Ag is used as a useful alloying element in brazing filler metals. It is clear that the addition of Ag has a positive effect on the melting temperature, wettability, conductivity and mechanical property of the filler metals. For this reason, although Ag is very expensive, it is still widely used in many research and production. In this study, it was focused on obtaining both high strength and cost-effective brazing joints by using filler metals containing different levels of Ag. Melting-solidification temperatures, mechanical properties and microstructures of brazing joints obtained with filler metals containing different levels of Ag-Cu-Zn and Cd were investigated. In this study, the appropriate Ag content in brazing processes of pipes and caps used as copper-brass material pairing in cooling-heating devices in the air conditioning system was investigated in detail. When the typical microstructure of the joints was examined, it was observed that it mainly consisted of solid solutions and eutectic phases. The interfaces in the copper and brass regions were affected by both Ag content and melting temperatures. As a result of the burst test, the maximum stress value at which the brazed material pairs were damaged was found to be 345 MPa, and the damage was reported to occur in the copper pipe. In addition, it has been reported that the final product is damaged from the brazed zone when Ag-free solder wire is used. It was found that 5%Ag content provides sufficient performance in the final product due to the fact that the strength of the braze joint with low-Ag content is higher than the copper tube. The results also showed that the micro-hardness increased with the increase of Ag-addition, the hardness of the joint with the filler metal containing 5%Ag increased by 21%. The joint hardness obtained with filler metal containing 40% Ag showed an increase of up to 57%. This showed that the addition of Ag improves the strength, but its 5% Ag content provides sufficient performance in the brazing joint.

This paper investigates the quality characteristics of the welding geometry of the laser welding process for the ANSI 304 austenitic stainless steel, with the use of a pulsed Nd:YAG laser welding system. Laser welding of 2 mm thick ANSI 304 stainless steel is performed at three different levels of three factors, i. e., peak power, welding speed and pulse duration. In this study, a multi‐response optimization problem is developed to achieve weld bead geometry with full penetration as well as a narrow bead width and minimum crater. Grey relational analysis based on Taguchi orthogonal array is used to present an effective approach for the optimization of laser welding process parameters. Regression equations between the welding parameters and the bead dimensions for laser welded austenitic stainless steels are developed, which are used in predicting the penetration, width and crater. Finally, the equations are tested for values different from the levels of the parameters in the orthogonal array. It will be beneficial to engineers for continuous improvement in laser welded product quality.

Autogenous bead-on-plate laser welding was performed on 2 mm 304SS materials at different heat inputs. The influence of laser energy in low welding speeds on weld performance using a Nd:YAG laser was studied. The weld performance was characterized in terms of weld bead morphology, microstructure and mechanical properties. The result revealed that the crater increased with the increase of heat input, so there is a linear relationship between crater and heat input. The gradual increase of the heat input was not directly related to the penetration of the weld bead. At the highest heat input, weld beads considerably expanded and also the crater deepened, the hardness increased in these joints while tensile strength and ductility reduced. The best mechanical properties were obtained with high laser energy at intermediate heat input. These weldments exhibited better strength even better than base metal 304SS. The microhardness values were distributed homogeneously from the fusion zone to the base metal. Laser energy increased the ferrite network and brought finer ferrites. As a result, usable laser welding parameters in terms of good strength, as well as good ductility and weld bead morphology were defined for welding 304 SS with 2 mm thickness.

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The effects of two temper conditions (T4 and T6 heat treatments) upon the stress corrosion cracking (SCC) of AA6061 plates have been investigated in this work. AA6061 alloys were double-side-welded by the tungsten inert gas (TIG) welding method. SCC behavior of both the as-welded and as-received alloys was reported. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to determine the precipitate structure of the thermal-altered zones and the base metal (BM), and also the hardness variations were examined using microhardness testing (Vickers hardness). The small-size precipitate structures in the T6 tempered alloy and the coarser precipitate structures in the T4 tempered alloy were found by microstructural investigations. As a result, T4 temper heat treatment of this alloy considerably reduced its susceptibility to stress corrosion cracks due to relatively coarse and more separate precipitate morphology. In welded specimens, SCC failure occurred in the area between the heat-affected zone (HAZ) and the base metal. Stress corrosion resistance in the fusion zone was strong in both temper conditions. The aim of this work was to obtain the effects of heat treatment and welding on SCC behavior of the age-hardenable aluminum alloy. The authors conclude that a deep insight into the SCC resistance of AA6061 alloy indicates the precipitate particle distributions and they are the key point for AA6061 alloy joints in chloride solution.