It has been well known that the boundary fracture strength of molybdenum depends strongly on factors such as grain boundary character and impurity segregation (C and O). In order to clarify the influence of grain boundary geometrical and chemical factors on the boundary fracture strength of molybdenum, bicrystals with a 〈001〉 symmetric tilt boundary were prepared in a range of misorientation angles φ from 0° to 90°, and the boundary fracture strength was measured for not-purified and purified specimens by a four-point bending test. In addition, misorientation dependence of the grain boundary energy was measured by a thermal grooving method, and the correlation between the grain-boundary energy and the boundary fracture strength for purified specimens was also investigated. The main results obtained here are as follows. (1) The grain-boundary energy depends remarkably on the misorientation angle. Large energy cusps were observed at the near 36.9°/(13̄0) and 53.1°/(12̄0) Σ5 coincidence tilt boundaries, and small energy cusp was observed at the near 22.6°/(15̄0) Σ13 coincidence tilt boundary. (2) For the purified specimens, the boundary fracture strength depends on its misorientation angles φ. However, for the not-purified specimen, the misorientation dependence was not observed at large angle boundaries in the range of φ from 16° to 54°. (3) The conspicuous difference in the boundary fracture strength between the not-purified and purified specimens was not recognized. It is concluded that the influence of impurity atoms (C and O) on the boundary fracture strength was relatively small for the 〈001〉 symmetric tilt boundaries. (4) A relatively good correlation was obtained between the grain boundary energy and the boundary fracture strength in the 〈001〉 symmetric tilt boundary.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanics of Materials
- Metals and Alloys
- Materials Chemistry