Interfacial microstructures have been investigated for the anodically-bonded joint of borosilicate glass to Kovar alloy in order to get better insight into its mechanism. SEM observations of the joint interface revealed that the applied field displaced Na and K ions from the anode-side of glass to form depletion layers of these elements. Potassium also showed a pile-up layer following the K depletion layer within the Na depletion layer. Potassium depletion layer appeared as a zone darker than the bulk glass with a clear contrast. The thickness of alkali-depletion layers increased with the increase in bonding time, and then approached a saturation value. From the estimated activation energies of growth of Na and K depletion layers, it is suggested that the growth of Na and K layers is controlled by the diffusion of No. TEM observations revealed the formation of an amorphous reaction layer of about 0.1μm thickness, which consisted of a complex oxide of iron and silicon. An iron-rich crystalline layer of about 10 nm thickness was also observed between the amorphous reaction layer and the Kovar alloy substrate. The results of the present study are discussed on the basis of elements migration under the influence of electric fields generated in the glass.
In laser welding a shielding gas plays very important role to obtain high quality welds. Especially Ar shielding gas has come into wide use, but it has the problem of plasma generation in high power laser welding. This paper describes the formation of shielding gas plasma and its behavior. The authors observed plasma and molten pool directly by CCD camera, and detected the spectrum emission, acoustic emission and plasma potential at the same time. The plasma potential in this study was the potential difference between the insulated nozzle and specimen. It was generated from the difference between the mobility of electrons and the metallic ions. As for the direct observation of welding zone by CCD camera, both plasma and molten pool were seen in one flame picture by using the 25W-Ar-laser back light and original band pass filter which transmitted Ar laser light and partially plasma light pass. For optical signal, the spectrum emission of Iron atom (298.4 nm) which is representation of metallic plasma behavior and that of Ar atom (738.4 nm) were detected. According to these results, an optimum conditions for Ar shielding gas velocity and mixed ratio of shield gas were proposed. This work was performed under the management of ALERI (Applied Laser Engineering Research Institute) as a part of "the Leasing Basic Research Practical Use of Research Facility Centers" supported by NEDO (New Energy and Industrial Technology Development Organization).
The authors are researching the plasma behavior in laser welding and the applicability to monitoring. In the first paper we described the relation between the monitoring signals and shielding gas plasma. This paper describes the appearances of detective signals with changes of basic welding conditions, main results are as follows; 1. Amplitude of each signal showed more correlative with penetration depth than average of signals. 2. The correlation between an amplitude of each signal and welding condition was based on a plasma fluctuation which is influenced by the size of key hole and molten pool. This work was performed under the management of ALERI (Applied Laser Engineering Research Institute) as a part of "the Leasing Basic Research Practical Use of Research Facility Centers" supported by NEDO (New Energy and Industrial Technology Development Organization).
We are researching the plasma behavior in laser welding and the applicability to monitoring. We reported the direct observation method for laser welding and clarifying the formation of shield gas plasma by detective signals in the first paper. And we reported the appearances of the detected signals with laser welding conditions in the second paper. This paper describes the correspondence of the directive signals to the bead on plate with artificial defects. The main results are as follows; ⋅The signals of spectrum emission and plasma potential changed their wave form at touched together stainless plates. ⋅The combination of the signals from the spectrum emission and plasma potential gave more definite information on the welding abnormality, such as fluctuation of penetration depth, etc. ⋅Three detective signals were changed at the vertical hole and their wave forms varied before the hole position. ⋅The molten flow was observed by longitudinal cross section in weld test which Ni powder is packed in side holes. This work was performed under the management of ALERI (Applied Laser Engineering Research Institute) as a part of "the Leasing Basic Research Practical Use of Research Facility Centers" supported by NEDO (New Energy and Industrial Technology Development Organization).
Binarizing images are used usually for high speed processing in a vision system for an automatic recognition, inspection, or positioning of the micro-joints. In processing used a binarizing image, an automatic setting method of the threshold value is very important for a reliability improvement. The conventional binarizing methods are not corresponding to the change of the lighting. Especially, the threshold value is not select suitably for an image in which the brightness of the processing object exceeds a maximum value of quantization level. Therefore, in the conventional binarizing method, the size of the region divided by the binarizing processing has done a change by lighting environment at picturing. The brightness of the processing object exceeds a maximum value of quantization level in the pictured image of the printed circuit board, because the electric components mounted on a printed circuit board have various reflection rate for the light. Then, in this research, an automatic detection method which corresponds to a change of lighting environment that the brightness of the processing object exceeds a maximum value of quantization level is discussed. We propose a interval discriminate analysis thresholding method in which the threshold value is calculated based on the statistical analysis under the condition that the brightness of class 2 is transformed to the brightness at the boundary. In this proposal method, binarizing can be done at the same level relatively corresponding to a change of lighting environment. Furthermore, every valley part can be detect simultaneously for the gray histogram presenting many peak distribution.
