Abstract: Three different approaches for metal to ceramic brazing are compared using the example of
Si3N4/TiN-steel joints: the use of an active filler metal (single layer brazing system), the
metallisation of the ceramic and brazing with a non active filler (two-layer brazing system), the use
of a composite brazing filler system (three layer brazing system). Different aspects are analysed: the
development of the joint’s microstructure in the as-brazed state, the thermally induced residual
stresses and the resulting bend strength of the joint’s strength.
With two layers and three layers brazing system, bend strength of about 400 MPa, about 15%
higher then single filler metal, were achieved. The three layer brazing system has two advantages:
firstly one step processing secondly lower scattering of joint bend strength compared to two layers
The key factors in all cases are the selection of the brazing fillers and the braze design. In all cases a
careful selection of the brazing fillers and the braze design are the key factors. The first criteria for
the selection of the brazing fillers for joints of dissimilar materials can be done by considering only
the main filler characteristics like titanium content, processing temperature and yield stress. It’s
necessary to simulate the joint behaviour by finite element simulation for verifying the final
selection of filler metals. It was clearly seen that the plasticity of the filler metal is the main factor
affecting residual stresses for the joint geometry in this current work.
Abstract: Laser-roll bonding and magnetic pulse welding are two relatively new processes
that greatly minimize problems of metallurgical incompatibilities between dissimilar metals
and alloys. These two processes, though technologically apart and invented for components
with distinct geometries, utilize to various extents high pressures to facilitate rapid and
localized interfacial heating and create reliable joints. In this paper, relations between process
parameters, microstructures, and properties are discussed for aluminum-to-steel joints made
by laser-roll bonding and magnetic pulse welding.
Abstract: In this study, 0.1~1.0 wt.% of pure Ce was added into a Sn3Ag0.5Cu solder alloy,
resulting in the formation of precipitated CeSn3 clusters of a size greater than 20 1m in the
reflowed solder matrix. After natural aging at room temperature for more than 3 days,
oxidation on the surface of the CeSn3 clusters was much heavier than in the undoped
Sn3Ag0.5Cu solder matrix. In addition, many tin whiskers with a diameter of about 0.1 to 0.3
μm had been squeezed out of the oxide layer of the CeSn3 precipitates. The increase in aging
time at room temperature causes the tin whiskers to grow rapidly. The whiskers can grow
even to a length of over 300 μm after 21 days of storage. The whisker growth rate in one
particular case reached 8.6Å/s after room temperature storage for only one day. The whiskers
formed during storage at a higher temperature (1500C have a coarse diameter of 1 to 3 μm.
In some cases, high temperature storage results in the formation of short whiskers in a hillock
shape with a diameter of about 5 to 10 μm.
Abstract: Although Friction Stir Welding (FSW) avoids many of the problems encountered when
fusion welding high strength Al-alloys, it can still result in substantial residual stresses that have a
detrimental impact on service life. An FE model has been developed to investigate the effectives of
the mechanical tensioning technique for controlling residual stresses in FSWs. The model purely
considered the heat input and the mechanical effects of the tool were ignored. Variables, such as
tensioning level, heat input, and plate geometry, have been studied. Good general agreement was
found between modelling results and residual stress measurements, justifying the assumption that the
stress development is dominated by the thermal field. The results showed a progressive decrease in
the residual stresses for increasing tensioning levels and, although affected by the heat input, a
relatively low sensitivity to the welding variables. At tensioning levels greater than ~ 50% of the room
temperature yield stress, tensile were replaced by compressive residual stresses within the weld.
Abstract: Joining technology of CP-Titanium and Titanium alloy is very important for manufacturing
field. In that case of titanium brazing, chemical compositions of brazing filler metal and brazing
atmosphere are very important. In this study, CP-Ti/CP-Ti and Ti alloy/Stainless Steel were brazed
with Ti-based laminated brazing filler metal by using continuous type furnace under Ar gas
atmosphere containing extremely low oxygen.
Laminated filler was fabricated by roll bonding technology. Chemical compositions of
laminated filler metal used in this study were Ti-15Cu-15Ni and Ti-20Zr-20Cu-20Ni. Brazing
temperature employed in this study was 850, 900, 950, and 1000 C. These brazing temperatures were
based on thermal analysis results and alpha-beta transformation temperature of the base metal used in
this study. Firstly melting properties of laminated brazing filler metal was investigated with DTA and
DSC. Secondary joint characteristics were estimated by micro-structural observation at the joint and
mechanical properties measurement.
Sound joint was obtained in this study according to outside appearance of the specimen.
Ti-20Zr-20Cu-20Ni filler had low melting point as compared with Ti-15Cu-15Ni according to
thermal analysis results and fillet form-ability. Ni and Cu were diffused from molten brazing filler to
base metal during brazing and Ti-Cu-Ni eutectoid reaction was took placed at the based metal during
cooling after brazing.
