TLP bonding of dissimilar FSX-414/IN738 system with MBF80 interlayer: Prediction of solid/liquid interface location

Isothermal solidification process of a dissimilar transient liquid phase （TLP） bonding of FSX-414/MBF80/IN738 system was simulated by finite difference method. The TLP joint model was divided into two parts and a moving liquid /solid interface model was used for the parts. Diffusion equations were solved for each half of the joints simultaneously up to the end of isothermal solidification. The completion time of isothermal solidification, concentration profiles and position of the solid/liquid interface for each half were calculated. The intersection of the solid/liquid interfaces of two halves was considered the end of isothermal solidification. To obtain some required diffusion data, TLP bonding of FSX-414/MBF80/IN738 was performed at different temperature and time under vacuum atmosphere. The calculated results show good agreement with the experimental results.

Thermal Properties of Ni–Cr–Si–B–Fe Based Interlayer Material and Its Application in TLP Bonding of IN 718 Superalloy

A new Ni–Cr–Si–B–Fe fi ller material is prepared for transient liquid-phase(TLP)bonding of Inconel 718 superalloy by mechanical alloying technique.The melting temperature range of the fi ller material and its activation energy of melting are determined by diff erential scanning calorimetry technique.The activation energy and melting temperature of the alloy powder decrease with increasing milling time.Inconel 718 alloy was joined via TLP by using the newly developed fi ller material.The eff ect of TLP bonding temperature and time on microstructural evolution and mechanical properties of the joint was investigated.Three distinct microstructural regions were observed in the bonding area:isothermal solidifi cation zone consisting of a single-phase solid solution,diff usion aff ected zone consisting of extensive diff usion-induced precipitates of metallic boride,and unaff ected base material.The ultimate shear strength and microhardness of the TLP-bonded joint increase with bonding time and temperature.

Influence of the Substrate Orientation on the Isothermal Solidification during TLP Bonding Single Crystal Superalloys

Angle deviations between the two substrates during transient liquid phase （TLP） bonding single crystal superalloys cannot be avoided. In the present work, specimens have been prepared to investigate the influences of the various substrate orientations. It is found that the width of the non-isothermal solidification zone （NSZ） is linear with the square root of the isothermal solidification time. This suggests that the isothermal solidification process is B-diffusion controlled in different substrate orientation deviations. And also the width of the NSZ increases with increasing angle deviation, indicating that the isothermal solidification time needed in the TLP bonding increases with increasing orientation deviation between the two substrates.

Transient Liquid Phase Bonding of Ni-base Single Crystal Superalloy

The Ni-base single crystal superalloy was bonded by the transient liquid phase (TLP) bonding, using a Ni-base flexible metal cloth as an insert alloy. TLP bonding of superalloy was carried out at 1473-1523 K for 0.5-24 h in vacuum. The [001] orientation of each test specimen was aligned perpendicular to the joint interface. The bonded region was observed by optical microscopy, and the microstructural and compositional analyses across the bonded interlayer were performed by using a scanning electron microscopy (SEM). The electron back scattering diffraction (EBSD) method was applied to determine the crystallographic orientation. The results indicated that the chemical homogeneity across the bonded region can be achieved, and γ' phase both in the bonded interlayer and in the superalloy substrate is almost identical, while the bonded interlayer had almost matched the crystallographic orientation of the bonded substrates.

Influences of gap size and cyclic-thermal-shock treatment on mechanical properties of TLP bonded IN-738LC superalloy

Influences of gap size and cyclic-thermal-shock treatment on the mechanical properties of transient liquid phase（TLP） bonded IN-738 LC superalloy were investigated. For this purpose, TLP bonding of IN-738 LC superalloy was carried out in a vacuum furnace using powdered AMS 4777 as the filler metal. The results showed that isothermal solidified zone（ISZ） consisted of Ni solid-solution and the distribution of alloying elements was homogeneous. High hardness of HV 409 and high shear strength of 506 MPa were observed in 40 μm gap sample. Alloying elements formed γ′ precipitates and the solid-solution in the ISZ. Hardness and shear strength of bonds were reduced with increasing the gap size（in range of 40-120 μm）. The fractured surfaces of complete isothermal solidified bonds showed dimpled rupture, but athermal solidified bonds showed cleavage fracture surface. 10, 20, 30 and 40 thermal-shock cycles were applied to 80 μm gap samples, respectively. The shear strength of the bond was measured to be 268 MPa after the 40 th thermal-shock cycle. The sample with gap size of 80 μm was failed due to crack nucleation on faying surface at 45 th thermal-shock cycle. The amount of the produced brittleness due to quenching the samples in water bath was attributed to the number of thermal-shock cycles.

New insights into microstructural changes during transient liquid phase bonding of GTD-111 superalloy

The effects of joining temperature(TJ)and time(tJ)on microstructure of the transient liquid phase(TLP)bonding of GTD-111 superalloy were investigated.The bonding process was applied using BNi-3 filler at temperatures of 1080,1120,and 1160℃ for isothermal solidification time of 195,135,and 90 min,respectively.Homogenization heat treatment was also applied to all of the joints.The results show that intermetallic and eutectic compounds such as Ni-rich borides,Ni−B−Si ternary compound and eutectic-γcontinuously are formed in the joint region during cooling.By increasing tJ,intermetallic phases are firstly reduced and eventually eliminated and isothermal solidification is completed as well.With the increase of the holding time at all of the three bonding temperatures,the thickness of the athermally solidified zone(ASZ)and the volume fraction of precipitates in the bonding area decrease and the width of the diffusion affected zone(DAZ)increases.Similar results are also obtained by increasing TJ from 1080 to 1160℃ at tJ=90 min.Furthermore,increasing the TJ from 1080 to 1160℃ leads to the faster elimination of intermetallic phases from the ASZ.However,these phases are again observed in the joint region at 1180℃.It is observed that by increasing the bonding temperature,the bonding width and the rate of dissolution of the base metal increase.Based on these results,increasing the homogenization time from 180 to 300 min leads to the elimination of boride precipitates in the DAZ and a high uniformity of the concentration of alloying elements in the joint region and the base metal.

