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In this paper, dissimilar joining of NbSS/Nb5Si3 composites to GH5188 Co-based superalloy was performed by using two commercial Ni-based brazing filler alloys, BNi-2 and BNi-5 fillers. The interfacial microstructures of the brazed joints were investigated by scanning electron microscope equipped with an X-ray energy dispersive spectrometer. Three-point bending test was also conducted. When brazed with BNi-2 filler alloy at 1020°C for 15 min, typical reaction products across the brazing seam could be identified as NiSS, borides, Ni3Si+Nb3Si, and (Nb,Ti)2Ni phase. Due to the physical and chemical mismatch between the dissimilar base materials, some cracks were observable at the NbSS/Nb5Si3 composites side. The joint strength was only 60 MPa. While brazed with BNi-5 filler alloy at 1160°C for 15 min, the interfacial reaction became more sufficient, and the joints exhibited an average bending strength of 272 MPa.

Limited strength and ductile joints for bonding γ-TiAl intermetallics are one of the main concerns on γ-TiAl applications in the aerospace industry. In this study, a new ductile brazing filler with TiZrCuNi system was developed by an established model for calculating the electrons distribution of the unit cell for the filler. Three kinds of fillers with fixed amount of Cu and Ni as 25 wt.%, but different Zr level (25, 18, 10 wt.%) were designed. It was found that the filler diffusion was affected by the filler composition, which was insufficient with high Zr content up to 37.5 wt.%. And the defects such as the voids and the cracks were observed with medium Zr level as 25 wt.% and brazing temperature as 1000 °C. The sound joints by Zr as 18 wt.% and 10 wt.% filler at 950 °C and 980 °C respectively were achieved with tensile strength as 520 MPa–570 MPa at room temperature. This tensile strength was remained as 495 MPa in average at 600 °C. The strong joints were attributed to the fine, randomly oriented Ti3Al grains and evenly distributed elements at the interfaces.

The joining of the SiCf/SiBCN composite was difficult due to the undue reactions between the SiCf/SiBCN composite and the common Ni- or Co-based filler alloy. In this paper, a new filler alloy with the nominal composition of Co-20Ni-12Pd-18Nb-15Cr (wt.%) was newly designed to join the SiCf/SiBCN composite. Compared with the BNi-5 filler alloy, the periodic banded structure in the reaction layer was eliminated. During the brazing process, the element Cr played an active role in the interfacial reactions and formed Cr23C6 layer at the surface of the SiCf/SiBCN composite. The interfacial reaction layer could inhabit the diffusion of the elements Co and Ni to the SiCf/SiBCN substrate. And then the interfacial reactions were controlled well. Under the brazing condition of 1200 °C/10 min, the average joint strength was increased from 18.2 to 54.9 MPa.

Dissimilar brazing of Ti2AlNb-based alloy and Ni-based wrought superalloy (GH536) was studied using NiCrFeSiB filler metal. The Ti2AlNb/GH536 joints were analyzed by scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The formation mechanism of interfacial microstructure and mechanical properties of Ti2AlNb/GH536 joints were studied. The results indicated that Ti2Ni(Al,Nb), AlNi2Ti and TiB2 reaction layers were formed in the joint adjacent to Ti2AlNb base metal. These layers resulted in high micro-hardness and the weak link of the joint. γ solid solution was formed through isothermal solidification and β1-Ni3Si phase precipitated in the γ solid solution during cooling process. Ni3B, β1-Ni3Si and CrB phases appeared in the centre of the joint. Blocky and needle-like borides formed within the diffusion affected zone of GH536 base alloy. The maximum tensile strength of Ti2AlNb/GH536 joints reached 425 ​MPa ​at room temperature and the strength value of 373 ​MPa was maintained at 923 ​K.

Affected by factors such as complex production operation data, high dimensions, and weak regularity, the existing ultra-short-term working condition prediction method struggles to guarantee the prediction accuracy and operation speed. Therefore, we propose an ultra-short-term working condition prediction method based on a convolutional neural network (CNN) and a long short-term memory network (LSTM). Firstly, we use sliding window and normalized processing methods to carry out data processing, and use CNN to extract the characteristics of processed production operation data. Secondly, we then improve the LSTM gated structure and introduce L2 norm, learning the change law of the production operation data by means of the LSTM prediction layer, and then obtain the predicted value of the working condition. We use the Bayesian method to select the parameters of the CNN-LSTM model to improve the prediction accuracy. Finally, we apply our method to a real-world application to demonstrate that our ultra-short-term working condition prediction method achieves superior results for prediction accuracy and running speed when compared with other methods.

