Effect of parameters on interface of the brazed ZrO2 ceramic and Ti-6Al-4V joint using Ti-based amorphous filler

A commercially available Ti47 Zr28 Cu14 Ni11 (at. pct) amorphous filler foil was used to join ZrO2 ceramic and Ti-6Al-4V alloy. According to experimental observations, the interface microstructure accounts for the mechanical properties of the joints. The effects of brazing conditions and parameters on the joint properties were investigated. The joint shear strength showed the highest value of about 108 MPa and did not monotonously increase with the brazing time increasing. It was shown that decreasing of brazing cooling rate and appropriate filler foil thickness gave higher joint strength.     

Brazing of 5A01 aluminum alloy using Al-Cu-Si-Ni filler metal

The vacuum brazing of 5 A01 aluminum alloy using Al-Cu-Si-Ni filler metal was investigated at 550 ℃ and 560 ℃,respectively. Microstructure and properties of brazed 5 A01 alloy joints were investigated by tensile-shear tests and scanning electron microscopy analysis. The effects of brazing temperature and holding time on the shear strength and microstructure of the joints were studied. The results show that the different intermetallic compounds such as Al-Cu-Ni and Mg_2 Si formed in the bonding area. Shear strength increased with holding time and brazing temperature. The average shear strengths increased from 42. 3 MPa brazed at 550 ℃for 5 min to 68 MPa brazed at 560 ℃ for 15 min. Discontinuous cracks were found in the joint brazed at 550 ℃ for 5 min,and the joint showed poor shear strength. high shear strength were obtained in the joints brazed at 560 ℃ for 15 min.     

Laser-MIG Arc Hybrid Brazing-Fusion Welding of Al Alloy to Galvanized Steel with Different Filler Metals

Aluminum alloy plates were joined to galvanized steel sheets with lap joint by laser-MIG arc hybrid brazing- fusion welding with AlSi5, AlSi12, AlMg5 filler wires, respectively. The influences of Si and Mg on the microstructure and mechanical properties of the brazed-fusion welded joint were studied. The increase of Si element in the fusion weld can make the grain refined, and increase the microhardness of the fusion weld. Therefore, the microhardness in fusion weld made from AlSi12 and AlSi5 filler wires can be up to 98.4 HV0.01 and 96.8 HV0.01, which is higher than that from AlMg5 filler wire of 70.4 HV0.01. The highest tensile strength can reach 178.9 MPa made with AlMg5 filler wire. The tensile strength is 172.43 MPa made with AlSi5 filler wire. However, the lowest tensile strength is 144 MPa made with AlSi12 filler wire. The average thicknesses of the intermetallic compounds (IMCs) layer with ,AlSi5 AlSi12, AlMg5 filler wires are 1.49-2.64 μm. The IMCs layer made from AlSi5, AlSi12 filler wires are identified as FeAl2, Fe2Al5 , Fe4 Al13 and Al0.5Fe3Si0.5, that from AlMg5 filler wire are identified as FeAl2 , Fe2Al5 and Fe4Al13.     

Vacuum brazing of Si/SiC ceramic composite and Invar alloy using Ti50Cu-W filler metals

Si/ SiC ceramic composite and Invar alloy were successfully joined by vacuum brazing using Ti50Cu-W filler metals into which W was added to release the thermal stress of the brazed joint.Microstructure...     

Study on interracial structure and strength of Si3N4/Ti/Cu/Ti/Si3S4 PTLP bonding

Partial transient liquid-phase bonding （PTLP bonding） of Si3N4 ceramic with Ti/Cu/Ti multi-interlayer is performed with changing the thickness of Ti foil. The influence of Ti foil thickness on interface structure and joint strength was discussed. The joint interface structures are investigated by scanning electron microscope （SEM） and energy dispersion spectroscopy（EDS）. The results show that the maximum joint strength of 210 MPa is obtained at room temperature in the experiments. When joining temperature and time are not changed and the process of isothermal solidification is sufficient , interface structure, reaction layer thickness and isothermal solidification thickness change with the thickness of Ti foil.     

