An intermetallic forming steel under radiation for nuclear applications

Abstract

In this work we investigate the formation and stability of intermetallics formed in maraging steels under ion beam radiation utilizing nanoindentation, microcompression testing and atom probe tomography. A comprehensive discussion analyzing the findings utilizing rate theory is introduced, comparing the aging process to radiation induced diffusion. New findings of radiation induced segregation of undersize solute atoms (Si) towards the precipitates are considered.Structural materials in nuclear applications suffer a wide range of microstructural changes under radiation. Consequences of these microstructural and microchemical evolutions are increased hardening, embrittlement, enhanced rates of subcritical cracking, low-temperature irradiation creep, void swelling, loss of ductility and creep resistance [1][2][3][4].The formation of cascades and the formation of a large number of point defects due to particle interaction with materials cannot be avoided initially. However, recent studies have shown that the collection of point defects into voids or clusters can be delayed or avoided by trapping the initial defects at a large number of defect sinks where the defects then annihilate, preventing their accumulation within the lattice [5][6][7][8]. The most effective defect sinks and traps have been proven to be interfaces such as grain boundaries or phase boundaries [5][6][7][8]. This information has led to the creation of materials with extremely high interface densities which allow for a more radiation tolerant system by utilizing a high density of nm-sized precipitates or multilayer structures [9][10][11]. The influence of these precipitates or multilayers on the mechanical properties and radiation resistance of the material is controlled by parameters like size, shape, number density or layer thickness and volume fraction. One well known example of this approach are Nanostructured Ferritic Alloys (NFAs), where extremely large numbers of nanoscale oxide particles (in the range of 10 23 -10 24 m -3 in number density) are present. These materials are also known as mechanically alloyed oxide dispersion strengthened (ODS) steels [12]. Another example is the widely studied immiscible fcc/bcc metallic 3 multilayers such as Cu/Nb multilayers realized by physical vapor deposition (PVD) coating techniques or roll bounding [13,14]. This microstructure allows the radiation induced point defects or nuclear reaction products to "heal" or become trapped at interfaces. These materials are usually considered top down structures where the manufacturer creates these materials from powders or sputter targets and consolidates those during processing. This leads to the fact that the resulting microstructure can rarely be changed after materials synthesis. NFAs after processing into tubes or thin plates have been shown to be strongly textured with anisotropic properties formed during processing while the Cu/Nb layers are by nature anisotropic. Post processing heat treatment usually does not change the structure any more due to the fact t...

Rate Theory Model of Irradiation-Induced Solute Clustering in b.c.c. Fe-Based Alloys

“…The sign of this numerator indicates the direction of temperature sensitivity. Specifically, if the sum ( as is the case for Fe-9%Cr ODS (À3:1 þ 2:2 þ 0:68 ¼ À0:22 eV) 29,35 and HCM12A (À2:48 þ 1:65 þ 0:68 ¼ À0:15 eV), 23,35,36 higher irradiation temperature will result in larger nanoclusters. However, if this numerator is positive, nanocluster size as a function of temperature will exhibit the opposite trend.…”

A high temperature mechanical study on PH 13-8 Mo maraging steel

“…It appears that the matrix strength follows from a careful balance between matrix softening and precipitate strengthening, because in this material no softening and even a slight strengthening is observed up to 450°C. The precipitate strengthening has been previously studied from 450 to 600°C by APT, and recently, it has been demonstrated at RT that under ion beam irradiation precipitate precursors can be formed [13]. No studies have shown the formation of β-NiAl precipitates below the 450°C.…”

“…Precipitation hardening on PH 13-8 has been previously studied by atom probe tomography (APT), transmission electron microscopy (TEM), x-ray diffraction (XRD), Vickers hardness and tensile tests [4,[7][8][9][10][11]. In addition, different surface treatments have also been studied on this steel such as plasma nitriding [3,12] and carburing [12], and recently under ion irradiation [13]. However, the mechanical properties at high temperature have not been investigated yet.…”

Экспериментально-теоретическое исследование эволюции атомной структуры высокоэнтропийных сплавов на основе Fe, Cr, Ni, Mn и Co при термическом и радиационном старении

“…Al 0.5 CoCrCuFeNi имеет высокое сопротивление усталости [21], а оба CoCrFeNiTi и AlCoCrFeNiTi имеют отличную износостойкость [22]. Также было показано, что сплав Кантора и аналогичные ВЭС имеют высокую устойчивость к процессам радиационно-индуцированной деградации, таким как распухание [23,24], упрочнение [24,25] и сегрегация [26]. Сплавы, с составом CoCrFeNi (CCFN), являются одними из наиболее изученных ВЭС.…”