Cf/SiC composites were joined to itself with (and without) Mo interlayer at 1150 °C for 10 min by Cu–Pd–V filler metal. For two kinds of the joints, after the interfacial reactions, continuous V–C layers and dispersive V–C particles were formed at surface of the joined Cf/SiC composite. It was worth noting that much more dispersive particles were formed in case of Cf/SiC–Mo–Cf/SiC joint which was favorable to the Cf/SiC joint strength. Meanwhile, when adding a Mo interlayer in Cf/SiC joint, a continuously distributed (V, Mo)–Si compounds with high melting point was formed near the Mo interface, which can strengthen the joining interface and improve the high-temperature strength. As a consequence, the joint strength at room temperature was remarkably increased to 148.9 MPa from 99.3 MPa by inserting the Mo interlayer. When tested at 800 °C, the average three-point bend strength of the joints was improved to 120.1 MPa, nearly twice of that without Mo interlayer.

New filler alloy composition of Ti66-Ni22-Nb12 (at.%) was designed for NbSS/Nb5Si3 composite joining and the brazing experiment was conducted at 1200 °C and 1260 °C, respectively. Compared with the previously reported Ti-Ni-Nb system filler alloys, the concentration of Ni was significantly decreased from 40 at.% to 22 at.%. The filler alloy was fabricated into brazing foils by rapid solidification technique, with about 60 μm thickness. The brazing seam mainly consisted of Nb solid solution, (Nb,Ti)5Si3 and residual NiTi2 phases. Due to the high content of stabilization element Ti in the filler alloy, hexagonal γ-Nb5Si3 phase was detected in the brazing seam. When increasing brazing temperature or prolonging brazing time, the amount of residual NiTi2 phase within the joint was gradually decreased. The joints brazed at 1260 °C for 60 min exhibited three-point bend strength of 317 MPa

PurposeConstruction projects have become increasingly long, complex and costly with waste and inefficiencies and often fail to achieve the desired results. Integrated project delivery (IPD) is believed to change these problems. A reasonable and fair profit distribution mechanism is a critical factor for ensuring the success of the IPD projects. This study aims to investigate the strategies of all participants in the profit distribution of an IPD project with respect to the factor of the effort level.Design/methodology/approachThis study describes the influence of owners and participants on profit distribution due to their respective efforts in the IPD project alliance. The influence of effort level on profit distribution is discussed based on the Holmstrom-Milgrom model of asymmetric information game theory and principal-agent theory, combined with incentive compatibility (IC) constraints and individual rationality (IR) constraints.FindingsThe results show that the optimal level of effort by each participant optimizes the profit distribution of an IPD project. At the same time, in the revenue incentive contract, the effort level of the participants is positively correlated with the profit distribution, proportional to their contribution coefficient and inversely proportional to the square of the cost of their creative activities in terms of effort. Each party of an IPD project can adopt a series of measures to improve their own effort level and choose the optimal level of effort based on the profit distribution, while satisfying their own utility maximization.Originality/valueThis study introduces the Holmstrom-Milgrom model in the principal-agent theory to explore the influence of the effort level on profit distribution in IPD projects. The quantitative model can contribute to establish a fair and efficient profit distribution scheme for the IPD projects.

Ti-16.5Zr-13.5Cu-8.5Ni (wt.%) as a filler and brazing process as 950 °C/60 min were supplied in this study for brazing cast TiAl alloys with fully lamella structure. The interface microstructure and element diffusion were analyzed and measured by SEM, EBSD, and EPAM. And the mechanical properties of joints were evaluated. The sound joints were achieved with strength as 575 MPa at room temperature and remained as 410 MPa and 385 MPa in average at 700 °C and 760 °C, respectively. It was attributed to lots of fine grains with soft orientation as BCC [120] in the joint to the tensile direction. It was found that the fracture happened in the local zones with very large grains and the extreme misorientation between grains in the joint. Even though most grains as Ti3Al phase were found in the joint, there was no sign indicating the formed IMC related to the fracture.

For the purpose of high-temperature service potential and the weight reduction expectation in aviation engineering applications, dissimilar joining of TiAl alloy to Ni-based superalloy has been conducted with a newly designed Fe-based filler metal. The microstructure and chemical composition at the interfaces were investigated by SEM, EPMA, and XRD. The filler metal consisted of Fe-based solid solution and a small amount of precipitated (Fe, Cr)ss. The wettability experiment results showed that the filler metal presented a stronger reaction tendency and more sufficient spreading behavior on Ni-based superalloy than on TiAl alloy. The brazed joint was composed of TiAl diffusion affected zone, Ni3Al, TiCo, borides, (Ni, Fe, Co, Cr)ss, and γ-TiAl dissolved with Ni. A stronger reaction tendency occurred between Ni and TiAl substrate due to the lower dissolution enthalpies of element Ni in melts of Ti and Al. The joints brazed at 1180 °C/5 min presented a shear strength of 267 MPa at room temperature.

Three compositions of Ag-Cu-In-Ti system brazing alloys were designed for joining SiO2f/SiO2 ceramic composite to Nb metal. The wettability of the three alloys on the composite was studied with the sessile drop method. The results showed that after heating at 1073 K for 30 min, they exhibited contact angles of 74°, 83° and 86°, respectively. The brazing alloys were fabricated into foils by rapid solidification technique. Among the three brazing filler alloys the joints brazed with AgCu-10In-5Ti at 1073 K for 10 min presented the maximum average shear strength of 30.9 MPa. During the brazing process the active element Ti diffused strongly from the filler alloy to the composite surface and a reaction layer with a thickness of 2–3 μm was formed. Sound metallurgical bonding was also achieved at the Nb side. The interface structure of the joint brazed with the AgCu-10In-5Ti alloy can be described as the following sequence: SiO2f/SiO2→SiO2+Cu3Ti3O→SiO2+TiO+Ti5Si4→Ag(s, s)+(Cu-Ti)→Nb. However, for the filler alloy with 4.0 wt% Ti content the joint strength was only 15.8 MPa.

In this study, brazing experiments were carried out on 6063 aluminum alloy using Al-20Cu-5Si-2Ni filler alloy. Microstructure, mechanical property, and removing behavior of oxide film of the brazed joints were analyzed. The results revealed that the 3% (CsF-AlF3) + 97% (KF-AlF3) non-corrosive flux showed high activity, especially effective removal of oxide films during the brazing process. For the brazing condition of 580 °C/10 min, the brazing seam contained less CuAl2 intermetallic compared with that of 570 °C/20 min and presented a higher shear strength of 126.1 MPa at room temperature. After heat treatment the joint strength was increased to 156.5 MPa. Furthermore, the heat-treated joints subjected to a salt spray test still retained a shear strength of 150.2 MPa.

For high-temperature joining of SiC ceramics, a multi-element AuPdCoMnNi alloy was designed and used as filler metal to join SiC ceramics to metal Mo. The brazing experiment was conducted under the condition of 1150 °C for 5 min and 10 min, respectively. The results show that numerous micro-cracks are visible in the directly brazed Mo/SiC joints, which are continuously distributed in bands of (Co, Ni)-Si and (Pd, Ni)2Si compounds. SiC was further joined to Mo using a Kovar interlayer under the same brazing conditions, and the metallurgical quality of the joints was evidently improved compared with the joints without this interlayer. The joining layer was mainly composed of (Au, Mn)ss layer mixed with element C, (Fe, Co, Ni, Mo)-Si compound layer and (Fe, Co, Ni)-Si compound with discontinuous (Pd, Ni)2Si phases and some small fragments of (Fe, Co, Ni, Mo)-Si compounds. In addition, the shear strength of the joints with Kovar interlayer reaches 55.36 MPa, remarkably higher than the void. The joining mechanism was also discussed.

