Accession Number : ADA114809

Title :   Strengthening and Strength Uniformity of Structural Ceramics.

Descriptive Note : Annual rept. 1 Feb 81-31 Jan 82,


Personal Author(s) : Lange,F F

PDF Url : ADA114809

Report Date : Mar 1982

Pagination or Media Count : 69

Abstract : The first year effort of this program has produced a major advance in uncovering the processing steps that result in strength degrading flaws in sintered ceramics. This advance was initiated when a dye-penetrant was used to examine sintered materials (namely, a series of tough A1203/Zr02 composites). As detailed in Appendix 1, successful attempts were made to eliminate the low density volume elements by HIPing (Hot-Isostatic Pressing), and strength increased as expected. But when the fracture origins were examined, only low density porous regions were observed in the HIPed materials. The hypothesis that agglomerates in a powder compact lead to crack-like voids directed the second and major part of this year's effort detailed in Appendix 2. It was reasoned that the major differences between agglomerates and between agglomerates and their surrounding powder matrix were green density differentials. The third piece of work demonstrated how improper milling conditions can lead to strength degrading agglomerates in two-phase composite ceramics as detailed in Appendix 3. Large, hard Zr02 agglomerates in the Zr02 powder were not broken apart when they were milled together with the A1203 powder.

Descriptors :   *Ceramic materials, *Sintering, *Strength(Mechanics), Fractography, Fracture(Mechanics), Agglomerates, Mathematical models, Equations, Differentials(Mechanical), Reaction kinetics, Isostatic pressing, Cracks, Voids, Density, Stress strain relations, Aluminum, Oxygen, Zirconium, Structural analysis, Microstructure

Subject Categories : Ceramics, Refractories and Glass
      Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE