HIGH-TEMPERATURE TENSILE PROPERTIES OF W-RE-THO2 ALLOYS

The tensile properties of W-Re-1wt.%ThO2 alloys with rhenium concentrations of 0-26wt.% were examined in a temperature range 1600-2600 K. The effects of rhenium concentration, testing temperature and strain rate on the strength properties and deformation behavior of these alloys were investigated. It was found that rhenium had a moderate strengthening effect of the thoriated tungsten at temperatures up to about 2000 K. In the temperature range 2000-2600 K, rhenium concentrations above 11 wt.% in the thoriated tungsten resulted in a strength degradation instead of strengthening owing to rhenium-introduced structural instability. The addition of rhenium increased both the temperature sensitivity and the strain rate sensitivity of the thoriated tungsten at high temperatures. The post-test specimens were characterized by scanning electron microscopy and transmission electron microscopy. The dominant deformation mechanism was the cross-slip of screw dislocations when deformation occurred in the temperature range 1600-2000 K and was grain boundary sliding when deformation occurred at temperatures above 2000 K. An examination on the fracture surfaces of the tensile-fractured specimens showed that the fracture mode of the W-Re-1wt.%ThO2 alloys experienced a transition from transgranular to intergranular with either increasing temperature or increasing rhenium concentration.