Joining of Ti2AlNb alloy to TiAl intermetallics was conducted by the newly-developed Ti–Ni–Nb–Zr brazing filler alloy. The microstructure evolution of the joints was investigated by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electron backscatter diffraction (EBSD). The macro-micro mechanical properties were studied by shear test and nano-indentation test. Typical interfacial microstructures across the brazing seam were Ti2AlNb substrate, α2-Ti3Al+β-Ti, γ-TiAl+Ti2Ni+TiNi+α2-Ti3Al, α2-Ti3Al+β-Ti, TiAl substrate. The Ti2Ni phase were firstly dissolved in the joints brazed at 1000 °C for 10 min and then precipitated after a prolonged holding time of 15 min. The nano-indentation test revealed that Ti2Ni phase exhibited the highest hardness of 12.60 GPa. The joints brazed at 1000 °C/15 min presented the maximum shear strength of 271 MPa. The dissolution and precipitation behavior of Ti2Ni phase was also discussed.

Joining of Cf/SiBCN composite was conducted by a newly designed Ni-Cr-Pd(Si,B) system filler alloy. The dynamic wettability on the Cf/SiBCN composite was measured by the sessile drop method. The joint microstructure and the fracture surface were analyzed by scanning electron microscope and x-ray diffraction spectrometer. The results showed that the Ni-Cr-Pd(Si,B) filler alloy exhibited a low contact angle of 11.6° on the composite after holding at 1170 °C for 30 min. Element Cr played an active role in the interfacial reaction, and a Cr7C3 reaction layer with a thickness of 8 µm was formed at the surface of the Cf/SiBCN composite. Under the brazing condition of 1170 °C for 10 min, the joint strength at the room temperature reached 66.8 MPa. When the test temperature increased to 600 and 800 °C, the joint strength was even elevated to 90.3 and 81.2 MPa, respectively. The joint strength at high temperature was higher than that at room temperature, and this should be attributed to the improvement of the joint plasticity and the release of the residual thermal stresses within the brazed joint.

For the purpose of high-temperature service and the weight reduction in aviation engineering applications, the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy (GH536) was conducted using Au-17.5Ni (wt%) brazing filler metal. The microstructure and chemical composition at the interfaces were investigated by scanning electron microscope, X-ray diffraction and transmission electron microscope. The diffusion behaviors of elements were analyzed as well. The results indicated that the Ti3Al/GH536 joint microstructure was characterized by multiple layer structures. Element Ni from Au-Ni filler metal reacted with Ti3Al base metal, leading to the formation of AlNi2Ti and NiTi compounds. Element Ni from Ti3Al base metal reacted with Ni and thus Ni3Nb phase was detected in the joint central area. Due to the dissolution of Ni-based superalloy, (Ni,Au) solid solution ((Ni,Au)ss) and Ni-rich phase were visible adjacent to the superalloy side. The average tensile strength of all the joints brazed at 1253 K for 5–20 min was above 356 MPa at room-temperature. In particular, the joints brazed at 1253 K/15 min presented the maximum tensile strength of 434 MPa at room-temperature, and the strength of 314 MPa was maintained at 923 K. AlNi2Ti compound resulted in the highest hardness area and the fracture of the samples subjected to the tensile test mainly occurred in this zone.

With assistance of Mo interlayer, joining of Cf/SiC composite to GH783 superalloy was carried out using NiPdPtAu-Cr filler alloy. Under the brazing condition of 1200 °C for 10 min, the maximum joint strength of 98.5 MPa at room temperature was achieved when the thickness of Mo interlayer was 0.5 mm. Furthermore, the corresponding joint strength tested at 800 °C and 900 °C was even elevated to 123.8 MPa and 133.0 MPa, respectively. On one hand, the good high-temperature joint strength was mainly attributed to the formation of the refractory Mo-Ni-Si ternary compound within the joint. On the other hand, the residual Mo interlayer as a hard buffer, can release the residual thermal stresses within the dissimilar joint. The Cf/SiC-Mo bonding interface was still the weak link over the whole joint, and the cracks propagated throughout the whole reaction zone between the Cf/SiC composite and the Mo interlayer.

