Hiizu Ochi

The formation of intermetallic compounds in aluminium alloy to copper friction-welded joints and their effect on joint efficiency

Pure aluminium to copper welded joints can be readily produced by friction welding or diffusion welding. Such joints are extensively used in the manufacture of heat exchangers and various types of components for electrical machinery to obtain lightweight products and reduce manufacturing costs. Because of joint softness, however, pure aluminium is not suitable for use in welded structures, although this combination of materials is expected to be usable in joints for welded structures through the softer pure aluminium being replaced by higher-strength aluminium alloys. Studies of aluminium alloy to copper welded joint combinations, however, have not yet been well documented. To obtain relevant fundamental data, this article describes an investigation of nine types of aluminium alloy to copper friction-welded joints to determine their weldability, weld interface, intermetallic compounds, and fracture modes. Previous studies have shown intermetallic compounds such as CuAl 2 and Cu 9 Al 4 to be formed in the pure aluminium to copper weld interface and the formation pattern of these intermetallic compounds to affect the joint strength. These results accordingly suggest that intermetallic compounds may also be formed in the weld interface of aluminium alloy to copper friction-welded joints. An effort was therefore made to investigate the intermetallic compounds formed in the weld interface of such joints, the fracture modes concerned, and their effect on joint strength.

Macrostructure and temperature distribution near the weld interface in friction welding of cast iron

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.

Friction Welding of AZ31 Magnesium Alloy

The authors have previously shown that the joint strength of friction-welded similar joints produced from ferrous materials, including friction-welded 6061 and 5056 aluminium alloy friction-welded joints, can be evaluated by the deformation heat input in the upset stage and upset loss. 2, 3 To validate this previously proposed evaluation method, i t is necessary to extend its application to other types of materials. It is also necessary to use the method to investigate not only similar joints but dissimilar joints as well. Studies of the latter joints are currently proceeding in parallel with investigations of similar joints. This article describes an investigation of AZ31 magnesium alloy similar joints. Magnesium alloys featuring a low specific gravity and good specific strength are extensively used in the manufacture of aircraft and industrial machinery components to exploit these characteristics. In terms of worldwide resources – ample raw material reserves being available in sea water and the earth’s crust – magnesium alloys are regarded as having viable applications in industry. Magnesium alloys, which also feature a number of other characteristics, such as good heat conduction, high coefficient of linear thermal expansion and ease of oxidation are regarded as difficult to join, although recent advances in joining technology have changed their status to joinable materials. In particular, previous joining difficulties can be easily overcome by friction welding as a solid-phase welding technique to provide easy joining. Friction welding of magnesium alloys was previously regarded as difficult, 7 whereas an AWS publication now describes them as joinable. This technological development may well be due to the effect of differences in welding conditions. Asahina et al have described the performance of friction-welded joints in argon gas to prevent oxidation and combustion, obtaining 90% joint efficiency. This article describes a study of AZ31 magnesium alloy friction-welded joints produced in air under a wide variety of friction welding conditions, investigating the possibility of the deformation heat input in the upset stage and upset loss being used to evaluate joint performance. The tensile strength properties of joints are also examined as joint performance parameters.

Ultrashort Open‐Tubular Capillary Column with Modified Silica‐Gel Thin Layer for Capillary Electrochromatography

Abstract 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.

Evaluation of joint strength of friction welded carbon steel by heat input

The friction welding process is used in various applications because of its many advantages, not least of which is its optimum suitability for joining dissimilar metals. However, in this process the heat source is the self-heat generation caused by friction and the heat generating surface directly becomes the friction weld interface; consequently the friction welding factors subtly influence the friction coefficients and the friction weld interface shows complex features. Thus fundamental issues yet remain, such as the difficulty in establishing appropriate welding conditions depending upon the test specimen materials and variation in the optimum welding conditions with different friction welding machines. Up till now, experimental results had been taken into account in deciding upon the parameters for the welding conditions in studies concerning conventional friction welding; however, it is difficult to adjust the welding conditions to achieve general characteristics solely by means of the above. Recently, Shinoda and others have energetically attempted to influence the joint strength using the heat input model. On the other hand, an attempt has been made by the authors to control the joint strength using the heat input measured during friction welding. Such a study is considered as a means of achieving the tasks described above.

Strength of 5083 aluminum alloy stud joints

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.

Strength of 2017 aluminium alloy stud joints by friction welding

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.

Statistical investigation on tensile strength of friction-welded joints of stainless steel to copper

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.

Numerical analysis of transient temperature characteristic of friction welding in 6061 aluminium alloy

The friction welding method, which enables welding to be executed with less energy and in a shorter time, has been used for the welding of various light metal machinery components, and many experimental research results on this technology have been reported. Meanwhile, as computers develop, more attempts have been made to analyse friction welding processes numerically, and proposals have been made for methods of estimating friction torque during friction welding. To estimate the heat input during friction welding and the transient temperature characteristic in the vicinity of the friction welded joints, the authors have proposed a simple method of combining the friction heat input model and the non-steady heat conduction analysis using the finite element method. This is a method which gives as parameters the base material’s material property, the friction pressure, and the rotation speed to estimate the temperature distribution in the vicinity of the friction welded joint. This method has so far been applied to the similar material friction welding of S25C and SUS304, and its validity has been confirmed. In this study, by applying this method to the friction welding of two similar materials of 6061 aluminium alloys, its validity will be examined by comparing the experimental results with the analytical results of the friction heat input and the temperature characteristic in the vicinity of the friction welded joint.

Statistical analysis of optimum friction welding conditions for 6061 aluminium alloy friction-welded joints

Abstract 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 conditions conform to a positively or negatively skewed distribution with heavy scatter while simultaneously having a small Weibull distribution shape parameter and large dispersion.