The viscosity of Zr[subscript 41.2]Ti[subscript 13.8]Cu[subscript 12.5]Ni[subscript 10.0]Be[subscript 22.5] (Vit1) has been measured above the liquidus
temperature, T[subscript liq]=1026 K, using a high vacuum high temperature rapid annealing
furnace equipped with a Couette Concentric Cylinder Rheometer. Steady state
measurements have been taken over a temperature range of 1075-1300 K and a shear rate
range of 10⁰-10² s⁻¹. It has previously been discovered that there exists a pronounced
decrease in viscosity with increasing shear rate which is contrary to the general belief that
metallic systems above the liquidus temperature should show Newtonian behavior due to
high atomic mobility. This suggests that there is short or medium range order present in
the liquid state that can be destroyed by shearing. This current study has discovered that
this shear rate dependence of the viscosity of Vit1 decreases with increasing temperature
and approaches the Newtonian behavior and viscosities of simple monatomic or binary
liquid alloys at 1225 K. Once this state is reached the viscosity will remain Newtonian in
the liquid state and no order is reformed until the sample is cooled into the supercooled
region. This indicates a strong temperature history dependence of the viscosity. It has
also been discovered that initially crystalline Vit1 has an order of magnitude lower
viscosity than initially amorphous Vit1 at 1075 K after melting. This difference
decreases with increasing temperature until similar viscosities are obtained at 1175 K.
The Vogel-Fulcher-Tammann relationship shows decreasing fragility of Vit1 with
increasing shear rate and increasing temperature. It was also seen that temperature has a
larger and more permanent effect on the fragility than shear rate. The development and
results of converting viscosity data to configurational entropy using the Adam-Gibbs
entropy model for viscous flow are discussed. This shows that the configurational
entropy present after melting is on the order of the entropy of fusion. / Graduation date: 2006
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28598 |
| Date | 09 December 2005 |
| Creators | Way, Christopher D. |
| Contributors | Busch, Ralf |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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