Properties and applications of dispersion-strengthened metals

Abstract

In summary, therefore, dispersion-strengthening has significantly increased the useful temperature range of such metals as aluminum, copper, nickel, and tungsten, and other experimental alloys are currently being developed. Fig. 12 illustrates the strengthening achieved with various classes of alloys as a function of temperature. Although at lower temperatures precipitation-hardened alloys will be stronger than the dispersion-strengthened alloys, the converse is true at elevated temperatures, particularly for extended periods of loading. Also, the physical and chemical properties of dispersion-strengthened alloys are normally similar to those of the matrix metals. Thus, design engineers may be able to select the matrix for other properties than its strength and incorporate a dispersion in it to obtain the required strength. However, deformation of a dispersion-strengthened matrix generally requires higher pressure and temperature and less severe reduction because of the lower ductility and higher strength resulting from the presence of the dispersoid. Also, the change in mechanical properties caused by deformation and heat treatments is usually reduced by the presence of a dispersoid. Finally, although superior to other types of alloys at elevated temperatures, dispersion-strengthened alloys are currently limited by low strengths at low temperatures, reduced welded and brazed joint efficiencies at high temperatures, and lack of guaranteed minimum mechanical properties.