Transient liquid phase bonding of DD5 superalloy using a designed interlayer: microstructure and mechanical properties

Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines.However,metallurgical defects during the manufacturing process and damage during harsh environmental service are inevitable challenges for turbine blades.Therefore,bonding techniques play a very important role in the manufacturing and repair of turbine blades.The transient liquid phase(TLP)bonding of DD5 Ni-based single crystal superalloy was performed using the designed H1 interlayer.A new third-generation Ni-based superalloy T1 powder was mixed with H1 powder as another interlayer to improve the mechanical properties of the bonded joints.The res-ults show that,such a designed H1 interlayer is beneficial to the improvement of shear strength of DD5 alloy bonded joints by adjusting the bonding temperature and the prolongation of holding time.The maximum shear strength at room temperature of the joint with H1 interlayer reached 681 MPa when bonded at 1260℃for 3 h.The addition of T1 powder can effectively reduce holding time or relatively lower bond-ing temperature,while maintaining relatively high shear strength.When 1 wt.%T1 powder was mixed into H1 interlayer,the maximum room temperature shear strength of the joint bonded at 1260℃reached 641 MPa,which could be obtained for only 1 h.Considering the bonding temperature and the efficiency,the acceptable process parameter of H1+5 wt.%T1 interlayer was 1240℃/2 h,and the room tem-perature shear strength reached 613 MPa.

Microstructure - properties relationship of transient liquid phase diffusion bonded a third generation single crystal super alloy joint

Microstructure of transient liquid phase( TLP) diffusion bonded a third generation single crystal superalloy joint was investigated using scanning electron microscopy( SEM),and mechanical properties test of joint was carried out,for obtaining relationship between microstructure and mechanical properties of joint. The results showed that the joint contained bonding zone and base metal. The diffusion zone was obviously observed. When it was not finished for isothermal solidification process,the bonding zone would contain isothermal solidification zone and rapid solidification zone. Metallographic examination revealed that isothermal solidification zone was consisted of γ and γ' phase. Rapid solidification zone was consisted of two different structures,which were ternary eutectic of borides,γ and γ' phase developing at the edge of joint,binary eutectic of γ and γ' phase appearing in the portion of joint. When it was not enough for homogenization process under the condition of finishing isothermal solidification process,the bonding zone would contain isothermal solidification zone and borides at the interface. Under the conditions of relatively high welding temperature and long welding time,average tensile strength of joint was equivalent to that of parent material.

Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).

Formation process, microstructure and mechanical property of transient liquid phase bonded aluminium-based metal matrix composite joint

The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid diffusion (stage 1), dissolution of interlayer and base metal (stage 2), isothermal solidification (stage 3) and homogenization (stage 4). The microstructure of the joint depends on the joint formation process (distinct stages). The plastic deformation and solid diffusion in stage 1 favoure the intimate contact at interfaces and liquid layer formation. The microstructure of joint consists of aluminium solid solution, alumina particle, Al 2Cu and MgAl 2O 4 compounds in stage 2. The most pronounced feature of joint microstructure in stage 3 is the alumina particle segregation in the center of the joint. The increase of joint shear strength with increasing bonding temperature is mainly attributed to improving the fluidity and wettability of liquid phase and decreasing the amount of Al 2Cu brittle phase in the joint. The principal reason of higher bonding temperature (>600 ℃) resulting in lowering obviously the joint shear strength is the widening of alumina particle segregation region that acts as a preferential site for failure. The increase of joint shear strength with increasing holding time is mainly associated with decreasing the amount of Al 2Cu brittle phase and promoting homogenization of joint.

