Powder Metallurgy of Al-Al₂O₃ Composites (SAP) for Nuclear Applications

Abstract

An important application of the methods of powder metallurgy in the aluminum industry is the oxidation to a given degree of aluminum powder, followed by sintering of the oxidized powder obtained. Euratom has sponsored a large research effort on these materials in view of their application as canning materials and components for calandria tubes for nuclear reactors.

The paper gives the results of such work at the ISML Laboratory (Italy), which has been concerned with (1) the achievement of a completely structurally stable material during prolonged heating through an effective degassing treatment during the processing of the material, with the attainment of better weldability as a consequence; (2) the amelioration of the quality of the starting powder in order to obtain the maximum uniformity of the semifinished products; (3) the development of fabrication methods, which will yield straight tubing with narrow dimensional tolerances and finned tubes with straight or helical fins, and methods of control of these tubes; (4) the complete elimination of metallic impurities (e.g., iron) in order to achieve improved resistance to corrosion, better formability, more homogeneous behavior toward organic materials, and smaller neutron absorption (the special product obtained is called “Puroxal”—for pure oxidized aluminum); and (5) the structure of these materials has been more clearly interpreted, quantitative measurements of the grains and interspacings between the particles of the dispersed phase (Al₂O₃ and others, such as Al₄C₃ and AIN) are given, and a theory explaining the influence of temperature, rate of straining, etc., on the mechanical properties up to 500°C is proffered.