The effects of laser treatment on the mechanical response of polycrystalline titanium (99.99%) have been investigated using the laser gas nitriding technique. Samples were subjected to irradiation by a 532 nm pulsed Nd:YAG laser for 100–400 shots. Laser pulses of energy 370 mJ with 10 Hz repetition rate were used to irradiate the surface of specimens and to activate the reaction between the irradiated surface and nitrogen. The effects of multiple laser pulses on the microstructure, yield stress (YS), ultimate tensile stress (UTS) and microhardness of the specimens were examined. Characterization of both the unirradiated and the irradiated specimens was carried out using a scanning electron microscope, an x-ray diffractometer and an energy dispersive x-ray spectrometer. The results show that irradiation of the specimens resulted in the growth of grains in the beginning and then their segregation as the number of laser shots was increased. An incorporation of nitrogen ions into the surface is also observed. The microhardness was found to increase with increasing laser shots, whereas changes in YS and UTS with laser shots were found to be anomalous.

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The temperature dependence of the yield-stress of mono-and poly-crystalline a-brasses containing 5 to 35 atyo zinc in the range 4 to 300 K is analysed in terms of the kink-pair model of solid-solution hardening. The parameter W, in the theoretical relation t = to exp ( -mkT/W,), where m is a constant equal to about 25, is evaluated for each composition of brasses from the slope of the In t / Tline drawn through data points. A peak is observed at about 27 atyo zinc in the correlation of W, with solute concentration c. The decrease in the value of W, with increase in c beyond 27 a t yo zinc seems to be associated with short-range order in the vicinity of dislocation cores. Mit dem Knotenpaarmodell der Mischkristallhiirtung wird die Temperaturabhangigkeit der FlieBspannung von ein-und polykristallinem a-Messing mit 5 bis 35 at% Zink im Bereich von 4 bis 300K analysiert. Der Parameter W, in der theoretischen Beziehung t = to esp (-mkT/W,), wobei m eine Konstante ist (= 25), wird fiir jede Messingzusammensetzung aus dem Anstieg der In t / T -Kurve durch die MeBpunkte berechnet. Ein Maximum wird bei etwa 27 at% Zink in der Korrelation von Vo mit der Konzentration c beobachtet. Der Abfall von W , mit dem Anstieg von c oberhalb 27 at% Zink scheint mit der Nahordnung in der Niihe von Versetzungskernen verkniipft zu sein.

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A discussion of optical properties of mixed oxides InuO3-SnO2 system is presented. Film thickness, substrate temperature, composition (in molar %) and annealing have a profound effect on the structure and optical properties of these films. Initially the increase in band gap with the increase of SnO2 content in In203is due to the increase in carrier density as a result of donor electrons from tin. The decrease in band gap above the critical Sn content is caused by the defects formed by Sn atoms, which act as carrier traps rather than electron donors. The increase in band gap with film thickness is caused by the increase in free carrier density which is generated by (i) Sn atom substitution of In atom, giving out one extra electron and (ii) oxygen vacancy acting as two electrons donor. The decrease in band gap with substrate temperature and annealing is due either to the severe deficiency of oxygen, which deteriorate the film properties and reduce the mobility of the carriers, or to the formation of indium species of lower oxidation state (INS+).