A Ti-Zr-Fe brazing alloy was designed and fabricated into foils by rapid solidification technique for joining of TiAl-based alloy. The phase characteristics of typical joint interface microstructure were analyzed, and the influence of process parameters on the interfacial microstructure and mechanical properties was discussed. The results showed that the joint interface consists of Ti2Al, Ti3Al (Zr, Fe), Ti-based solid solution, and (Ti, Zr)2Fe phase enriched with 10.0~15.0 at.% Al. Under the brazing condition of 1283 K/10 min, the joints exhibited a shear strength of 221.3 MPa. The joint showed a brittle fracture and the fracture propagated through the entire brazing seam.

Diffusion bonding of refractory Nb–Si-based alloy was performed with Ni/Al and Ti/Al nanolayers under the condition of 1473 K/30 MPa/60 min. The NbSS/Nb5Si3 in situ composite with the nominal composition of Nb–22Ti–16Si–3Cr–3Al–2Hf was used as the parent material. The joint microstructures were examined by using a scanning electron microscope equipped with an X-ray energy dispersive spectrometer. Shear test was conducted for the bonded joints at room temperature. Within the joint bonded with Ni/Al multilayer, element diffusion occurred between the base metal and the nanolayer, with the reaction products of AlNb2 + Ni3Al, NiAl and AlNi2Ti phases. The average shear strength was 182 MPa. While using Ti/Al multilayer, the interface mainly consisted of TiAl, (Ti,Nb)Al and (Ti,Nb)2Al phases, and the corresponding joints exhibited an increased strength of 228 MPa. In this case, the fracture mainly took place in the TiAl phase and presented a typical brittle characteristic.

Recent efforts and advances in additive manufacturing (AM) on different types of new materials are presented and reviewed. Special attention is paid to the material design of cladding layers, the choice of feedstock materials, the metallurgical behavior and synthesis principle during the AM process, and the resulted microstructures and properties, as well as the relationship between these factors. Thereafter, the trend of development in the future is forecasted, including: Effects of the particles size and size distribution of powders; Approaches for producing fine microstructures; Opportunities for creating new materials by AM; Wide applications in reconditioning of damaged components; Challenges for deep understanding and applications of the AMed new materials. The idea of “Develop Materials” or “Create Materials” by AM is highlighted, but a series of scientific, technological and engineering problems remain to be solved in future.

This paper proposes an exploratory study on the preparation of titanium-based superalloys through the Ti+Al+Ti2AlNb three-component hybrid hot press sintering method. Through the hot press sintering experiment of the mixed powder under different heating and sintering processes, the plastic deformation behavior of the material is carried out on this basis Research, preliminarily discuss the constitutive relationship of the new high-temperature titanium alloy Ti-Al-Nb, establish the hot working map and recrystallization model.

Electron beam directed energy deposition (EB-DED) is a promising manufacturing process for the fabrication of large-scale, fully dense and near net shape metallic components. However, limited knowledge is available on the EB-DED process of titanium alloys. In this study, a near-α high-temperature titanium alloy Ti60 (Ti-5.8Al-4Sn-4Zr-0.7Nb-1.5Ta-0.4Si) was fabricated via EB-DED. The chemical composition, microstructure, tensile property (at room temperature and 600 °C), and creep behavior of the fabricated alloy were investigated and compared with those of the conventional wrought lamellar and bimodal counterparts. Results indicated that the average evaporation loss of Al and Sn was 10.28% and 5.01%, respectively. The microstructure of the as-built alloy was characterized by coarse columnar grains, lamellar α, and the precipitated elliptical silicides at the α/β interfaces. In terms of tensile properties, the vertical specimens exhibited lower strength but higher ductility than the horizontal specimens at both room temperature and 600 °C. Furthermore, the tensile creep strain of the EB-DED Ti60 alloy measured at 600 °C and 150 MPa for 100 h under as-built and post-deposition STA conditions was less than 0.15%, which meets the standard requirements for the wrought Ti60 alloy. The creep resistance of the EB-DED Ti60 alloy was superior to that of its wrought bimodal counterpart.

