Effect of 0.25 and 2.0 MeV He-Ion Irradiation on Short-Range Ordering in Model (EFDA) Fe-Cr Alloys

Abstract

The effects of He + irradiation on a distribution of Cr atoms in 10.75, 15.15) alloys were studied by 57 Fe Conversion Electron Mӧssbauer Spectroscopy (CEMS). The alloys were irradiated with doses up to 12 x10 16 ions/cm 2 with 0.25 and 2.0 MeV He + ions. The distribution of Cr atoms within the first two coordination shells around Fe atoms was expressed with short-range order parameters 1 (first-neighbour shell, 1NN), 2 (secondneighbour shell, 2NN) and 12 (1NN+2NN). In non-irradiated alloys 1>0 and 2<0 was revealed for all three samples. The value of 120, i.e. the distribution of Cr atoms averaged over 1NN and 2NN, was random. The effect of the irradiation of the Fe94.2Cr5.8 alloy was similar for the two energies of He + viz. increase of number of Cr atoms in 1NN and decrease in 2NN.Consequently, the degree of ordering increased. For the other two samples, the effect of the irradiation depends on the composition, and is stronger for the less energetic ions where, for Fe89.25Cr10.75 alloy, the disordering disappeared and some traces of Cr clustering appeared. In Fe84.85Cr15.15 alloy the clustering was clear. In the samples irradiated with 2. 0 MeV He + ions the ordering also survived in the samples with x=10.75 and 15.15, yet its degree became smaller than in the Fe94.2Cr5.8 alloy.2

Mössbauer Spectrometry of Model Binary Fe100−xCrx (1 ≤ x ≤ 50) Alloys

“…[1][2][3] It is apparent that in various alloys, chromium has anticorrosion properties because of formation of surface segregation and passivation layer. [4][5][6][7] That is why stainless steels with high amount of chromium are suitable candidates for constructions of nuclear reactor pressure vessels. To study the microstructure of steels, Mössbauer spectroscopy (MS) is especially suitable.…”

Kinetics of phase separation, border of miscibility gap in Fe–Cr and limit of Cr solubility in iron at 832 K

“…, where X=B or CS, X m is a change of X caused by one Cr atom present in 1NN (m=1) or in 2NN (m=2). This procedure has already proved to properly work in the analysis of Mössbauer spectra registered on various Fe-based binary alloys including Fe-Cr ones e. g. [11][12][13][14][15][16][17][18][19][20]. The total number of possible atomic configurations (m,n) in the 1NN-2NN approximation is equal to 63.…”

“…As free parameters were also regarded X(0,0), line width (common to all sextets), G, B 1 , B 2 , and an angle between the magnetization vector and normal to the sample's surface, theta. On the other hand, based on our previous studies values of CS 1 = -0.02 mm/s, and CS 1 = -0.01 mm/s, were kept constant [18]. Using this procedure all measured spectra could have been well fitted with the average values of: B(0,0)=333( 2 Selected examples are displayed in Fig.…”

“…kGs. This value can be further used for determining a position of the extended miscibility gap line at 858 K. Towards this end can be used a linear relationship between <B> and Cr content, x, for binary Fe-Cr [18,19]. By doing so, one arrives at The second stage of the transformation process can be associated with a formation of the -phase.…”

Microstructure of High‐Chromium Ferritic–Martensitic Steels for Next‐Generation Reactors

“…Both effects can be explained based on the crystallographic phase diagram of the Fe-Cr system. [29][30][31][32][33][34][35][36][37][38][39][40] The investigated steel NS219 is a high-chromium ferritic-martensitic steel, which excels in mechanical resistance, corrosion resistance, and high hardness due to the presence of chromium carbides. NS219 steel is therefore suitable candidate (in the future development) for applications where the mechanical and chemical resistance of the surface is emphasized.…”