Master of Science in Mechanical Engineering (MSME)
In this study, Ni/Al multilayer foils were fabricated by a cold rolling method. A two-stage reaction process was observed in the reaction-ignition experiment. The phase formation process in the cold rolled foils was studied. The first reaction stage with a slow reaction velocity was the lateral growth of Al3Ni phase at isolated nucleation sites and the subsequent coalescence into a continuous layer. The second reaction stage with a fast reaction velocity was the growth of the Al3Ni layers in the direction normal to the Ni/Al interface until all Al was consumed. Afterwards, Al3Ni reacted with the remaining Ni to form the final reaction product, AlNi. The reaction velocities of the first reaction stage for the cold rolled foils were around 7 mm/s. Ti/Al multilayer foils were also fabricated by cold rolling to test whether this method can be extended to fabricate other metal/aluminum multilayer systems. The entire reaction process for the cold rolled Ti/Al multilayer foils was identified, which was similar to the cold rolled Ni/Al multilayer foils. Reactive multilayer foils can be used as local heat sources to melt solder or braze layers and thus bond different components. Silicon wafers were bonded using reactive Ni/Al multilayer foils. A numerical model was developed to predict the temperature evolution during the bonding process. The simulation result showed both localized heating and rapid cooling during reactive foils joining process. Based on our experimental observation, the bonding strength of the reactive bond was estimated to be larger than the failure strength of bulk silicon. Moreover, leakage test in isopropanol alcohol (IPA) showed that reactive foils bonds possessed good hermeticity for liquid.
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Qiu, Xiaotun, "Reactive multilayer foils and their applications in joining" (2007). LSU Master's Theses. 2091.