Micromechanical studies on effective moduli and microstructural sizeeffect forγ-TiAl-based alloys based on micropolar theory

To investigate the size effect of effective elastic properties for a nearly lamellar γ- TiAl based alloy , amicromechanical method was developed based on the micropolar theory. The emphasis was placed on proposing ananalytical-micromechanical model. In cont rast to the classical micromechanics theory , the model was const ructed byusing the orientational average over all PST ( Polysynthetically twinned crystal ) grain orientations and extendingMori- Tanakaps method to micropolar mediums. The computed result s show that the size dependence is morepronounced when the PST particleps size a approaches the mat rix characteristic length lm , and with decreasing thediameter of PST particles , the effective elastic moduli of γ- TiAl based alloy increase. The classical prediction ofeffective elastic properties for Cauchy mediums is recovered when the PST particleps diameter tends to infinitycompared to the characteristic length of the micropolar mat rix.