Interfacial Microstructure and Properties of Ti(C, N)/Ni Bonded by Transient Liquid-phase Diffusion

Effects of the main process parameters（temperature and time） on microstructure and properties of Ti（C, N）/Ni interface bonded by （Cu＋Nb） interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3Nb metallic compound and eutectic of Ni3Nb ＋ CuNiss, and finally transformed to （Ti, Nb） （C, N）＋Ni3Nb near Ti （C, N） and NiCuss ＋ Ni3Nb near Ni when diffusion bonding temperature was 1 523-1 573 K. It was clear that Cu was a constituent in the transient liquid phase （TLP） into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti （C, N） conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little （Ti, Nb） （C, N） solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3Nb accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53 mm/s^1/2.

Modulating Co-Co bonds average length in Co_(0.85)Se_(1-x)S_(x) to enhance conversion reaction for potassium storage

While alloying transition metal chalcogenides(TMCs)with other chalcogen elements can effectively improve their conductivity and electrochemical properties,the optimal alloying content is still uncertain.In this study,we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage.According to density function theory calculations,appropriate S-doping in Co0.85Se(Co_(0.85)Se_(1-x)S_(x))can reduce the average length of Co-Co bonds because of the electronegativity variation,which is thermodynamically favourable to the phase transition reactions.The optimal Se/S ratio(x=0.12)for the conductivity has been obtained from experimental results.When assembled as an anode in potassium-ion batteries(PIBs),the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance.The rate performance(229.2 mA h g^(-1)at 10 A g^(-1))is superior to the state-of-the-art results.When assembled with Prussian blue(PB)as a cathode,the pouch cell exhibits excellent performance,demonstrating its great potential for applications.Moreover,the stepwise K+storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques.Hence,this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.

PREPARATION AND EVALUATION OF HPLC BONDED PHASE WITH L-PROLINE LIGAND

This paper describes a simple method for the preparation of L-proline stationary phase bonded to silica gel and characterization of the bonded phase by IR spectrometry, elemental analysis and nitrogen adsorption method at low temperature.The enantiomeric resolutions of 3-(2-pyridyl)-3-aminopropionic acid and 2,3-diaminobutanoic acid on the bonded phase were carried out.

Studies on Synthesis of Stationary Phase Containing Nicotinamide Adenine Dinucleotide(NAD) Bonded to Phospholipid-Coated Aminated Silica for HPLC

Recently biospecific affinity chromatography has been widely used for the separation and purification of various enzymes and nucleic acids. In this paper, a series of synthetic reactions of solid-liquid phase were carried out on silica surface, using a macroporous(30 mu m), microspherical silica (8 mu m) as the matrix and gamma-aminopropyltriethoxysilane as the activating agent, the nicotinamide adenine dinucleotide(NAD) was bonded through its amino groups to the carboxylic groups of linked phospholipid which was bonded covalently on aminated support. The bonded stationary phase has high thermal stability, and could be used to separate of nucleotides with good resolution.

Influence of basicity and temperature on bonding phase strength,microstructure,and mineralogy of high-chromium vanadium–titanium magnetite

To develop a smelting process for the comprehensive utilization of high-chromium vanadium-titanium magnetite(HCVTM),the micro-sinter test was applied to investigate the influence of basicity and temperature on the HCVTM sinters.The bonding phase strength(BS) was tested via an electronic universal testing machine.The phase transformations of the HCVTM sinters were detected via X-ray diffraction(XRD),whereas the structure and mineralogy of the HCVTM sinters under different temperatures and basicities were detected via scanning electron microscopy in combination with energy-dispersive spectroscopy(SEM–EDS).Our results demonstrate that the BS of the HCVTM sinters exhibits a slightly increasing tendency with an increase in temperature when the basicity is 2.4 and within the range of 2.8–4.0.Many cracks,small size crystals,and dependent phase structures are generated by increasing the sinter basicity.The BS is lower than 4000 N when the basicity is 2.2 and 2.8.When the temperature is in the range of 1280–1300?C,the BS exceeds 4000 N with the basicity of 2.0,2.4,and 3.4–4.0.The pore size of the HCVTM sinters increases with the increase of the temperature.The perovskite decreases,whereas the silicate phase increases with basicity higher than 3.2.This study provides theoretical and technical foundations for the effective production of HCVTM sinters.

MOLTEN SALT PHASE DIAGRAMS CALCULATION USING ARTIFICIAL NEURAL NETWORK OR PATTERN RECOGNITION-BOND PARAMETERS PART 3.ESTIMATION OF LIQUIDUS TEMPERATURE AND EXPERT SYSTEM

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The effect of thermal cycle on joint of Ti/stainless steel phase transformation diffusion bonding

The effects of thermal cycle parameters on the tensile strength and fracture characteristics of phase transformation diffusion bonding(PTDB) joint of titanium and stainless steel (Ti/SS) were studied in this paper. With the maximum cyclic temperature of 1 173～1 223 K , the minimum cyclic temperature of 1 073～1 093 K , the heating velocity of 30～50 K/s , the cooling velocity of 15～20 K/s , the cycle numbers of 15～20 and bonding pressure is 13 MPa , the tensile strength of joint is more than 380 MPa , exceeding 80% of that of Ti.

A two-step transient liquid phase diffusion bonding process of T91 steels

In this study, a two-step heating process is introduced for transient liquid phase （ TLP） diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating step is addressed to melt the interlayer, followed by the second step to complete isothermal solidification at a low temperature. The most critical feature of our new method is producing a non-planar interface at the T9／ heat resistant steels joint. We propose a transitional liquid phase bonding of T91 heat resistant steels by this approach. Since joint microstructures have been studied, we tested the tensile strength to assess joint mechanical property. The result indicates that the solidified bond may contain a primary solid-solution, similar composition to the parent metal and free from precipitates. Joint tensile strength of the joint is not lower than parent materials. Joint bend＇s strengths are enhanced due to the higher metal-to-metal junction producing a non-planar bond lines. Nevertheless, the traditional transient liquid phase diffusion bonding produces planar ones. Bonding parameters of new process are 1 260 °C for 0. 5 min and 1 230 °C fo r 4 min.

Synthesis,Structure and Bonding Feature of New Metallic Zintl Phases RE_3Cu_3Sb_4(RE= Nd ,Sm ,Tb , Dy , Ho)

RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, space group I43d (No.220), Pearson code cI40. The unit cell parameters are: Nd 3Cu 3Sb 4: a =0 96749(1) nm, V =0 90561(3) nm 3; Sm 3Cu 3Sb 4: a =0 96145(1) nm, V =0 88875(3) nm 3; Tb 3Cu 3Sb 4: a =0 95362(1) nm, V =0 86721(3) nm 3; Dy 3Cu 3Sb 4: a =0 95088(1) nm, V =0 85975(3) nm 3; Ho 3Cu 3Sb 4: a =0 9488(2) nm, V =0 8541(5) nm 3; Z =4. The structures are characterized by covalent bonded Cu Sb tetrahedra which form three dimensional networks by sharing corners. The rare earth atoms are distributed in the cages. The formula with the charge balance can be written as RE 3+ 3Cu 1+ 3Sb 3- 4 which are metallic Zintl phases having the weak metallic conductivity. The bonds have typical transitional features. General atomic coordination environment rules are followed. The unit cell parameters show the lanthanide contraction.

Effects of nano-AlN on phase transformation of low temperature vitrified bond during sintering process

The effects of nano-AlN and sintering temperature on bending strength and wear resistance of low temperature vitrified bond for diamond grinding tools were studied. Furthermore, the phase transformation during sintering process was investigated by means of thermo-gravimetric analysis (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results show that the higher bending strength and wear resistance of low temperature vitrified bond are obtained by adding nano-AlN in bonds and sintering at optimum temperature. Nano-AlN added in bonds promotes the crystallization during sintering process and refines the grain sizes of crystalline phase.

