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Friction welding of C6191 aluminum bronze to SUS304L stainless steel was carried out to examine its weldability. Joint strength was evaluated by fatigue strength. The C6191 and the SUS304L at the weld interface were hardened, while the heat affected zone of the SUS304L was slightly softened. A reaction layer of 1–5 μm that consisted of component elements of the base metals was observed at the weld interface. The fatigue limit of the joint welded under the optimum welding condition was higher than those of the base metals because of the hardening of C6191 and SUS304L, and the fatigue limit of joints decreased as the friction time or the upset pressure varied. In particular, the fatigue strength of joints welded under the conditions varied the upset pressure which was lower than that of the C6191 base metal.

Stud joints of 5083 aluminum alloy were welded by arc stud welding and friction welding, and their joint strengths were examined. In the weld zone of the arc stud welded joint, no change occurred in the hardness distribution. In contrast, the weld zone of the friction-welded stud joint softened slightly on the plate side and hardened on the bar side. The tensile strengths of the arc stud welded joints with weld reinforcement and without weld reinforcement, and the friction-welded stud joints without burrs were 233, 231 and 180 MPa, respectively, and all joints fractured at the weld zone. In the bending test, all joints fractured near the weld zone at a bending angle of approximately 20°. In the fatigue test, the fatigue strengths of the arc stud welded joints were higher than those of the friction-welded stud joints, and the fatigue limits of the arc stud welded joints with weld reinforcement and without weld reinforcement, and the friction-welded stud joints without burrs were 43, 40 and 13 MPa, respectively.

Stud joints of 2017 aluminium alloy were friction welded and its joint strength was examined. A stair zone was formed at the weld interface. Although the hardness of the stair zone was almost the same as base metals, the heat-affected zone of the bar and the plate was softened. The tensile strength of joints tended to increase with a pressure and a friction time, and the highest tensile strength was 275 MPa (63.1% joint efficiency for the bar base metal). In the bending testing, joints were cracked in the weld zone at a bending angle of less than 5°. In the fatigue testing, joints fractured near the weld interface and the fatigue strength of joints increased as the tensile strength of joints was high.

Friction welding of SUS304 stainless steel to C1100 tough pitch copper was carried out and tensile strength of joints was examined. Also, a statistical analysis of the tensile strength data was investigated for judging a suitability of friction welding conditions on this joint. It was found that the SUS304 and the C1100 near the weld interface hardened and softened, respectively. There were fine-grained structures composed of much copper and a little of iron, chromium and nickel near the axial center at the weld interface. Tensile strength tended to increase with a friction time and with an upset pressure, and the maximum joint efficiency for the C1100 base metal was 101%. The shape parameter in Weibull distribution increased with an increase in mean value of tensile strength and with a decrease in dispersion of tensile strength. It seemed that the shape parameter is useful for judging the suitability of friction welding conditions.

t. Friction welding of FC250 common grade cast iron was carried out to examine the weldability and temperature distribution near the weld interface during welding. The joint strength of both solid and pipe joints was evaluated by tensile tests. The highest tensile strengths in the solid joints and pipe joints were 317 MPa (79% joint efficiency) and 381 MPa (95% joint efficiency), respectively. A fine-grained interfacial layer of FC250 formed near the axial center at the weld interface in the solid joints, whereas there was no fine-grained interfacial layer in the pipe joints. The welding material temperature at the axial center was higher than that at the periphery in the solid joint. There was little difference in the temperature distribution between the solid joints and pipe joints.

The relationship between joint strength and deformation heat input at the upset stage and the relationship between joint strength and upset bum-off length were examined on friction welded joints of 1050 pure aluminum to C1100 tough pitch copper. Joint quality was evaluated from the tensile strength and fatigue strength. It was found that both the deformation heat input at the upset stage and the upset burn-off length correlated well with joint strength. Additionally, when the deformation heat input at the upset stage or upset burn-off length exceeded a certain value, stable tensile strength was obtained. The mixing layer, intermetallic compounds of Al-Cu were interpolated into A1050, formed at the weld interface, and joints having a thick mixing layer fractured at the weld interface. Joint efficiencies of sound joints for the fatigue limit of the A1050 base metal were 88-100%. Judging from the fatigue limit, sound joints could be produced when either the deformation heat input at the upset stage or the upset burn-off length exceeded a certain value.

