seam to help explore the mechanism of the joint effect of X80 pipeline steel base material and welding material on the toughness of the weld metal. Therefore, this article proposed a method for in-situ quantitative analysis of Mn, Ni, Cr, Al, and Nb in weld using LA-ICP-MS. By optimizing the laser pulse frequency to 20Hz, laser energy to 100% (laser output mode Image Aperture), etching aperture to 100 mu m, and defocus distance 0 mu m, the strength and the stability of mass spectrometry signals were enhanced. The experiment was calibrated using standard samples matched with the matrix, and the matrix element Fe-57 was used as the internal standard for correction. By analyzing related mass spectrometry interferences, isotopes Al-27, Cr-53, Mn-55, Ni-60, and Nb-93 were selected. The established LA-ICP-MS micro zone in-situ quantitative analysis method was applied to analyze the distribution of element content in two X80 pipeline steel welds with the same welding material but different base material compositions. The correlation coefficient of this method ranged from 0.992 7 to 0.999 6, with a quantification limit of 0.23 similar to 2.57 mu g.g(-1). The results showed that Mn, Cr, Al, and Nb with similar contents in the two base metals exhibited similar dilution at the root of the weld. In comparison, Ni elements with significant differences in content between the two base metals showed significant differences in content within 8.4 mm from the root of the weld. The impact test results showed that the toughness of weld with high Ni element content in the base material is relatively significantly higher. SEM analysis of weld root showed that the increase of Ni element content was conducive to forming lath bainite structure. Therefore, it is considered that the dilution of base metal to Ni in the root weld metal can be reduced by adding 0.14% Ni to X80 pipeline steel. The weld impact toughness can be improved by higher Ni content by promoting the low-temperature lath bainite transformation. The established LA-ICP-MS in-situ quantitative analysis method is of reference significance for ensuring the safe operation of the X80 long-distance pipeline.

At present, in the process of weld induction heat treatment, the common method is to carry out centralized induction heating in the weld area, which will lead to large radial temperature difference of the weld, poor controllability of temperature distribution and easy to cause the defects of residual stress concentration in the weld area. To solve the above problems, this paper adopts the two-sided method to conduct induction heating on both sides of the weld, and at the same time, the auxiliary pulse current is passed into the weld to improve the quality of the weld. ANSYS finite element software is used to establish a multi-field coupling prediction model of electric-magnetic-thermal structure, and explore the distribution law of the auxiliary pulse current and the temperature field of the weld. Finally, an experimental study of pulsed current assisted two-sided induction heating is carried out. Temperature test and metallographic test were carried out respectively to verify the effectiveness of pulsed current assisted induction heating technology.

Nb-lean Cu–Cr–Nb alloys have been widely applied in electrical industries as the structural conductive material owing to their excellent combination of the mechanical and electrical properties at room temperature. In this work, the influence of temperature during fast sintering and post-heat treatment strategies on the precipitate evolution and room temperature mechanical properties of the Cu–3Cr-0.5Nb (wt.%) alloy was investigated. The increasing sintering temperature will improve the density and mechanical properties of the alloy without any obvious grain growth during this non-equilibrium process, while the post-aging at lower and higher temperatures can effectively control the formation and coarsening process of the Cr-based precipitates. Systematic characterization was then conducted on the microstructural evolution, especially the altering precipitates’ size and distribution, in the alloy at both as-sintered and the aged conditions, which is correlated to its room temperature tensile properties. Lower aging temperature will induce the nucleation of the new Cr2Nb precipitates without causing a significant coarsening of the existing precipitates like aging at higher temperature. Therefore, the low-temp. aged sample exhibits the highest tensile strength and elongation due to the enhanced Orowan strengthening mechanism induced by its unique precipitate microstructure.

In this work, the microstructural evolution and mechanical properties of 0.01 wt% boron microalloying low carbon reduced activation ferritic/martensitic (RAFM) steel with various nitrogen content were studied. The results show that nitrogen could greatly reduce the dimension and volume fraction (f(V)) of M23C6 carbides and increase the f(V) of MX carbonitrides. Fine BN inclusions with the dimension of similar to 200 nm could form with the addition of 0.01 wt% nitrogen, while clustered BN inclusions with the dimension of similar to 6 mu m could be found by 0.02 wt% nitrogen added. The higher nitrogen could result in the higher f(V) and number density of MX carbonitrides, which contribute to the higher dislocation density and dislocation strengthening. However, the strength and toughness of RAFM steel deteriorated by clustered BN inclusions.

