By use of the vibration technique, viscosities of Pd84Si16 alloy and Pd78Cu6Si16 alloy were measured over the temperature range from 1150 to 1500 K. The viscosity was represented by log(η⁄Pa·s)=4.21+2.53×103⁄T for Pd84Si16 alloy and log(η⁄Pa·s)=−4.23+3.51×103⁄T for Pd78Cu6Si16 alloy. The temperature dependence of the viscosity of undercooled liquid was estimated by using Cohen-Turnbull’s expression and if the viscosity at the glass transition temperature was of 1010 Pa·s, it was shown by log(η⁄Pa·s)=−3.42+8.58×102⁄(T−551) for Pd84Si16 alloy and log(η⁄Pa·s)=−3.23+1.33×103⁄(T−520) for Pd78Cu6Si16 alloy. Using these results, the T-T-T curves were calculated in the case of mechanism of homogenious nucleation and growth. The critical cooling rates obtained from these T-T-T curves coincided with the directly measured critical cooling rates, and it was concluded that the glass formation was affected mainly by the liquidus temperature and the viscosity of liquid. Finaly the effect of viscosity on glass formation was discussed from the standpoint of a cluster formation in liquid.
