Effect of thorium additions on metallurgical and mechanical properties of Ir-0. 3 pct W alloys

Journal Article · Mon Jun 01 04:00:00 EDT 1981 · Metall. Trans., A; (United States)

DOI:https://doi.org/10.1007/BF02643480· OSTI ID:5687211

Liu, C T; Inouye, H; Schaffhauser, A C

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/sup 0/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/sup 0/C. Intergranular fracture in the doped alloys is suppressed 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.

• Research Organization: Oak Ridge National Lab., TN
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5687211
• Journal Information: Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 121; ISSN MTTAB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ACTINIDE ALLOYS
ALLOYS
CRYSTAL STRUCTURE
DUCTILITY
FRACTURE PROPERTIES
GRAIN BOUNDARIES
GRAIN SIZE
HEAT TREATMENTS
IMPACT STRENGTH
IRIDIUM ALLOYS
IRIDIUM BASE ALLOYS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALLURGY
MICROSTRUCTURE
PLATINUM METAL ALLOYS
SIZE
SOLUBILITY
STRESS ANALYSIS
TENSILE PROPERTIES
THORIUM ADDITIONS
THORIUM ALLOYS