Transient liquid phase diffusion bonding of a single crystal superalloy DD6

DD6 alloy was bonded by transient liquid phase (TLP) diffusion bonding. The main compositions of the interlayer alloy employed were similar to those of the base metal, DD6, and a certain amount of element B was added as the melting point depressant. The results show that it is difficult to obtain the joints with the microstructures completely homogeneous. For the joint TLP diffusion bonded at 1290℃ for 12h, about half areas of the beam possessed a γ+γ′ microstructure, nearly identical with that of the base metal, and the other local areas consisted of γ-solution, borides, etc. Prolonging the bonding time to 24h, the inhomogeneous areas in the joint reduced, and the joint property improved. The joint stress-rupture strength at 980℃ and 1100℃ reached 90%-100% and 70%-80% of those of the base metal respectively.

Improvement of Joint Strength of SiCp/Al Metal Matrix Composite in Transient Liquid Phase Bonding Using Cu/Ni/Cu Film Interlayer

The compact oxide on the surface of SiCp/Al metal matrix composite （SiCp/Al MMC） greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface of SiCp/Al MMC by plasma erosion. Cu/Ni/Cu film of 5μm in thickness was prepared by magnetron sputtering method on the clean bonding surface in the same vacuum chamber, which was acted as an interlayer in transient liquid phase （TLP） bonding process. Compared with the same thickness of single Cu foil and Ni foil interlayer, the shear strength of 200 MPa was obtained using Cu/Ni/Cu film interlayer during TLP bonding, which was 89.7% that of base metal. In addition, homogenization of the bonding region and no particle segregation in interfacial region were found by analysis of the joint microstructure. Scanning electron microscopy （SEM） was used to observe the micrograph of the joint interface. The result shows that a homogenous microstructure of joint was achieved, which is similar with that of based metal.

Microstructures and properties of transient liquid phase diffusion bonded joints of Ni_3Al-base superalloy

An investigation of transient liquid phase (TLP) diffusion bonding of a Ni 3Al base directionally solidified superalloy, IC6 alloy, was presented. The interlayer alloy employed was Ni Mo Cr B powder alloy. The results show that the microstructure of the TLP diffusion bonded joints is a combination of γ solid solution (or a γ+γ′ structure) and borides. With the bonding time increasing, the quantity of the borides both in bonding seam and adjacent zones is gradually reduced, and the joint stress rupture property is improved. The obtained stress rupture property of the TLP bonded joints is on a level with the transverse property of IC6 base materials. [

Effect of gap size on microstructure of transient liquid phase bonded IN-738LC superalloy

In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.

Microstructural evaluation of Hastelloy-X transient liquid phase bonded joints:Effects of filler metal thickness and holding time

Transient liquid phase(TLP)bonding was investigated in Hastelloy-X samples with different filler metal thicknesses(20,35,50,65,and 100μm)and holding time(5,20,80,320,and 640 min)to obtain optimum bonding parameters.Microstructural evaluations using electron probe microanalysis(EPMA)and electron backscattered diffraction(EBSD)show that the central eutectic phases present in the athermally solidified zone(ASZ)are Ni_(3)B,Ni_(2)Si,and CrB,and the precipitates formed in the diffusion-affected zone(DAZ)are MoB,CrB_(2),and Mo_(2)B_(5).According to the results,decreasing the filler thickness as well as increasing the holding time helps realize the completion of isothermal solidification and reduction in the density of precipitates in the DAZ,leading to a joint with more uniform properties.Diffusion of boron and silicon to longer distances with increasing holding time causes the removal of Cr-rich borides in the DAZ and the formation of Mo-rich silicide at the joint interface.Decrease in hardness of ASZ and DAZ due to the elimination of brittle phases in these zones during long holding time causes more uniform hardness distribution in the joint area.The best results are obtained for the sample joined with the 35μm-thick filler metal for 640 min holding time.

Microstructural Evolution of a Ni-base Alloy DZ468 Joint Bonded with a New Co-base Filler

Ni-base alloy DZ468 has been joined by transient liquid phase bonding technique with a newly developed Co-based filler. The microstructures of the Co-base filler and the joint, the effects of heat treatment on microstructure and hardness of the joint have been investigated by various experimental methods. Results show that the Co-base filler consists of γ, M2B, M5B3 and M23B6 phases. Because of the interdiffusion between the base metal and the filler, γ, MC, M5B3 and M23B6 phases are formed in the bonding zone. And localized liquidation of substrate occurs in the diffusion affected zone, with MC and M3B2 precipitating in this area. During heat treatment, the volume of the intermetallic phases in the bonding zone resulting from incomplete isothermal solidification decreases obviously. On the contrary, the width of the diffusion affected zone increases at the solution stage and subsequently decreases at the aging stages.