To detect a specific region in an image is required for the vision system. In the detection of the micro-joints, detection method of the region where should detected in regions with the similar shape and consideration for the scattering of the size are very important. In this research, the shape expression method for the micro-joints in a computer and weighting value for each shape characteristic are discussed. It is shown that the evaluation method for the size of each shape characteristic based on the fuzzy set theory and the analytic hierarchy process method is effective. Furthermore, it is clarified that the synthetic evaluation used the weighting value calculated by the analytic hierarchy process method improve the ability of detection. At applying this automatic detection system to the detection of the QFP soldered joints on a printed circuit board, it is shown that the detection ratio is 100% and miss-detection is 0.
Flip chip joints on the epoxy base substrates were formed with Au bumps and several lead-free solders in order to evaluate the thermal fatigue behavior of those joints. The thermal cycle test and the observation of microstructures were performed with them. It was cleared that the joint with Sn or Sn-3.5Ag solder was almost changed to the Au-Sn intermetallics just after reflow soldering. On the other hand, no excess formation of intermetallics was found on the joints with other solders except Sn and Sn-3.5Ag. As the results of the thermal cycle test, it was found the indium base solders, such as In-48Sn, In-3Ag and pure In, showed the excellent thermal fatigue lifetimes. In these solders, the deformation of solder itself were observed after the thermal cycle test, and the main fracture mode was the solder cracks in the joints. That result indicates the indium base solders, which shows the good lifetime, are easily deformed against the thermal stress and released the stress by the deformation itself.
The purpose of this study was to make clear the mechanism of weld cracking in HAZ of long term used HP heat-resistant cast steel containing Nb, Mo and W when this steel was repaired. According to observation of fracture surface of weld cracking, a crack was regarded as a ductility-dip cracking. Moreover a crack propagated in microconstituents on dendrite boundaries. The amount, the structure and the precipitating site of microconstituents changed during aging at the temperature of 1323 K, which was the average temperature of materials during operating. On the other hand, the hot ductility at 773 K of these aged materials was evaluated using the Gleeble tester. It declined with the lapse of aging time. Comparing the change of microstructure with the change of hot ductility at 773 K, the decline of hot ductility was related to η phase (Nb3Ni2Si) and M23C6 precipitating like a network on dendrite boundaries for long aging. As a result, the decline of hot ductility of the base metal promoted weld crack in HAZ.
Microstructural analyses of the bonding interface in R-SUS304ULC/Ta/R-Ti-5Ta/Zr diffusion bonded joint were conducted in order to improve the embrittlement of the Ta/Zr interface. Diffusion bonding of R-SUS304ULC/Ta/R-Ti-5Ta/Zr was carried out at 1073-1373 K for 0-10 ks in vacuum. SEM and TEM observations revealed that the needle-like microstructure (transition zone) was formed at the Ta/R-Ti-5Ta and R-Ti-5Ta/Zr interface. Ta and α-Ti were identified in the transition zone at the Ta/R-Ti-5Ta interface, while the needle-like microstructure at the R-Ti-5Ta/Zr interface consisted of two kinds of α-(Zr, Ti) solid solution with different Ti compositions. The hardened area was located at the Ta/R-Ti-5Ta and R-Ti-5Ta/Zr interfaces, however, cracks didn't occur in the hardened zones. The growth of the transition zones could be expressed by the parabolic growth law during bonding operation.
Temper embrittlement, which occurs in the HAZ of 2 1/4Cr-1Mo steel subjected to SR treatment and subsequent reheating, was investigated by using the synthetic HAZ specimen, and it was compared with the embrittlement observed in the specimens tempered in the same temperature range without the SR treatment (direct tempering). With a suitable SR treatment (975 K for 5 hours) the synthetic HAZ specimen became the de-embrittled state. However, the subsequent reheating at 775 to 925 K produced in the specimens four different types of embrittlement. Those were the second, third, fourth and fifth types, which had already been recognized in the direct tempered specimens. The first type of embrittlement which arose in the direct tempering in the shortest time range did not appear after the SR treatment. The second type (the short time type), which occurred in a wide time-temperature range in the direct tempering, arose only in a narrow one after the SR treatment. The third and fourth types (the long time types) arose intensively as the case of direct tempering. The fifth type (the high temperature type) appeared also after the SR treatment. It will be concluded that the embrittlement in the short time range is suppressed to some extent by the SR treatment, but those arising in the long time range and the high temperature one arose after the SR treatment as well. It was found that "the step-cooling process" also could reveal the temper embrittlement of this steel. However, an essential advantage of this process over the isothermal tempering shown above was not recognized from the view point of promoting the embrittlement.
