Small-angle neutron scattering quantification of phase separation and the corresponding embrittlement of a super duplex stainless steel after long-term aging at 300°C

Quantitative Nanostructure and Hardness Evolution in Duplex Stainless Steels: Under Real Low-Temperature Service Conditions

“…[18,22,37] Recently, Small-Angle Neutron Scattering (SANS) has been applied for quantitative bulk characterization of PS during long-term isothermal aging of a commercial grade super-duplex stainless steels (SDSS) at 300 °C. [36] This manuscript expands on that work and reports quantitative information on the compositional fluctuations taking place during PS at the nano-length scale for two commercial alloys at various industrially relevant service temperatures. The two commercial grades studied were the 22Cr-5Ni (also referred to as 2205 or UNS S32205) grade DSS and 25Cr-7Ni (also referred to as 2507 or UNS S32750) grade super-duplex stainless steel (SDSS).…”

“…Good fits were obtained with c ¼ 6. [ [36] Fits of Eq.2 to the SANS data (see Figure 4) are very good, and the fitting parameters give information on the physical parameters of interest. This approach can accurately identify the changes in the length scale and the concentration fluctuation amplitude during the phase separation process.…”

“…[26,33] Phase separation in commercial grade duplex alloys [9,14,17,22,34,35] has only been investigated to a limited extent, especially for test conditions emulating operando conditions, i.e., low temperatures where the embrittlement takes years. [17,36] Furthermore, there is a lack of comprehensive bulk characterization of PS and often measurements are made on a limited volume of the material using techniques such as atom probe tomography. [18,22,37] Recently, Small-Angle Neutron Scattering (SANS) has been applied for quantitative bulk characterization of PS during long-term isothermal aging of a commercial grade super-duplex stainless steels (SDSS) at 300 °C.…”

A comparative study of Fe-Cr unmixing using differential scanning calorimetry and small-angle scattering

“…As previously mentioned, all the aging conditions characterised here using DSC have already been characterised using SAXS -the material used for both techniques extracted from the same aged samples for each aging condition. Several authors have characterised the Fe-Cr compositions fluctuations appearing and developing during unmixing in terms of amplitude and characteristic length using APT (based on 1D autocorrelation function and radial distribution functions or RDFs more recently) [2,9,11,13,25,29]. In addition, we already showed that the RDFs extracted from APT datasets and from SAS data can be analysed in a common framework leading to an equivalent characterisation of the Fe-Cr composition fluctuations in terms of amplitude and characteristic length [31].Thus, we will use our SAXS measurements as Fe-Cr composition fluctuations reference descriptors to compare with the characteristics obtained from the DSC temperature scans.…”

“…Due to its very large impact on the industrial use of stainless steels, this Fe-Cr decomposition has been extensively studied over the past decades. Experimental characterization of the degree of unmixing has been mainly carried out using Atom Probe Tomography (APT) [2,4,[6][7][8][9][10][11][12][13][14][15] and Small-Angle Scattering (using neutrons or X-rays, respectively SANS and SAXS) [16][17][18][19][20][21][22][23][24][25]. These experimental data have extensively served as a basis for establishing the validity of physically-based models, most often using Kinetic Monte Carlo modelling, and for establishing the link between the degree of unmixing and the evolution of mechanical properties [2,4,9,15,24,[26][27][28][29][30].…”