Influence of Dynamic Stresses and Operating Environment on the Mechanical Properties of Copper-Based Braze Joints

With increasing use of the brazing process in industry, a vast knowledge about the mechanical behavior of brazed joints becomes fundamental in selecting the appropriate joining process. This study will present the mechanical behavior of brazed joints using a copper-based brazing filler alloy, BCu-1b. This choice was motivated by the wide application of copper-based fillers in the automotive industry. Tensile shear strength tests were conducted at room temperature, 100 °C and 200 °C using two different base materials (austenitic stainless steel 1.4301 and machining steel 1.0715) to investigate the influence of both the base material and the temperature. Brazed joints have often been claimed to deliver mechanical properties similar to that of the base material itself. In most of the cases this assumption refers to results of quasi-static mechanical tests, which often do not correspond to the real load. Indeed, brazing joints undergo typically dynamical mechanical stresses at different temperatures and frequently in corrosive environments. For this reason this study characterized the fatigue properties of the 1.4301/CU 101 brazed joints, too. Furthermore, brazed tensile samples were subjected to the cyclic corrosion test SAE J2334, which is used widely throughout the automotive industry. During this test the specimens were placed in an enclosed chamber and exposed to a changing climate that comprises dry/humid phases and immersions in salt water. Finally the corroded specimens were mechanically tested to verify the influence of this phenomenon on the strength of the brazed joints. This study provides outstanding information to evaluate the reliability of copper-based brazed joints under realistic service conditions.