A Fe-Ni-Cr system filler metal for brazing of stainless steel

New Fe-Ni-Cr system brazing alloys were designed,in which elements Si and B as well as Cu-Ti binary alloy were added as the temperature depressants. The brazing alloys were fabricated into filler foils by a rapidly-solidifying technique. It was found that, to acquire a suitable liquidus temperature of the filler alloy, the addition of Cu-Ti binary alloy decreased the needed amount of Si and B, and it had an effecton improvement in mechanical properties of the brazed joints. Based on the results of melting and wettability experiments, one filler metal was used to join stainless steel at 1140 ℃ for 15 min. The microstructure of the joint was analyzed by means of a scanning electron microscope (SEM) equipped with X-ray energy-dispersive spectroscopy(EDS). It was found that the typical joint was mainly composed of solid solution with a small quantity of Cr-rich borides strips, Ti-rich boride blocks and Cu-rich silicide particles. The brazed joints show an average tensile strength of 270.8 MPa and an average impact toughness of 35.6 J/cm².     

Effect of Heat Input on Microstructure and Mechanical Properties of Joints Made by Bypass-Current MIG Welding–Brazing of Magnesium Alloy to Galvanized Steel

Experiments were carried out with bypass-current MIG welding–brazing of magnesium alloy to galvanized steel to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. Experimental results indicated that the joint efficiency tended to increase at first and then to reduce with the increase of heat input. The joint efficiency reached its maximum of about 70% when the heat input was 155 J/mm. The metallurgical bonding between magnesium alloy and steel was a thin continuous reaction layer, and the intermetallic compound layer consisted of Mg–Zn and slight Fe–Al phases. It is concluded that bypass-current MIG welding–brazing is a stable welding process, which can be used to achieve defect-free joining of magnesium alloy to steel with good weld appearances.     

Microstructure and properties of the joints of ZrO_2 ceramic/stainless steel brazed in vacuum with AgCuTi active filler metal

The ZrO_2 ceramic was successfully jointed to stainless steel by vacuum brazing with active filler metal. The AgCuTi active filler metal was used and the joining was performed at a temperature of 850 ℃ for 10 min. The microstructures of the joints were characterized by metallographic microscopy,scanning electron microscopy( SEM),and energy dispersive spectroscopy( EDS).Metallographic microscopy analysis shows that the morphology of the cross section was a sandwich structure and the Ti O is observed in the surface of ZrO_2/stainless steel. The diffusion and enrichment of the elements are the key roles in the brazing of ZrO_2 ceramic and stainless steel. The formation of TiCu compounds inhibited the further diffusion of titanium into stainless steel or the ZrO_2 ceramic to form TiO compound. In the experimental conditions,the average tensile strength is 80 MPa for the joint of ZrO_2 ceramic/Ag Cu Ti/stainless steel systems. A complete joint is formed between the ZrO2 ceramic and stainless steel with the leakage rate at the degree of 10~(-12) Pa·m~3/s.     

Influence of Multi-pass Friction Stir Processing on Microstructure and Mechanical Properties of Die Cast Al–7Si–3Cu Aluminum Alloy

The influence of overlap multi-pass friction stir processing on the microstructure and the mechanical properties, in particular, strength, ductility and hardness of die cast Al–7Si–3Cu aluminum alloy was investigated.It was observed that increase in the number of overlap passes friction stir processing resulted in significant refinement and redistribution of aluminum silicon eutectic phase and elimination of casting porosities. The microstructural refinement by the friction stir processing not only increases the ultimate tensile strength from 121 to273 MPa, but also increases the ductility as observed by the increase in fracture strain from 1.8% to 10%. Analysis of the fractured surface reveals that the microstructural refinement obtained by friction stir processing plays a vital role in transforming the fracture mode from completely mixed mode to the ductile mode of the fracture with increasing number of passes. The change in the size, shape, morphology and distribution of eutectic silicon particles and elimination of the porosities are the main reasons for the increases in tensile strength and ductility due to friction stir processing.     

Joint interface during arc milling brazing of aluminum alloy to low carbon steel with cutter milling at various rotation speeds

In this study, 5052 aluminum alloy and Q235 steel were joined by a new way of arc milling brazing, with the Zn15%Al filler metal and no use of flux. Effect of rotation speed on mechanical properties and microstructure of joint interface was investigated. The results show that increasing rotation speed is in favor of formation of weld and spread of filler metal on substrate. The fine grain with homogeneous composition in brazed seam can be realized by the stronger stirring in pool induced by milling at more higher rotation speed. And, a composite joint reinforced with needle-like or block-like Fe-Al-Zn intermetallic compounds(IMCs) particle can be obtained by arc milling brazing, which comes from the reaction between steel scrape and Zn-A1 filler alloy. The test on strength of joint interface shows that with the increase in rotation speed,there is a peak value in variation ranges of strength of joint interface. This is to say, when rotation speed is 2720 r·min~(-1), the strength of joint has maximum value(182.01 MPa). Moreover, a thin and discontinuous IMCs layer at joint interface can be obtained by increasing rotation speed. But at a low or high rotation speed, there also is a crack at joint interface, which weakens the strength of joint interface. Only at 2720 r·min~(-1), a good joint interface without an obvious crack can be realized.     

