Transient Liquid Phase Bonding of High Strength Aluminum Alloy

The focus of the research and experiments in this thesis is Transient Liquid Phase (TLP) Bonding of high strength aluminum alloy using pure zinc as an interlayer material. The primary goal of this research was to determine if high strength TLP bonding of aluminum alloy 7075, the most common alloy used in aerospace structures, could be achieved, and if so, without causing significant loss of strength to the aluminum alloy. In order to do this, many experiments were conducted to determine the appropriate bonding parameters. Preliminary experiments involving various heat treatments of aluminum 7075 samples were conducted to establish an acceptable range of bonding temperatures. Before and after heat treatment, each sample was tested for ultrasonic pulse velocities and hardness values. These values were compared and an initial bonding temperature was determined. Several sets of bonding experiments were performed applying variations of surface treatment, bonding temperature, bonding duration, and interlayer material. After bonding, each sample was subjected to multiple types of analysis to assess the quality of the bond. Samples were visually inspected, scanned using a high definition Scanning Acoustic Microscope (SAM), tested for shear strength using a Mechanical Testing System (MTS), and inspected with an optical metallographic microscope. Results of each set of bonds determined the variations applied to the following set. After many experimental bonds were tested, conclusions were drawn to establish optimal bonding temperature and duration. Shear strength results were analyzed considering structural aspects of the test specimens and limitations of the MTS. Future research and experiments that could be done to further understanding of this subject matter was then identified.