Effect of Thorium Additions on Metallurgical and Mechanical Properties of Ir-0.3 pct W Alloys |
| |
Authors: | C T Liu H Inouye A C Schaffhauser |
| |
Affiliation: | (1) Oak Ridge National Laboratory, 37830 Oak Ridge, TN |
| |
Abstract: | Metallurgical and mechanical properties of Ir-0.3 pct W alloys have been studied as a function of thorium concentration in
the range 0 to 1000 ppm by weight. The solubility limit of thorium in Ir-0.3 pct W is below 30 ppm. Above this limit, the
excess thorium reacts with iridium to form second-phase particles. Thorium additions raise the recrystallization temperature
and effectively retard grain growth at high temperatures. Tensile tests at 650 °C show that the alloy without thorium additions
(undoped alloy) fractured by grain-boundary (GB) separation, while the alloys doped with less than 500 ppm thorium failed
mainly by transgranular fracture at 650 °C. Intergranular fracture in the doped alloys is supressed by GB segregation of thorium,
which improves the mechanical properties of the boundary. The impact properties of the alloys were correlated with test temperature,
grain size, and heat treatment. The impact ductility increases with test temperature and decreases with grain size. For a
given grain size, particularly in the fine-grain size range, the thorium-doped alloys are much more ductile and resistant
to GB fracture. All of these results can be correlated on the basis of stress concentration on GBs by using a dislocation
pileup model. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|