Assessing coupled mechanical behavior and environmental degradation at submicron scales
Mechanical and electromechanical properties, deformation and fracture mechanisms, and environmental resistance of materials at submicron scales have been investigated through the combination of nanomechanical testing, high resolution microscopy, diffraction, and electrochemical testing. Nanomechanical techniques were used to isolate environmental, orientation, and size effects. Material evaluation focuses on metals, both model and engineering alloys, in bulk and thin-film form as well as oxide-substrate systems. Yield behavior of Ni 200, a model material, depends on sampled volume size, orientation, and surface preparation. Exposure to high-pressure hydrogen gas is also found to impact incipient plasticity and mechanical properties of commercially pure Ni 201. Nanomechanical testing of oxide-substrate systems can be used to study coupling of environment and size effects. Investigation of films grown on 304L stainless steel and commercially pure grade II Ti via nanosecond pulsed laser irradiation has enabled isolation of film fracture behavior and the effect of processing on mechanical and electromechanical properties. Additionally, laser processing causes substrate composition gradients that limit environmental stability. Combining techniques provides a unique approach for understanding and improving materials reliability in harsh environments.
Bahr, Purdue University.
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