Materials Testing and Characterization Laboratory

This program is focused on the investigation of processing-structure-property relationships in advanced materials. Materials of interest include, but are not limited to, high temperature materials (Titanium Aluminides and their composites), superplastic materials (Titanium and Aluminum), superconducting materials, high-strength conductors and Polymeric Matrix composites. The program is divided into three areas of specialization: Processing and Testing, Materials Characterization and Micromechanical Modeling. The laboratory is directed by Professors Garmestani and Kalu.

Material processing may be used to produce a desired shape or to enhance mechanical properties. Here, we employ deformation processing, such as rolling, forging or wire drawing, to improve the mechanical properties of materials. The type of processing used depends on the properties and microstructure of the material. Mechanical testing is performed in order to study the tensile/compressive properties, fatigue behavior, and superplastic phenomena in materials. Other transient type testing includes load relaxation experiments, strain rate change tests, and creep tests. The facilities available for the study include two MTS systems with high temperature capability.

To improve the mechanical properties of materials, it is necessary to identify and measure vital metallurgical parameters at several stages of processing. The parameters include grain size and morphology, residual stress, microplasticity and (sub)grain boundary misorientation. Our conventional microstructural characterization facility consists of optical microscopes, an X-ray diffractometer, a scanning electron microscope (SEM), and an environmental scanning electron microscope (ESEM). Novel techniques have been developed for the study of local texture (microtexture) and residual stress in materials. This include Electron Backscattered Pattern (EBSP), Orientation Imaging Microscopy (OIM) and Microscopic Strain Field Analysis (MSFA) techniques. The Particle Imaging Velocimetry (PIV) technique developed by our Department's Fluid Mechanics group is currently being explored for use in material characterization as Microscopic Strain Field Analysis (MSFA). This technique can provide local displacement (strain) contours in different phases of a heterogeneous material.

The modeling efforts provide an opportunity to correlate the material properties with microstructure. The metallurgical parameters used for parametrization may vary from one material to another. Phenomenological, micromechanical and statistical modeling approaches are currently used. The mechanical modeling effort is being used to explain creep, superplasticity and fatigue of high temperature advanced materials including composites. Our modeling efforts, while phenomenological, are based on physical parameters and relate the micromechanics to mechanical properties such as stress, strain rate and hardness.