Fibering Of Oxides In A Refractory Metal Matrices

The report is intended to update DMIC Report 241, which describes research on fiber-reinforced metal-matrix composites for the period 1964-1966. A two page summary outlines the current state-of-the-art of these composites, and is followed by a discussion of 1967 research on the composites, arranged according to matrix- and fiber-materials. The bulk of the report consists of summaries of 1967 research programs, arranged by programs. (Author).

The purpose of Oxide-Based Fiber-Reinforced Ceramic-Matrix Composites is to provide comprehensive information on the most recent successful findings. The book consists of six chapters which characterize the current state of the art concerning oxide-based fiber-reinforced composites. Chapter one provides an introduction, examples of application areas and background information. Chapter two deals with the primary material properties for the areas of application and lists the possible constituent parts of the composites, depending on particular demands. Chapter three explains both the past and present fabrication methods which can affect the performance of the composites. Chapter four defines the interphase-related phenomena and describes the mechanical characteristics of the oxide-based fiber-reinforced composite, produced with different interphases. Chapter five deals with the fabrication route, functionality and mechanical characterization of the porous-matrix composites. The last chapter summarizes the present achievements and identifies requirements for reaching the goal, thereby providing a promising course for future research.

Refractory oxide particles of urania (UO2) and zirconia (ZrO2) were added to a tungsten matrix and elongated into fibers by hot extrusion. Extrusion temperatures ranged from 3200 degrees to 4000 degrees F (1760 degrees to 2200 degrees C). The geometry of the oxide fibers appeared to be closest to that of an ellipsoid with the major axis alined in the extrusion direction. Oxide fibering was measured by an average length-to-width ratio of the fibers sectioned parallel to the major axis. the extent of oxide deformation was estimated in terms of strain components. Oxide-matrix deformation characteristics were related to the extrusion parameters by comparing the estimated oxide strain components to those of the composite. In terms of fibering, the greatest oxide elongation average length to width ratio = 200, was obtained in tungsten-UO2 composites extruded at 3600 degrees F (1980 degrees C) with a composite reduction of 18 to 1. values of average length to width ratio for tungsten-UO2 composites extruded at 3200 degrees and 4000 degrees F (1760 and 2200 degrees C) were nearly equal (average length to width ration =100) even though the composite reductions were 12 to 1 and 18 to 1, respectively. For a tungsten-ZrO2 composite extruded at 4000 degrees F (2200 degrees C), average length to width ratio =160. These length-to-width ratio values have no direct relation to the length-to-diameter ratio commonly used to describe fibered composites containing cylindrical fibers.