The microstructure and mechanical properties of microalloyed low-carbon reduced activation ferritic/ martensitic (RAFM) steel after austenitization at 950 degrees C, 1000 degrees C and 1050 degrees C for 0.5 h and tempering at 750 degrees C for 1.5 h were investigated using scanning electron microscopy, transmission electron microscopy, electron back scattering diffraction, X-ray diffraction, tensile tests, and impact tests. The grain size and lath width obviously increase because more M23C6 carbides dissolve after austenitization at 1050 degrees C. Besides, more fine MX particles would precipitate and result in higher dislocation density. Furthermore, the strengthening mechanisms at room temperature were also systematically discussed, the predominant strengthening mechanism changes from grain boundary strengthening and dislocation strengthening to dislocation strengthening when the austenitizing temperature increases from 950 degrees C to 1000 degrees C and 1050 degrees C. After taking the microstructure, strength, ductility, and toughness into thorough consideration, the optimum austenitizing temperature for microalloyed low-carbon RAFM steel is about 1000 degrees C.

A novel method for reducing the amount of M 23 C 6 carbides, increasing the amount of MX carbonitrides, and decreasing the coarsening rate of M 23 C 6 carbides is put forward to improve the high-temperature properties of reduced activation ferritic/martensitic (RAFM) steel. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, tensile tests, and impact tests are used to systematically investigate the microstructure evolution and mechanical properties of RAFM (RAFM-0.1C) steel, low-carbon RAFM (RAFM-0.04C) steel, and minor boron and nitrogen microalloyed low-carbon RAFM (RAFM-CBN) steel. Some δ ferrite develops when C decreases from 0.1 to 0.04 wt% and subsequently disappears after 0.01 wt% N addition. The amount and size of M 23 C 6 carbides and dislocation density decrease with the decrease of C (RAFM-0.04C), while the amount of MX carbonitrides is 2-3 times, and dislocation density is ≈2 times higher than that of RAFM-0.04C steel after 0.01 wt% N addition (RAFM-CBN). Compared with RAFM-0.1C steel, the yield strength at room temperature and 550 °C slightly decreases for RAFM-0.04C steel and considerably increases for RAFM-CBN steel. The contributions of microalloy on strengthening mechanisms of RAFM steel at room temperature are also systematically revealed by combining the experimental and theoretical data.

Solid diffusion bonding of China low activation martensitic (CLAM) steels was performed. The bonding process was designed based on the austenite transformation, and the austenite transformation information was obtained by using high-resolution dilatometer prior to diffusion bonding. The reliable joining between CLAM/CLAM steels was obtained by using a two-step diffusion bonding procedure. Ultrasonic non-destructive testing revealed no lack-of-bonding porosities at the diffusion bonding interface. Details on interfacial microstructure and mechanical properties of diffusion bonded joint were investigated. Microstructure analysis showed the uniform distribution of elements across the joint, and there was no significant microstructure gradient at the vicinity of the joint. The tensile properties of diffusion bonded samples are almost identical to those of base metal. However, the fracture position of the diffusion bonded samples was located on the base materials, which is related to the finer martensite near the joint zone.

Effects of CeO 2 on the crack resistance and corrosion resistance of TiC/Co-based composite coatings are studied. The microstructure, morphology and element distribution, as well as the phase composition of the coatings were analyzed by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The results demonstrate that adding a small amount of CeO 2 can make the microstructure of the coating more uniform and effectively improve the crack resistance and corrosion resistance of the coating. The addition of CeO 2 can promote the dissolution of TiC particles in the original powder during laser cladding, and then re-nucleate with CeO 2 as the nucleation sites, producing new refined TiC particles. In addition, the potentiodynamic polarization curves confirmed that with the increase in CeO 2 content, the corrosion potential of the coating increased and the corrosion current decreased, indicating that the corrosion resistance of coating was increased.