The Ono's rotary bending fatigue testing and the cantilever rotary bending fatigue testing were carried out on friction-welded 6061 aluminum alloy joints, and the relationship between the deformation heat input in the upset stage or the upset burn-off length and fatigue strength was examined. In the Ono's type testing, sound joints, which fractured in the heat affected zone in the tensile testing, fractured in the heat affected zone also and the fatigue limit of these joints is slightly lower than that of 6061 aluminum alloy base metal. This is because joints fractured in the softened area in both tensile testing and Ono's type testing using smoothed test specimens. While, in the cantilever type testing, the fatigue limit of sound joints was a little more than or a little less than that of 6061 aluminum alloy base metal. It seems that a weld condition and a structure at the weld interface affected fatigue strength in the cantilever type testing using notched test specimens. Judging from the fatigue limit obtained, sound joints can be produced when either the deformation heat input in the upset stage or the upset burn-off length exceeds a certain value.

Similar and dissimilar joints of 2017 and 6061 aluminum alloys were friction welded. Fatigue strength and fatigue life distribution of these joints were examined. The S-N curve showed that the fatigue strength of A2017/A2017 was almost the same as that of A2017 base metal, while that of A6061/A6061 was lower than that of A6061 base metal. The fatigue strength of A2017/A6061 was lower than that of A6061/A6061. The fatigue limit at 108 cycles of A2017 base metal, A2017/A2017, A6061 base metal, A6061/A6061 and A2017/A6061 were 120MPa, 120MPa, 70MPa, 60MPa and 55MPa, respectively. The shape parameter m and the location parameter γ in Weibull distribution function of the joints were lower than those of the base metals. These results suggest that the scatter in fatigue life distribution is larger and the smallest fatigue life is shorter for the present joints compared to the base metals.

Conferring lightweight and good corrosion resistance, aluminium alloy joints are extensively required in the manufacture of various types of electrical and mechanical components. Research data previously obtained by the authors1, 2 show the efficiency of friction-welded joints, regardless of whether produced from similar or dissimilar materials, to be fairly well scattered under identical sets of friction welding conditions and underline the need for statistical analysis of a large number of joints to determine the suitability of any specific set of friction welding conditions. That is to say, joints with a high mean joint efficiency that are friction-welded under optimum friction welding conditions conform to a normal distribution with low scatter during such statistical analysis while simultaneously showing a large Weibull distribution shape parameter and small dispersion. On the other hand, joints with a low mean joint efficiency that are friction-welded under unsuitable friction welding condi...

(2004). The formation of intermetallic compounds in aluminium alloy to copper friction-welded joints and their effect on joint efficiency. Welding International: Vol. 18, No. 7, pp. 516-523.

Aluminum alloys to S25C carbon steel were friction welded, and the friction weldability and intermetallic formations at the weld interface of joints were investigated. Joints of A1050, A5052, A6061 and A6063 to S25C showed good-weldability, and A5056/S25C joint was somewhat poor than former one. An intermetallic compound of Al13Fe4 was formed at the weld interface of A5056/S25C and A6061/S25C joints, and their intermetallic formations were tend to increase with friction pressure, friction time and rotation speed. The joint strength of these joints was high when thin instermetallic conpound layer was formed under high upset pressure. Somewhat poor-weldability of A5056/S25C joint compared with A6061/S25C joint seemed a cause of the intermetallic formation accelated by high content of magnesium in A5056. Joints of A2011, A2017, A2024 and A7075 to S25C showed poor-weldability. Brittle intermetallic compounds of CuAl2 and Al7Cu2Fe were formed at the weld interface of A2011/S25C joint containing a copper.

Molecular beam epitaxial growth of the widegap Zn1-xMgxO alloys on Si (111) substrates is reported. A series of single-phase wurtzite Zn1-xMgxO alloys with Mg-content up to x = 0.43 are successfully obtained. It is revealed by x-ray diffraction measurement that further increase from the Mg-content promotes inclusion of rocksalt Zn1-xMgxO alloys. Room-temperature cathodoluminescece spectra from these Zn1-xMgxO alloys show a blueshift of peak energy with increasing Mg-content.

