50 µm

1. Transient Liquid Phase (TLP) Bonding of 321 Stainless SteelMatthew N. Cavalli, University of North Dakota Main Campus, DMR 0907616 Stainless steel alloys are widely used in industrial processes for both their high temperature properties and their chemical resistance. Alloy 321 was selected as a representative iron-based high temperature alloy for the current work. It exhibits good strength and resistance to sensitization up to about 900C. Diffusion bonding of 321SS with Au-12Ge foil showed a dependence of the joint strength on bonding temperature, bonding time, the bonding atmosphere (argon versus vacuum), and the cooling rate after bonding. The best strength results were obtained after bonding at 1050C for 20 hours in an argon atmosphere and quenching the joint in water. a b 50 µm 50 µm The figure above shows 321 Stainless Steel diffusion bonded at 1050C for 20 hours in an argon atmosphere using a foil of Au-12Ge and a) cooled in air or b) water quenched. Void formation and the distribution of second phase particles are significantly impacted by the cooling rate. The tensile strength of b) was approximately 3X higher.

2. Engineering OutreachMatthew N. Cavalli, University of North Dakota Main Campus, DMR 0907616 Due to a lack of interest by high school students in attending the ‘Experience Engineering’ summer program this year, the camp had to be cancelled (only 2 students had registered by mid-June). Instead, the PI and his graduate students spent a significant amount of time helping organize events for the Young Scientists and Engineers academy for grades 1-8. Each group of about 30 students (grades 1-4 and grades 5-8) spends four half-days on various science and engineering topics. Activities this year included air pressure, friction, aerodynamics, global positioning, chemical reactions, electronics and motors, and medicine. As part of the Access for American Indian Students into Engineering Education program in December 2011, the PI led a discussion with Native American high school students about what engineers do and how their work affects our lives. An student volunteer helps participants in the Young Scientists and Engineers Academy assemble robots that ‘walk’ with the help of mass asymmetry on a rotating motor.