Influence of technological defects and neutron irradiation on the mechanical properties of single-crystal molybdenum pipes

Abstract

The state of single-crystal molybdenum pipes irradiated in an IVV-2M reactor at the peak temperature of 1400°C for 1700 and 3200 h by the fast neutron fluence of 3 × 10²⁰ and 5 × 10²⁰ n cm^–2, respectively, is investigated. The aim is to analyze the shape and surface state of pipes, the metallography of the structure, the short-time mechanical properties, and the character of destruction of the ring pipe specimen under testing. Radiation strengthening of molybdenum single-crystal is not registered. The strength parameters of the irradiated material are the level of initial values. The plastic properties of samples approach zero under room temperature tests. When the temperature is above 250°C, the total tensile strain of the sample exceeds 15% and ductile fracture with neck thinning to zero takes place. The perfect structure of an irradiated single crystal is preserved. Technological defects such as microcracks on the inner surface of pipes may act as stress concentrators.