A new preparation method has been developed that uses silica‐oligomer for the sub‐micron silica‐gel layer for the open‐tubular capillary column (OTC). The silica‐gel layer has a unique sub‐micron cell structure, which was observed by scanning electron microscope, and this structure contributes to increasing its total surface area. Using ultrashort (2 cm long) OTCs modified with docosyl methyl dichloro silane, separation of neutral compounds has been demonstrated. The column shows a good performance, such as theoretical plate number 71,000 plates/m. The column gives a relatively high capacity factor, such as 1.85 for fluorine.

In this paper, the effect of the upset timing on joint strength of the friction welded joints of 6061 aluminum alloy was discussed by using the evaluation factors of the deformation heat input in the upset stage and the upset burn-off length. The results showed the followings. When the upset pressure was applied before the braking, the deformation heat input in the upset stage and the upset burn-off length were so large more that sound weld joints could be obtained easily, than that of the synchronized timing at the same welding parameters. In the synchronized timing, when the upset pressure was large, the actual pressure could not attain to a set up pressure. Meanwhile, when the upset pressure was applied after the braking, the deformation heat input in the upset stage and upset burn-off length were so small that sound weld joints could not obtained. Therefore, it was made clear by using effect of the upset timing in joint performance was much related with the deformation heat input and upset burn-off length. And the sound welded joints were obtained with 200 J/s or more deformation heat input and 2.5 mm or more upset burn-off length.

Friction welding of aluminum alloys to copper was carried out in order to examine the weldability with particular reference to the effect of the intermetallic formation at the weld interface. The maximum joint efficiencies of A1050, 5000 and 6000 series alloys to copper were more than 80 %, while those of 2000 series and A7075 alloys joints were less than 50 % and scattered widely. For joints of A2024 and 5000 series alloys which contain rather high magnesium content, intermetallic compounds of Al-Cu-Mg system were formed at the weld interface in addition to that of Al-Cu system. In the other joints, only intermetallic compounds of Al-Cu system were formed. A mixing layer, in which pieces of copper and intermetallic compounds were incorporated into aluminum alloy, was formed near the weld interface. The mixing was very intense, in the joints with low efficiency, namely joints of A2011, A2024 and A7075 to copper, and these joints were fractured in this mixing layer and at the weld interface. On the other hand, the joints with high efficiency, namely joints of A5052 and A6061 to copper, had thin and even mixing layer. The mixing layers observed in the joints of A1050, A2017, A5056 and A6063 to copper were thinner than those of the other joints.

It has been difficult to obtain single crystalline ZnO films on Si substrates due to the oxidation of Si surface during initial ZnO growth. In this letter, we report the growth of single crystalline ZnO films on Si (111) substrates using a buffer layer of CaF2. The films were grown by radical source molecular beam epitaxy, and revealed by x-ray diffraction to be in the c-axis orientation without in-plane rotational domains. An ultraviolet photoluminescence corresponding to the bandgap energy was dominant for the films even at room temperature. It is indicated by the results that the use of CaF2 buffer layer is promising for the growth of high-quality ZnO (0001) films on Si (111) substrates.

Friction welding of 6061 aluminum alloy was carried out in order to examine the relationship among deformation heat input at the upset stage, upset burn-off length and joint performance. The joint performance was evaluated by tensile testing and fatigue testing. Stabilized tensile strength was obtained when the deformation heat input at the upset stage and the upset burn-off length exceeded 200J/s and 4mm, respectively. Weld condition at the weld interface and the width of softened area affected fatigue strength more than tensile strength. That is, when the weld condition at the weld interface is good and the softened area is wide, fatigue strength increases because the stress disperses in the softened area. On the other hand, when the weld condition at the weld interface is good and the softened area is narrow, and when the weld condition at the weld interface is somewhat poor in spite of the wide softened area, fatigue strength decreases because the stress concentrates at the weld interface. The fatigue limit obtained by the fatigue testing reveals that, when the deformation heat input at the upset stage and the upset burn-off length exceed a certain value, sound joints can be produced.

Friction welding of S15CK carbon steel was carried out in order to examine the relationship between heat input for welding and joint strength. The joint strength is evaluated from tensile strength. The heat input is a heat source for welding solid materials and was classified into 6 inputs: friction heat input, deformation heat input and total heat input in the friction stage and upset stage.The most important heat input for evaluating the joint strength among these heat inputs was experimentally investigated through the tensile strength of joints welded under various welding conditions.As a result, it was made clear that the deformation heat input in the upset stage is much strongly related with the joint strength, and sound weld joints can be obtained deformation heat inputs more than about 100J/s. Moreover, it was recognized that the joint strength is possible to evaluate by the upset loss, therefore, sound welded joints can be obtained with about 1.2 mm upset burn-off length or more also.