Abstract: Liquation cracking in the partially melted zone (PMZ) of aluminum welds was studied.
The PMZ is the region immediately outside the fusion zone where the material is heated above the
eutectic temperature. Highly crack-susceptible alloys 2024 and 7075 were welded using gas-metal
arc welding (GMAW) with filler metals 1100 and 4043, respectively. Circular-patch welds were
made on 3.2 mm thick workpiece with full penetration, and single-pass welds were made on 9.5
mm thick workpiece with partial penetration. Liquation cracking was observed in all welds. Dualpass
welds were also made on 9.5 mm thick workpiece, with overlapping between the penetration
tips of the two partial-penetration passes made on the opposite sides of the workpiece. Liquation
cracking was found in the first pass but not in the second pass. The results were explained using TfS
(temperature vs. fraction solid) curves of the weld metal (WM) and the PMZ based on the
following criterion proposed recently: liquation cracking can occur if WM fS > PMZ fS during PMZ
Abstract: Affection of the main process parameters(Temperature and Time) on microstructure
and properties of Ti（C,N）/Ni interface has been studied by using Cu and Nb interlayer in Vacuum
diffusion welding device. Results have shown that interface interlayer did not change and interface
microstructure was Cu/Nb layer structure and Cu diffused into Ni with a little when diffusion
welding temperature was lower than 1273K. But when diffusion welding temperature was 1523K,
interface microstructures were Ni8Nb metallic compound and dispersing deposition CuNi solid
solution in the earlier, finally they were transformed into (Ti,Nb)(C,N)+Nb7(Ni,Ti,Cu)6+NbNi3 near
Ti（C,N） and NiCu+NbNi8 near Ni. It was clear that Cu was as transition liquid which dissolved Ni
so as to forming CuNi transition liquid, so that Nb was dissolved in CuNi transition liquid rapidly.
Ti(C,N) can been wetted with creating NiNbCu transition liquid, and then, a little (Ti,Nb)(C,N)
solid solution were formed at interface so as to increasing interface combining capability. Interface
shear strength may get to 140 MPa.
Abstract: Si3N4 and 40CrMo steel was joined using Ag-Cu-Ti-Pd brazing filler. Microstructure of
the joint and bonding interface was studied by SEM and EDS, and the phase structure was analyzed
by XRD. The results indicate that reaction layers at ceramic/ filler alloy and filler alloy/steel
interfaces are formed. There is a reaction layer containing TiN and Ti5Si3 between ceramic and filler
alloy, while the reaction layer between filler alloy and steel is composed of Fe-Ti compound. The
middle part of the joint is an eutectic structure composed of Ag-riched and Cu-riched solid solutions.
With the increase of the brazing temperature, the thickness of the joint seem decrease, the thickness of
the reaction layer between Si3N4 and filler alloy increases and then decreases, and the thickness of
the reaction layer between filler alloy and steel increases.
Abstract: The diode laser brazing of heat-resistant alloys with precious brazing filler metals has
been conducted using the tandem beam consisted of preheating beam and main brazing beam.
The 1mm thick plates of Inconel 600 and A286 alloys were butt-brazed with the 0.5mm diameter
Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals using a brazing flux. The sound butt
joints which were free from brazing defects such as porosity and lack of penetration could be
obtained at the brazing clearances of 0.1-1.5mm. Fracture strength of braze joints using Au-Ni
and Ag-Cu-Pd filler metals was comparable to the base metal strength at any brazing clearance
between 0.1-1.5mm, whereas that using Ag-Pd filler metal increased with decreasing the brazing
clearance and attained about 70% of the base metal strength at brazing clearance of 0.1mm. The
computer simulations of the braze metal flowing and the base metal erosion suggested that the
preheating effect during the tandem beam brazing resulted in the superior brazability at the
narrow-gap as well as wide-gap brazing attributed to the improvement in the wetting, spreading,
infiltrativity and the erosion resistance of melted filler metal.
Abstract: The paper treats the application of laser to repair of cracks occurring at dies for die
casting of non-ferrous metals (particularly aluminium, magnesium and their alloys). The first part
describes a suitable laser unit enabling crack grooving and then welding. An Nd:YAG laser source
is shown with its equipment for laser-beam transfer, control and directing of laser-beam focus. Dies
for die casting are made of quality steels and are of very complex shape. As far as their repair is
concerned this means that they are to be welded at their edges, corners, narrow gaps and vertical
walls, i.e. in various positions and in various directions. In the second part the grooving technology
is described, and in the third part laser welding of grooved cracks using a filler material, i.e., a thin
welding wire. At the end some conclusions are drawn. It is stated that from the viewpoints of
technology and economics, it is sensible to laser groove and then weld the thermal cracks with a
suitable material. The filler material should have such a chemical composition that after welding a
weld having adequate mechanical properties, without any additional heat treatment, is obtained.