Thread Content
Taking into account the previously described principles regarding how irradiation causes microscopic damage to metals, irradiation can alter the macroscopic properties of metals in multiple aspects—mechanical, physical, and chemical. The specific effects are as follows: Changes in mechanical properties. Irradiation hardening: The dislocation loops and defect clusters generated by irradiation impede the movement of dislocations, thereby significantly increasing the hardness and yield strength of metals. For instance, after irradiation, the surface hardness of SKH51 tool steel can be considerably enhanced. Irradiation embrittlement: Metal plasticity and fracture toughness decrease significantly, while the ductile-to-brittle transition temperature rises; the risk of brittle fracture in reactor pressure vessel steel increases markedly after long-term irradiation. It can also cause irradiation creep and a deterioration in fatigue performance; the fracture elongation of austenitic stainless steels decreases significantly after irradiation. Changes in physical properties: Irradiation leads to a decrease in the electrical and thermal conductivity of metals. It also causes irradiation swelling; as vacancies accumulate and form voids, the metal undergoes irreversible volume expansion. At high doses, the swelling rate of stainless steel can exceed 100%, thereby directly destroying the dimensional accuracy of the components. Changes in chemistry and corrosion resistance: Irradiation induces element segregation within metals as well as changes in their phase structure, which significantly increases the susceptibility of materials such as stainless steel to stress corrosion cracking induced by irradiation. It also leads to phenomena such as radiation oxidation and radiation corrosion, accelerating the failure of these materials over time.