The Isothermal Oxidation Behavior of a Ti3Al-Nb-V-Mo Alloy
The isothermal oxidation behavior of Ti-24Al-14Nb-3V-0.5Mo alloy in synthetic air from 700°C to 1000°C was studied. The main emphasis was focused on the effect of microstructure obtained by different processes of melting and hot rolling, i.e. large and duplex of 2+B2, on the oxidation resistance. Regardless of the microstructure, the overall oxidation process of the specimens exposed at 700°C was dominantly controlled by the beneficial effect of Nb-addition due to the formation of a continuous -Al2O3 layer in the scale. However, both specimens showed poor oxidation resistance above 900°C, especially for the as-rolled specimen, because of higher volume fraction of the 2-phase. The spallation occurred in both specimens at 1000°C, which was probably relative to the formation of Ti2AlN between the thick scale and the substrate except for the TiO2 and -Al2O3.
Mechanical properties and oxidation behavior of the Ti–24Al–14Nb–3V–0.5Mo alloy sheet
Abstract Tensile properties of the Ti–24Al–14Nb–3V–0.5Mo alloy (at.%) solution treated at 1000 °C after hot-rolling was studied in the temperature range between room temperature and 700 °C. The tensile strength was sensitive to the test temperature and was decreased as the temperature increased from 200 to 500 °C. Tensile strength of the alloy at room temperature initially increased gradually with an increase in the strain rate from 8.3 × 10−4 to 0.33 s−1 followed by a slow hardening with increasing the strain rate to 8.3 × 10−1 s−1. The alloy exposed at 700 °C showed the best oxidation resistance due to the formation of a continuous α-Al2O3 layer in the scale. However, the beneficial doping effect of Nb addition on the oxidation resistance above 700 °C was probably overlaid by fast internal diffusion of oxygen, which was proved by a thick transitional layer beneath the scale in the specimen exposed at 800 °C.
Testosterone levels, handedness and sex ratio at birth.
Geschwind has hypothesized that levels of androgens in utero affect postnatal laterality preferences, high levels being associated with left-handedness of offspring. I have hypothesized that high parental androgen levels at the time of conception are associated with subsequent male births. However, left-handed parents seem to produce an excess of female, not male, offspring. This finding could be reconciled with the two hypotheses if individuals who were exposed to high levels of androgens in utero had low circulating levels in adulthood. Some evidence for this loophole is reviewed here. Lyster & Lloyd (1987, J. theor. Biol. 126, 125) have reported that (consistent with the hypotheses) index left-handed men have an excess of brothers; but, contrary to the hypotheses, index left-handed women have an excess of sisters. Accordingly these authors proposed that left-handedness in females is associated not with high levels of androgen in utero, but with a "sensitivity" to it. If such sensitivity were associated with low androgen levels, it might explain an excess of sisters among the sibs of left-handed women. It is shown here that evidence in agreement with this hypothesis (though not discriminating between it and Geschwind's) suggests that the sex ratios of offspring of LH male x RH female and of RH male x LH female matings, are both low.