Carbon steel was friction welded and torsion fatigue tests were conducted on weld joints having an upset burr in order to reveal the effect of an upset burr on fatigue strength. It was found that the fatigue strength of joints having a constant toe radius decreased with a decrease in hardness ratio (hardness of toe/hardness of base material). Softened joints (hardness ratio≤1) and hardened joints (hardness ratio>1) fractured at the toe of the upset burr and in the base material, respectively. On the other hand, the fatigue strength of joints having constant hardness ratio increased with toe radius. Using correlation analysis, a reasonable multiple regression equation was obtained between torsional fatigue strength and the fatigue factors, that is, the hardness ratio and toe radius of the upset burr. Thus, using this regression equation, the torsional fatigue strength of friction welded joints having an upset burr could be estimated.

The tensile strength characteristics of friction welded joints of several aluminum alloys (A1050, A2017, A6061) to stainless steel (SUS304) were investigated by statistical analysis such as normal distribution and Weibull distribution. The results are as follows. The joint efficiencies of joints obtained under an optimum welding condition followed by a good joint showed near normal distribution with higher mean value and small dispertion, and furthermore showed a Weibull distribution with large shape parameter and small coefficient of variance. On the other hand, the joint efficiencies of joints obtained under the unsuitable welding condition followed by a poor joint showed a plus or minus distortional distribution with large dispertion and showed a Weibull distribution with small shape parameter and large coefficient of variance. Thus, the optimum welding condition could be obtained in the case of A1050 to SUS304 and A6061 to SUS304, but couldn't be obtained in the case of A2017 to SUS304 in this experiment.

Friction welding of 6061 aluminum alloy similar material was carried out in order to examine a relationship between heat input and joint performance. The joint performance is evaluated by tensile test. The heat input is a heat source for welding solid materials and is classified into six inputs, that is, friction heat input and deformation heat input during friction stage, upset stage and total stage respectively. The most important heat input for evaluating the joint performance among these heat inputs was experimentally investigated through the tensile strength of joints welded with many welding conditions because the friction welding mechanism is so complexed. As the results, the deformation heat input during upset stage was much related with the joint performance, and sound welded joints were obtained with 200 J/s or more deformation heat input. Moreover, it was recognized that the deformation heat input during upset stage was in proportion to the upset loss, therefore, sound welded joints were obtained with 3 mm or over upset loss also.

Friction welding of various aluminum alloy pipes to SUS304 stainless steel pipe was carried out making clear weldability at dissimilar material pipe. A1050/SUS304, A5052/SUS304, A5056/SUS304, A6061/SUS304 and A6063/SUS304 joints showed good weldability and the maximum joint efficiencies of these joints in tensile test were about 91%, 71%, 60%, 79% and 97%, respectively. In these cases, the formation of Al13Fe4 intermetallic compound was induced by the interdiffusion through the weld interface. On the other hand, other joints had poor weldability. In the cases of A2011/SUS304, A2017/SUS304 and A2024/SUS304 joints, CuAl2 and Al7Cu2Fe were observed on the friction surface, and the maximum joint efficiencies of these joints were about 26%, 39% and 32%, respectively. For the case of A7075/SUS304 joint, Al23CuFe4 was observed on the friction surface, and the maximum joint efficiency was about 37%.

Friction welding of 6061 aluminum alloy to steels was conducted, the effects of welding conditions and various heat treatments of the welded joint on the joint strength were examined. Under the same welding conditions, the tensile strength of A6061/steeI joints were much alike for all the steels used. Tensile strength was seen to increase when the upset pressure was raised. In the case of joints welded at upset pressure not less than 80MPa, tensile fracture occurred in thermal softened A6061 area and the tensile fracture surface approached closer to the weld interface according to increases in the upset pressure, because softened A6061 was exhausted with burr under the action of upset pressure. It was concluded that joint strength depends on the width of the softened A6061 area. The whole A6061 area of T62 heat treated joint hardened to the same extent as the received material of A6061-T6, and tensile strength of this joint was high compared with that of the weld joint.

