[Development of Fractal Fractography in Fracture-behavior Investigations of a Zn-al Alloy]

Analysis of self-similarity of a rupture surface requires sampling This implies precautions which, if neglected, can lead to false conclusions concerning the fractal character of the analyzed object. The fractographic procedure derived from the Minkowski-Bouligand method reveals self-similarity on more than two decades of observation scales of all the rupture profiles analyzed. The fractal hypothesis is adequate. The fractal dimension D(f) is a fractographic indicator which reveals the effect of the microstructure on the rupture mechanism. The mechanical conditions under which the crack progresses influence the D(f). The question of the relation between D(f) and tenacity is raised again

The Influence of High Sintering Temperatures On the Mechanical-properties of Hydroxylapatite

The kinetics of the thermal decomposition of stoichiometric hydroxylapatite (HA) has been studied up to 1500 degrees C for the purpose of determining the maximum admissible combinations of temperature and time for sintering HA. The influence of the sintering temperature on shrinkage, density and grain growth is then investigated in the temperature range from 1000 to 1450 degrees C. Nearly theoretical density was achieved above 1300 degrees C. A maximum fracture toughness is obtained for the samples sintered at 1300 degrees C whereas hardness increases up to a sintering temperature of 1400 degrees C. These results are discussed in terms of the roles of porosity and grain size

Zn-al Matrix Composites - Investigation of the Thermal-expansion, Creep Resistance and Fracture-toughness

Composites of Zn-A1 alloys (ZA8 and ZA27) reinforced by fibres of alumina, carbon or steel have been prepared by squeeze casting. Microstructural observations reveal the segregation of the zinc-rich phase around the fibres. The composites exhibit a greatly reduced creep rate in comparison with the matrix alloys. The thermal expansion coefficient is also significantly decreased. The impact toughness has been studied by Charpy tests