Bonding of Al2O3 ceramic and Nb using transient liquid phase brazing

The brazing of Al2O3 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 1423-1573 K for 1-120 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 Ni3Ti, is formed when the brazing temperature is 1473 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 Al2O3 results in the bonding of Al2O3 and Nb.     

Stirring brazing of dissimilar Al/Mg alloy without flux in air

AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.     

Microstructure characteristics and mechanical properties of steel stud to Al alloy by CMT welding-brazing process

Cold metal transfer(CMT) welding of nickel-coated Q235 steel studs with 6061 Al alloy was carried out using ER4043 as filler metal.The welding process was stable,and appearance of weld formed well without surface defect under the parameters of welding current 121 A,welding voltage 15.4 V and welding speed 6 r/min.The microstructure of filler metal was analyzed by means of scanning electron microscopy.The filler metal and 6061 Al alloy were fused to form fusion welding interface,the fusion zone had a good bonding without any micro defect.The steel stud did not melt and brazing interface was formed between the filler metal and steel stud.Two different reaction layers existed in the brazing interface,the Fe_2Al_5 layer about 10- 12 μm formed near the steel stud side,and the other layer was mainly composed of FeAl_3.Nickel-rich zone was formed in the root toe area of the fillet weld,which was mainly composed of Al_3Ni_2.The tensile tests showed that the maximum shearing strength of the joints was 129 MPa.The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl_3 were distributed continuously.     

Microstructure of reactive sintered Al bonded Si3N4-SiC ceramics

Aluminium nitride-silicon nitride-silicon carbide （AIN-Si3N4-SiC） composite ceramics were prepared to increase the bending strength and improve the phase structure of Si3N4-based ceramics. The ceramics were made by reactive sintering in N2 atmosphere at 1 360 ℃, using Al as sintering additive. The phase composing of ceramics was identified with an X-ray diffractometer and the microstructure of the materials was studied by scanning electron microscopy. The results indicate that the phase structure is affected remarkably and the interface modality is changed. The interface between Si3N4 and SiC becomes blurry and that between SiC and AlN matches more better at the same time. But the liquid-phase appears during the reactive sintering along with the addition of AI by which the melting point of Si is decreased. The appearance of liquid Si decreases the bending strength of the ceramics. Lower temperature nitrification technic was introduced to avoid the appearance of liquid-phase Si. The optimum addition of Al was investigated by XRD and SEM analysis in order to obtain the maximal bending strength of materials.     

Study of the morphology and properties of diamond joints brazed with carbide-reinforced Cu-Sn-Ti filler metal

Cu-Sn-Ti brazing filler is a new type of copper-based brazing filler for brazing diamond tools currently used in industry, but it suffers from poor wear resistance, high brazing temperature and low bond strength. This paper provides a way to improve the strength of diamond-brazed joints by adding zirconium carbide and tungsten carbide reinforcing phase particles to the Cu-Sn-Ti alloy, respectively. Diamond particles were attached to Q460 steel using Cu-Sn-Ti composite filler with the addition of...     

Microstructure and properties of continuous casting Ag-28Cu-8Sn alloy fabricated by dieless drawing

Ag-28Cu-8Sn(wt%) alloy is a widely used brittle silver-based brazing filler metal.The wire of brazing filler metal was prepared by continuous casting process and dieless drawing technology.The phase structure was measured by X-ray diffraction(XRD),and the microstructure of wetting interface,cast states,processing states and fracture morphologies were characterized by the optical microscopy(OM) and scanning electron microscopy(SEM),respectively.The electrical conductivity,hardness,tensile strength and elongation rate were tested as well.Furthermore,the solid-liquid phase temperature was measured by a differential scanning calorimeter(DSC),and the wettability of brazing filler metal was tested by spreading method.The outcomes obtained show that the as-cast microstructure is a typical three-zone structure,including region of surface fine grain,zone of columnar grain and region of center equiaxed crystal.Ag-28Cu-8Sn alloy is mainly composed of Ag-rich a-phase,Cu-rich pphase and intermediate compounds.Grain refinement appears in the cross section,as for grains of the longitudinal section,the shape is changed from ribbon to fiber to form a silk texture.The strength and hardness improve with the increase in the true strain,while the conductivity and elongation are reduced.Furthermore,the solid-phase temperature is 605.9℃,and the liquid-phase temperature is 725.1℃.The spreading area of Ag-28Cu-8Sn brazing filler metal is 174 mm~2,and the metallurgical bonding occurs between Ag-28Cu-8Sn brazing filler metal and Cu matrix.In addition,compared with cold drawing process,there are not any microcracks at the fracture morphology for the alloy fabricated by dieless drawing.The dieless drawing process overcomes some processing defects of traditional cold drawing,and the processing performance of Ag-28Cu-8Sn alloy is improved.     

A preliminary study on filler metals for vacuum brazing of Al/Ti

In this paper,nine new filler metals contained Sn and Ga based on Al-11.5Si have been designed for vacuum brazing of Al/Ti.It is found that the addition of Sn and Ga can lower the solidus of filler metal,change the structure of intermetallic compound formed in the joint during brazing,and enhance the strength of joint.But the detail mechanism need further research.     

Characteristics of TIG arc-assisted laser welding–brazing joint of aluminum to galvanized steel with preset filler powder

Tungsten inert gas(TIG) arc-assisted laser welding–brazing was used for the butt joining of 5A06 aluminum alloy to the galvanized steel by preset filler powder without groove. The spreading behavior of liquid metal on the back of the galvanized steel at different assisted welding currents was also investigated. The results show that the assisted TIG arc optimizes the interface reaction temperature, enhances the wettability of liquid metal on the steel side, and forms a sound butt joint at an appropriate welding current. A non-uniform intermetallic compound is formed at the interfacial layer, which is composed of Fe2Al5 close to the steel substrate and Fe4Al13 close to the solidified aluminum. The superior tensile strength of joint is indicated when the welding current ranges from 13 to 16 A. The average tensile strength can reach 151 MPa at the welding current of 16 A, and the corresponding fracture belongs to the ductile and brittle hybrid mode.     

Joint Characteristics and Corrosion Properties of Bypass-Current Double-Sided Arc-Welded Aluminum 6061 Alloy with Al–Si Filler Metal

Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al–Si filler wire to investigate the effect of Al–Si intermetallic compounds on the microstructure, microhardness and corrosion behavior of weld joint. Experimental results indicated that the Al_(4.5)FeSi phase in the topside of the weld joint was finer than that in the backside and newly formed phase of Al_(0.5)Fe_3Si_(0.5)was observed in the backside. The formation of reinforcing phases of Al–Fe–Si in the weld improved the microhardness of the weld by about 18%. The corrosion resistance of the weld zone was greater than that of the base metal, while the corrosion current displayed opposite, and the corrosion resistance of the weld region was better than that of the base metal.     

Microstructure of Nb／Nb5Si3 in—situ composites

The Nb-10Si(mole fraction,%)alloy was fabricated using the vacuum arc-melting method and heat-treated at 1850℃ and 1550℃ for2-100h in Ar atmosphere.The microstructure of the alloy has been investigated using Xray diffractometry(XRD),scanning electron microscopy(SEM)equipped with X-ray energy dispersive spectrometry (EDS)and transmission electrom microscopy(TEM).The results show that 1550℃,100h is an optimum heat-treatment condition to acquire the equilibruum Nb Nb5Si3 two-phase microstructure.The microstructure of Nb-10Si alloy in the as-cast condition consists of continuous Nb3Si matrix and dispersed Nb particles,which implies that th alloy is in the metastable equilibrium state.In th case of 1850℃，2h heat-treatment the Nb particles are coarsened evidently.However,in the heat-treatment condition of 1550℃ for 25-100h the growth of Nb particles in unconspicuous.After heattreated at 1550℃，Nd3Si phase transforms into the equilibrium Nb5Si3 and Nb phase with the increase of heat-treatment time gradually.TEM obsevations reveal that the interface of Nb phase Nb5Si3 phase is clean and some twins with about 10nm in width are found.