Integrated effect of thermal ageing and low flux irradiation on microstructural evolution of the ferrite of welded austenitic stainless steels
Journal article, 2021

With the purpose to quantify microstructural changes with respect to ageing degradation, the microstructure of aged type 308 stainless steel welds with a ferrite content of 5-7% has been analysed using atom probe tomography. The weld metal of the core barrel of a decommissioned light water reactor, irradiated during operation of the reactor to 0.1 dpa, 1 dpa and 2 dpa at 280-285°C (231,000 h), are compared to two similar thermally aged welds. In the ferrite of the irradiated welds, there is spinodal decomposition into Cr-rich α’ and Fe-rich α, with a similar degree of decomposition for all investigated doses, amplitudes of 21-26% and wavelengths between 6 and 9 nm. The ferrite of the thermally aged material showed evidence of decomposition when aged at 325°C (an amplitude of 13-14% and wavelength of 5 nm), but not when aged at 291°C, thus the irradiation significantly increases the rate of spinodal decomposition. There is G-phase (Ni Si Mn ) precipitation in the ferrite of all the weld metals except the one that was thermally aged at the lowest temperature. After irradiation to 1 and 2 dpa, the G-phase is considerably more well developed than after 0.1 dpa or thermal ageing.

Thermal aging

Neutron irradiation


Austenitic welds

Atom probe tomography

Delta ferrite

Spinodal decomposition


Kristina Lindgren

Chalmers, Physics, Microstructure Physics

Martin Bjurman


Royal Institute of Technology (KTH)

P. Efsing

Ringhals AB

Royal Institute of Technology (KTH)

Mattias Thuvander

Chalmers, Physics, Microstructure Physics

Journal of Nuclear Materials

0022-3115 (ISSN)

Vol. 551 152967

Subject Categories

Manufacturing, Surface and Joining Technology

Other Physics Topics

Metallurgy and Metallic Materials

Areas of Advance


Materials Science


Chalmers Materials Analysis Laboratory



More information

Latest update