Abstract
The investigation of phase transformations in metastable ceramic systems such as zirconia often requires local phase analysis within the areas of interest. Electron backscatter diffraction is a suitable method. The effect of the combination with focused ion beam sample preparation was determined in this work. In addition metal matrix compositemetal matrix composite honeycombs and foams as well as beads were investigated. The foams and honeycombs were composed of austenitic steel exhibiting TRansformation Induced Plasticity (TRIP) and magnesia partially stabilized zirconia. Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray Computed Tomography Device (XCT). By using a recently developed reconstruction algorithm, local deformation was calculated and regions of interest were defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction. The results show a strong correlation between local deformation and phase transformation.
Highlights
Metal matrix composites (MMCs) have been in the focus of research and development for many years
Damage was the dominating effect for angles of 72° while phase transformations occurred during Focused Ion Beam (FIB)-preparation with 30 kV, 30 nA and 5° incidence angle
Using 5 kV, 4.8 nA and 5° incidence angle no phase transformations and no damage were observed. These conditions are suited for the FIB preparation of metastable zirconia
Summary
Metal matrix composites (MMCs) have been in the focus of research and development for many years. The combination of the deformation-induced phase transformation of the steel matrix with the stress-assisted martensitic phase transformation of the Mg-PSZ produces composite materials with high damage tolerance [6]. This opens up a wide field of application for high-strength materials that possess the capability of absorbing mechanical energy during, for example, crash loading. MMC foams [11] and honeycombs [12] were examined The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. Composite beads with graded layer structures (prepared with the alginate gelation technology) were examined and valued with X-ray computed tomography [13]
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