The sulfuration corrosion behavior of Inconel 600 alloy in high-temperature flue gas was investigated. The element distribution around corrosion layer, corrosion morphology and the phase composition of the corrosion layer were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. The results indicate that the alloy is susceptible to be corroded in high-temperature sulfur-containing atmosphere. The corrosion mechanism is that, on the one hand, sulfur (S) could penetrate the Cr2O3 oxide layer, diffuse into the matrix along the grain boundary, combine with chromium (Cr) to form Cr sulfide and weaken the intergranular bonding strength. On the other hand, sulfur (S) in the flue gas and nickel (Ni) in the alloy matrix form Ni3S2 with low melting point, which is continuously generated and melted during service, and eventually results in the constant occurrence of sulfuration corrosion.

Abstract In this paper, similar and dissimilar 2A12 and 6061 aluminum alloy sheets are joined validly by self-piercing riveting, and a quasi-static experiment is performed to investigate the mechanical behaviors, failure modes and mechanisms of the joints. Also, a method based on deep learning algorithm to detect the appearance defects of the joints is proposed. The results show that the joints with similar 2A12 sheets contained the best static strength, the joints with similar 6061 sheets had superior anti-vibration performance, the joints with 6061-2A12 sheets presented the most decent comprehensive mechanical properties. The main failure mode of joints with similar 2A12 sheets was substrate fractured; the main failure mode of the other joints was pulled-out, and some of them with button-off. The fracture of 2A12 substrate belongs to the composite intergranular and microporous aggregate fracture. The method effectiveness was verified by experiments, and method detection accuracy could reach about 90%, and the detection speed was as high as 50FPS, which can effectively solve the problem that riveting quality was difficult to monitor.

Effects of bonding pressure on solid diffusion bonding of reduced activation ferritic/martensitic (RAFM) steel were investigated at a bonding temperature of 1050 degrees C for 60 min. Microstructure examination indicated that Cr-rich continuous oxides were formed at the bonding interface when the applied pressure was 10 MPa, deteriorating bonding quality of diffusion bonded joint. As the bonding pressure was increased to 20 MPa, uniform and consistent grains were formed at the bonding interface, exhibiting better diffusion bonding effect. The joints obtained under 10 MPa were characteristics of brittle fractures, and the fracture originated from the bonding interface. However, the joints obtained under 20 MPa failed at the base steel, and the fractures were characteristics of ductile fractures with dimples. Finite element analysis indicated that the increase in pressure could lead to the increase in strain at the bonding interface, which can effectively damage the continuous chromium oxide at the bonding interface, improving the bonding strength of the joints.

Reduced activation ferritic/martensitic (RAFM) steel is an iron-based alloy as a candidate structural material in fusion reactor. This paper evaluates the compatibility of RAFM steel as a choice material for wire arc additive manufacturing (WAAM). Two specimens of RAFM steels with high and low heat input were fabricated by WAAM. The effects of the heat input on the microstructure, microhardness and tensile properties of samples were investigated. The fusion boundaries are spaced uniformly in the whole sample. Three distinctive zones were present in the periodic region, including heat-affected zone (HAZ), columnar grains zone and fine-grained zone occurred alternatively. The HAZ was affected by the heat input. The fully γ-annealed top region consisted of epitaxial elongated grains without HAZ. The periodic pattern in microhardness along the building direction was found which was related to the periodic microstructure featured. The tensile properties presented anisotropic characteristics due to the heterogeneous microstructure. Further analysis indicated that the grain coarsening in the HAZ and C precipitates distributed at the grain boundaries caused substantial softened in the HAZ, resulted in the lower localized microhardness and tensile strength. Compared to the high heat input specimen, the low heat input specimen had smaller grain sizes, higher microhardness and tensile properties.

A novel ultrasonic vibration assisted (UVA) wire arc additive manufacturing (WAAM) was used to fabricate Cu-8Al-2Ni-2Fe-2Mn alloy in this study. The effect of different interpass temperatures with and without ultrasonic vibration on the microstructural evolution and mechanical properties of the fabricated part were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), nanoindentation, and mechanical tensile testing. The results showed that reduction of the interpass temperature without UVA treatment cannot prevent the columnar dendrites directionally growing along the deposition direction. Under the UVA treatment, the coarse columnar dendrites were broken at the interpass temperature of 400 °C, and formed a fine cellular structure with an interpass temperature of 100 °C, owing to the acoustic streaming effect and cavitation effect. In addition, globular κII phase was based on Fe3Al and lamellar κIII phase was based on NiAl distributed in the interdendritic region, whereas κIV phase (rich-Fe) were precipitated in the α-Cu matrix. The improvement of microstructural characteristics caused by UVA treatment further improved the tensile properties and nano-hardness of WAAM fabricated parts. Eventually, it is experimentally demonstrated that WAAM fabricated Cu-8Al-2Ni-2Mn-2Fe alloy can obtain high-performance at UVA process under an interpass temperature of 100 °C.