MOLTEN SALT PHASE DIAGRAMS CALCULATION USING ARTIFICIAL NEURAL NETWORK OR PATTERN RECOGNITION-BOND PARAMETERS Part 2.Prediction of phase diagrams of ternary molten salt systems

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Transient liquid phase bonding of TiC particulate reinforced magnesium metal matrix composite (TiC_p/AZ91D)

Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times from 5 min to 50 min at bonding temperature of 510 ℃ , the average concentration of copper in the bonded zone decreased, the microstructure in the zone changed from Cu, α-Mg and CuMg2 to α-Mg, CuMg2 and TiC, and mechanical properties of the joint increased. The shear strength of the joint bonded at 510 ℃ for 50 min reached 64 MPa due to the metallurgical bonding of the joint and improving its homogeneity of composition and microstructure. It is favorable to increase the bonding time for improving mechanical properties of TLP bonded magnesium MMC joint.

Research on Steam Oxidation Resistance of Si3N4-bonded SiC Refractories

The steam oxidation of Si3N4-bonded SiC was determined at 1000℃for 50,100,150,200,250 and 300 h,respectively,according to ASTM C863-2000.The evolution of the phase composition and the microstructure as well as their relationship was investigated by XRD and SEM.The results show that the oxidation rate of Si3N4-bonded SiC is periodic.The presence of nitrogen element can impede the crystallization of SiO2 glass;the local enrichment of CaO impurities is unfavorable for the existence of fibrous SiO2.SiO2 mainly exists as cristobalite when the CaO/SiO2 ratio reaches a suitable level,but gradually transforms to quartz along with the oxidation time when the SiO2 content increases,or the CaO/SiO2 ratio decreases,due to the insufficient mineralization of CaO.The crystallization of SiO2 glass,especially the formation of quartz is the key factor leading to the volume expansion and structural stress.When the cracks extend and reach the surface,the degradation of the material accelerates.

Interfacial reactions and diffusion path in partial transient liquid-phase bonding of Si_3N_4/Ti/Ni/Ti/Si_3N_4

The interfacial reactions in partial transient liquid-phase bonding of Si3N4 ceramics with Ti/Ni/Ti interlayers were studied by means of scanning electron microscopy （SEM）, energy dispersive spectrometry （EDS） and X-ray diffractometry （XRD）. It was shown that the interfacial structure of Si3N4/TiN/Ti5Si3+Ti5Si4 + Ni3Si/ （NiTi ） /Ni3Ti/ Ni was formed after bonding. The activation energies for TiN layer and the mixed reaction layer of Ti5Si3 + Ti5Si4 + Ni3Si are 546. 8 kJ/mol and 543. 9 kJ/mol, respectively. The formation and transition processes of interface layer sequence in the joint were clarified by diffusion path. An important characteristic, which is different from the conventional brazing and soid-state diffusion bonding, has been found, i. e., during the partial transient liquid-phase bonding, not only the reaction layers which have formed grow, but also the diffusion path in the subsequent reaction changes because of the remarkable variation of the concentration on the metal side.

Bonding of Al_2O_3 ceramic and Nb using transient liquid phase brazing

The brazing of Al 2O 3 to Nb was achieved by the method of transient liquid phase (TLP) bonding. Ti foil and Ni 5V alloy foil were used as interlayers for the bonding. The base materials were brazed at 1 4231 573 K for 1120 min. The results show that the shear strength of the joint first increases and then decreases with increasing holding time and brazing temperature. The joint interface microstructure and elements distribution were investigated. It can be concluded that a composite structure, in which the base metals are solid solution Nb(V) and Nb(Ti) reinforced by Ni 2Ti, is formed when the brazing temperature is 1 473 K and holding time 15 min, and a satisfactory joint strength can be achieved. The interaction of Ti foil and Ni 5V foil leads to the formation of liquid eutectic phase with low melting point, at the same time the combination of Ti come from the interlayer with O atoms from Al 2O 3 results in the bonding of Al 2O 3 and Nb.