Molecular beam epitaxial growth of a wurtzite ZnS/ZnO heterostructure on a-plane sapphire substrate is reported. X-ray diffraction and cathodoluminescence measurements revealed the formation of a ZnOS alloy layer at the heterointerface. Bandgap bowing parameter for the ZnO-ZnS binary system was roughly estimated to be ∼4.1 eV using an intense visible emission from the interface layer. Such a large bowing is due to the difference in electronegativity between S and O atoms. It is also found that the visible emission peak was pronounced by an ex-situ thermal annealing due to the progress of alloying.

Friction welding of 2017 and 6061 aluminum alloys in as-received, solution heat treated and aged states was conducted under the optimum welding condition for as-received specimens. As friction-welded, tensile strength ofjoints was approximately equal to the mother 6061 alloy for every temper states. When the joints were post-heat-treated, brittle fracture occurred at the welding interface and/or pan-cake-like recrystallized boundaries in the vicinity of the interface. A mechanism of friction welding and an origin of embrittlement were discussed on the basis of the effects of heat treatments, on the hardness distribution changes of the joints and also on the fractographical features of tensile specimens.

Destructive test of the joints was carried out for examining the impact and fatigue strength. The softened area of A6061 side of the joints welded under a higher upset pressure is narrower compared with that welded under a lower upset pressure, because the softened area of A6061 side was expelled as the upset burr by the action of upset pressure. The dynamic strength of the joints depends on the width of the softened area of A6061 side. In the case of smoothed impact specimen, the impact absorbed energy of the joints increases with increase in upset pressure, while it decreases with the upset pressure over 240 MPa. On the other hand, no smoothed specimens of A6061 base material fracture. In the case of notched specimen, the impact absorbed energy of the joints welded under the upset pressures over 160 MPa remains to be almost equal to the maximum value, and the maximum joint efficiency is about 15%. The impact fracture occurres both in the mixed area of the weld interface and in the softened A6061 area. The fatigue strength at a given endurance (number of cycles to failure 107) of A6061 base material and the joints welded under 120 MPa and 240 MPa upset pressure are 121 MPa, 112 MPa and 122 MPa, respectively. The fatigue fracture of the joints occurres in the softened A6061 area or in the mixed area of the weld interface and the softened A6061 area depending on the welding conditions.

Friction welding of a 6061 aluminum alloy to a S45C carbon steel was carried out using the insert metal of a 1050 aluminum. Optimum thickness of the insert metal, friction pressure, forge pressure, friction time and rotational speed of welding conditions were determined as 4mm, 90MPa, 300MPa, 1.2s and 2250rpm, respectively. When the insert metal turned into a thin (20-30μm) and homogeneous layer at the weld interface, the maximum joint efficiency of tensile strength was obtained and was about 95%. Successful welds were obtained by taking each optimum welding condition even if the thickness of the insert metal was varied from 2 to 6mm.

The optimum welding condition for brake type friction welding of titanium and SUS304 stainless steel was investigated using a response surface method. The optimum friction pressure, forging pressure, friction time and rotating speed of welding were determined as 91MPa, 195MPa, 0.8s and 1842rpm, respectively. The joint welded in CO2 gas had higher tensile strength than that welded in air. The transformation of α-Ti into β-Ti and γ-Fe(Cr) into α-Fe(Cr), and the formation of intermetallic compound (Fe(Ni)•Ti) were induced by the interdiffusion along the welding interface. The joint strength depends on the width of β-Ti and Fe(Ni)•Ti layer.

(CdZn)S alloy semiconductor thin films were deposited by sputtering for the application to solar cells and the deposition conditions were investigated to obtain n-type low-resistivity films with high visible light transmission. (CdZn)S thin films with a chemical composition close to stoichiometry were obtained by using a composite sintered target of sulphur-rich CdS and ZnS. When a CdS film was deposited on a glass substrate under the optimum condition, the film was a polycrystalline film with highly oriented grains whose diameter was 200 nm. The composition ratio of (CdZn)S could easily be controlled and was close to the molar ratio of Cd to Zn in the target. In2S3 and CdCl2 were used as the n-dopant. CdCl2 provided an excellent doping property without degradation of the film quality although In2S3 tended to segregate in the form of CdIn2S4. When a CdCl2-doped Cd0.8Zn0.2S film was deposited under the condition optimum for CdS deposition, the bandgap was 2.65 eV and the resistivity was 10 Ωcm. Therefore, this film can be promising as the window material for a heterojunction solar cell.