The low-pressure plasma spray coating process has been established in the field of gas turbines and is used for parts (turbine blades, duct segments, etc.) which are exposed to corrosive gases at high temperatures. Overlay coatings based on the MCrAlY alloy system (M is Ni, Co or Fe) are commonly employed as oxidation-and corrosion-resistant coatings. Mechanical properties such as fatigue lives, of CoCrAlY coated system were investigated at high-temperature as compared with the uncoated unidirectional solidified CM247LC and single crystal CMSX-2. Rotational bending fatigue properties of the CoCrAlY coated superalloy at high-temperature(1023 K) showed inferior performance in comparison with the uncoated results. It was because that the high stress due to Young's modulus difference was induced at the coating surface. It was also confirmed that the fatigue lives of CoCrAlY coating could be obtained by the rotational bending test.
A Ti-50.7 at % Ni shape memory alloy was welded by friction welding process at several upsetting pressures. The characteristics of individual phase which relates to shape memory phenomena and mechanical properties in a weld metal was investigated and discussed. Weld metal microstructures were identified using a transmission electron microscope (TEM). It turned out that as-welded microstructure consists mainly of B2 phase and is altered to B19' phase by a heat treatment. The NiTi2 phase was a prevailing precipitate. The density of dislocations in the B2 phase tends to increase with upsetting pressure. From these results, it can be concluded that the strength and shape memory effect of friction-welded joint in Ti-Ni alloy are comparative with those of the base metal.
This paper describes an alternative Si circuit chip joining technique and discusses factors affecting bond quality. In this technique, an Ar atom beam is used to sputter-clean surfaces to be bonded. After contaminants on the surfaces to be bonded are removed by Ar atomic beam irradiation, a thin LSI film is bonded to a substrate. The irradiation does not cause electrical damage to the device. Although the clean surfaces are quickly re-contaminated after the irradiation, the LSI can be bonded at low temperature and under light pressure. The joints have a few voids at the interface, but the mechanical and their thermal properties are good enough for electronic devices. This new joining technology offers the possibility of developing a defect rescue method for active device transfer.
In order to improve sliding wear characteristics at high temperature, the overlay weld metals for Co-based alloys with various amount of MoB particles were prepared using a plasma transferred arc welding process. Effects of amount of MoB particles on wear behaviors and friction coefficient of the overlay weld metals at high temperature were investigated using Ohgoshi wear tester and cylinder friction tester. The microstructures of overlay weld metals were consisted of Co-based matrix (βCo), lamellar structure of Cr23C6 and βCo, lamellar structure of M2B and βCo and primary crystal of CoMo2B2. The volume fraction of CoMo2B2 and hardness of overlay weld metals increased with the increase in the additional boron quantity. When the values subtracting the hardness of overlay weld metals from the hardness of S45C carbon steel were above HV300, the sliding wear resistance at high temperature was extremely improved. The friction coefficient of the overlay weld metals decreased with the increase of the test temperature. The reason is that the boride prevented the adhesion of S45C carbon steel to the overlay weld metals.
The fundamental requirements for torch construction have been clarified as in the following, which are to provide the specified curvature for a wire and are able to control its rotation at the same time for the sake of improving the accuracy to aim at target position in a weld joint. In order to provide a set curvature for the wire of 1.2 mm diameter, it is necessary to provide both radius of curvature of 90 mm or less and curve with the bend angle of 75° or larger for the torch. In case that the wrist (namely secondary axes) of a robot is twisted, it is difficult to restrict the rotation of the wire inside the torch only by selecting both simple curvature and bend angle for the curved torch. The rotation of wire tip can be restricted by providing a wire path with two curves having their centers of curvature in opposite positions each other. By using the wire reforming type torch such as the above, even in case that the bend direction of curvature of the wire supplied changes and/or a twisted wire is fed, the deflection of the wire tip from the datum of the torch can extensively be restricted and controlled to aim at the target position in joints. Furthermore, even if the wire conduit connected to the torch vibrates, the deflection of wire tip position is within about 0.1 mm and the stability of both welding current and voltage can be maintained until the end of life of a contact tube.