ABSTRACT
This study compares thermal aging effects in Inconel 690 (IN690) produced by forging and powder metallurgy with hot isostatic pressing (PM-HIP). Isothermal aging is carried out over 400-800°C for up to 1000 h and then metallography and nanoindentation are utilized to relate grain microstructure with hardness and yield strength. The PM-HIP IN690 maintains a constant grain size through all aging conditions, while the forged IN690 exhibits limited grain growth at the highest aging temperature and longest aging time. The PM-HIP IN690 exhibits comparable mechanical integrity as the forged material throughout aging: hardness and yield strength are unchanged with 100 h aging, but increase after 1000 h aging at all temperatures. In both the PM-HIP and forged IN690, the Hall-Petch relationship for Ni-based super-alloys predicts yield strength for 0-100 h aged specimens, but underestimates yield strength in the 1000 h aged specimens because of thermally induced precipitation.
ABSTRACT
A multidisciplinary science experiment was performed in K-12 classrooms focusing on the interconnection between technology with geology and chemistry. The engagement and passion for science of over eight hundred students across twenty-one classrooms, utilizing a combination of hands-on activities using relationships between Earth and space rock studies, followed by a remote access session wherein students remotely employed the use of a scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) to validate their findings was investigated. Participants represent predominantly low-income minority communities, with little exposure to the themes and equipment used, despite being freely available resources. Students indicated greatly increased interest in scientific practices and careers, as well as a better grasp of the content as a result of the lab and remote access coupling format.