TA15 alloy with near α microstructure offers excellent high temperature mechanical properties for future gas turbine blades. To developing for the thin-wall and complex structure of this material, brazing is preferred. However, a new brazing material and process are required. In this study, a new theoretical modeling approach for designing Ti-based filler material for TA15 is presented by simulation on the bond strength in the crystal unit for the brazing filler material (BFM). The BFM chemical composition was determined as Ti-(17∼19)Zr-15Cu-15Ni wt.% to balance its strength, the toughness and relative lower melting temperature for TA15. All the fracture happened in the matrix rather than the brazing joints. It means that the strength of the brazed TA15 joint at room temperature was at least as strong as that of the matrix. Furthermore, under its service temperature (600℃), the strength of the brazing joint maintained almost 70 % of strength. The high joint strength and the ductile connection were attributed to the formed Widmanstatten structure and the sufficient diffusion of Cu and Ni solutes from the BFM across the interface. No intermetallics compound was formed in the joint. This model is established to optimizing a Ti-based filler material for achieving the excellent properties of brazed joints.

Wire-fed electron beam directed energy deposition (EB-DED) is gaining increasing attention owing to its significant advantage of producing high-quality, large-scale metallic components. In this study, EB-DED of a near-α titanium alloy (Ti–6Al–2Zr–1Mo–1 V) was conducted, and the effect of post-deposition single annealing treatment on the microstructure, texture, and anisotropy of the tensile properties was investigated. Optical microscopy, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and X-ray diffraction were employed to study the microstructure and texture characteristics. The tensile properties along the vertical (Z axis) and horizontal (Y axis) directions were evaluated at both room temperature and 500 °C. The results indicated that the prior β grains had a strong β texture along the grain growth direction. Although the α variant selection occurred in some micro-regions, the overall α phase texture was weak. In terms of tensile properties, the vertical specimens exhibited lower strength but higher ductility than the horizontal specimens at both room and elevated temperatures. The anisotropic elongation results from the directional columnar prior β grains and continuous grain boundary α phase, which facilitated the intergranular cracking. The tensile strength and ductility were simultaneously enhanced by annealing at 950 °C for 2 h to meet the standard requirements for wrought counterparts. Moreover, the anisotropy of the tensile properties was decreased significantly. The enhanced and isotropic mechanical properties can be attributed to the combined effect of the bi-lamellar microstructure and discontinuous grain boundary α phase.

Dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy has been conducted using Ag-21Cu-25Pd filler metal. The joint microstructures were analyzed using SEM, EPMA, XRD and TEM. The reaction behaviors between different elements were discussed. Due to the strong affinity, element Pd mainly reacted with Ti3Al substrate and formed intermetallic compounds of TiPd, Ti3Pd5 and AlPd. Elements Ni and Ti reacted with each other and caused the formation of Ni3Ti in the centre of the joint. Owing to the diffusion effect, element Ag was enriched in the joint central area as (Ag,Cu)ss. With the prolonging of the brazing time varying from 3 min to 15 min at 1253 K, the tensile strength of the joint firstly increased and then decreased. The joints brazed at 1253 K for 10 min presented the maximum strength of 404 MPa at room temperature, and the joint strength of 212 MPa was maintained at 773 K. The total fracture surface covered the most of the reaction zones from the (Ag,Cu)ss to the diffusion effect zone at the Ti3Al side.

Two compositions of CuPd-V system filler alloy were designed for joining the Cf/SiBCN composite. Their dynamic wettability on the Cf/SiBCN composite was studied with the sessile drop method. The CuPd-8V alloy exhibited a contact angle of 57° after holding at 1170 °C for 30 min, whereas for CuPd-13V alloy, a lower contact angle of 28° can be achieved after heating at 1200 °C for 20 min. Sound Cf/SiBCN joints were successfully produced using the latter filler alloy under the brazing condition of (1170-1230)°C for 10 min. The results showed that the active element V strongly diffused to the surface of Cf/SiBCN composite, with the formation of V2C/VN reaction layer. The microstructure in the central part of the joint brazed at 1200 °C was characterized by the V2C/VN particles distributing scatteringly in CuPd matrix. The corresponding joints showed the maximum three-point bend strength of 82.4 MPa at room temperature. When the testing temperature was increased to 600 °C, the joint strength was even elevated to 108.8 MPa. Furthermore, the joints exhibited the strength of 92.4 MPa and 39.8 MPa at 800 °C and 900 °C, respectively.