Wire arc additive manufacturing (WAAM) is successfully applied to the manufacturing of Cu-8Al-2Ni-2Fe-2Mn nickel aluminum bronze alloy. The effects of deposited height on microstructure, tensile properties and microhardness are investigated. Results show that the differences in mechanical properties are related to microstructure anisotropy. The microstructure of the as-deposited condition mainly consists of dendrite, cellular grains, columnar dendrites and equiaxed dendrites. With the increase in height of the deposited wall, the width of the primary dendrite arm spacing successively increases. The microhardness and tensile testing results are differently influenced by the microstructure with the change in positions. The tensile properties, including the ultimate tensile strength and elongation, exhibit anisotropy in the horizontal and vertical directions. The results are explained in detail through temperature field measurement and digital image correlation system. The findings indicate that WAAM is a feasible method to obtain nickel aluminum bronze alloys despite of that fact of anisotropic mechanical characteristics.

In this paper, the wavelet decomposition of the electrochemical noise was successfully applied to derive the wavelet noise resistance (R-cd), which was further used to assess the corrosion behavior of Q235 mild steel in the simulated corrosion atmosphere (the salt spray test with 0.01 and 0.1 mol/L NaCl). The noise signatures, noise resistance (R-n), SEM, and XRD techniques were used as complementary measurements. The electrochemical noise data were acquired from two identical working electrodes by the zero resistance ammeter (ZRA) mode. The experimental results of the noise signatures and R-n indicated that the corrosion rate increased with the exposure time in the early stages of atmospheric corrosion. The analysis of the surface corrosion morphology and R-n showed a higher corrosion rate at a higher concentration of spraying solution. Also, the values of R-n and R-cd closing to the 2 Hz corroborate well in both simulated corrosion atmospheres. The wavelet noise resistance is an effective method for the analysis of the atmospheric corrosion damage of Q235 steel in the marine environment.

采用电弧增材制造技术,研究不同层间温度下有无超声振动对电弧增材制造Cu-8Al-2Ni-2Fe-2Mn合金组织及拉伸性能的影响.结果表明:在电弧增材制造的过程中,控制不同的层间温度不能抑制外延生长的柱状枝晶形成,引入超声振动后,在层间温度100℃下获得胞状晶组织.电弧增材制造的Cu-8Al-2Ni-2Fe-2Mn合金主要由枝晶间的κII相(Fe 3 Al)和κIII相(NiAl)以及在α-Cu基体中析出的κIV相(富铁)组成.在含有柱状枝晶的试样中,拉伸性能均存在各向异性.在引入超声振动+层间温度100℃的试样中,各向异性较小并获得最佳综合拉伸性能.通过引入超声振动和控制层间温度,优化组织和拉伸性能,为高性能铝青铜合金的快速制造提供潜在方案.

In order to investigate the microstructure and mechanical property evolution of low-carbon reduced activation ferritic/martensitic（RAFM） steel during isothermal aging, the normalized and tempered specimens were aged at 600 °C for 500,1000, and 3000 h, respectively. The microstructural evolution with aging time was analyzed, including the precipitation and growth of M 23 C 6 and MX-type carbides as well as the formation of Laves phase. The results indicate that the coarsening of M 23 C 6 is more obvious than that of MX with increase in aging time. During the long-term thermal exposure, the Fe 2 W Laves phase precipitates adjacent to M 23 C 6 along the prior austenite grain boundaries and packet boundaries. Lower carbon content can delay the precipitation of Laves phase compared to the steel containing higher carbon. In addition, the Laves phase precipitated along boundaries can provide the precipitation strengthening, slightly increasing the tensile strength of low-carbon RAFM steel after aging for 3000 h.