Nitrogen-induced hardening in an austenitic CrFeMnNi high-entropy alloy (HEA)

Abstract

Nitrogen is a well-known gamma-stabiliser in austenitic steels, also responsible for significant solid solution hardening of these materials. Yet, only few papers have studied its impact on austenitic high-entropy alloy (HEA) matrixes. This study focuses on a cobalt-free, non equimolar CrFeMnNi HEA doped with nitrogen. A series of alloys was cast under a nitriding atmosphere to promote nitrogen absorption into the liquid alloy. Study of as-cast alloys has shown nitrogen presence in solid solution up to 0.3 wt. % (1.2 at. %). Over the whole range of compositions, a linear increase of hardness (134 HV/wt. % of N) was measured as well as an expansion of the lattice parameter of a/a= 1.01 / wt. % N due to nitrogen addition in the interstitial sites of the lattice. Tests on forged and annealed samples showed that the increase of hardness with nitrogen addition is higher than in as-cast state (210 HV / wt. % of N) surely due to presence of other strengthening mechanisms. Tensile tests confirmed that the presence of dissolved nitrogen increases yield strength and ultimate strength and enhances strain-hardening, without any modification of ductility.

CrMnFeCoNi high entropy alloys with carbon and nitrogen: mechanical properties, wear and corrosion resistance

“…The beneficial effect of N on the systems CoCrFeMnNi and CrFeMnNi has been also documented by Xiong et at. [20] and Traversier et al [21], respectively, which the authors associate with, solid-solution strengthening, precipitation strengthening, and grain refinement [20].…”

Manipulation of Microstructure and Mechanical Properties in N-Doped CoCrFeMnNi High-Entropy Alloys

“…Since the nitride precipitation is formed, we can assume that the matrix of N0.3 HEA has solute nitrogen atoms as maximum solubility. The maximum solubility of nitrogen in Cantor HEA is reported as 0.18 wt.% (~0.72 at.%) [41]. Therefore, the ∆σ S without the effect of precipitation can be calculated as~89.3 MPa.…”

Atomistic investigation of elementary dislocation properties influencing mechanical behaviour of Cr15Fe46Mn17Ni22 alloy and Cr20Fe70Ni10 alloy

“…Recent works have shown that some single-phase High Entropy Alloys (HEA) exhibit excellent mechanical properties, radiation-resistance properties and phase stability making them potential candidates for structural applications [1][2][3][4][5][6][7][8][9][10]. However, many authors have traced the origin of these properties to the specific behaviour of dislocations [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Face-Centered Cubic (FCC) HEA, such as Cantor alloy consisting of equimolar CoCrFeMnNi composition exhibits excellent mechanical properties and improved irradiation resistance [1].…”

“…Face-Centered Cubic (FCC) HEA, such as Cantor alloy consisting of equimolar CoCrFeMnNi composition exhibits excellent mechanical properties and improved irradiation resistance [1]. On the other hand, the presence of Cobalt excludes Cantor alloy from structural applications in nuclear reactors, due to the production of 60 Co radioisotope in in-service conditions [19,[29][30]. This is one of the reasons for the design of new Cofree HEA alloys, mainly from the CrFeMnNi family [19,[29][30][31][32][33][34][35].…”

“…On the other hand, the presence of Cobalt excludes Cantor alloy from structural applications in nuclear reactors, due to the production of 60 Co radioisotope in in-service conditions [19,[29][30]. This is one of the reasons for the design of new Cofree HEA alloys, mainly from the CrFeMnNi family [19,[29][30][31][32][33][34][35]. Currently, in the major types of nuclear reactor, the in-core components consist mostly of austenitic stainless steels (ASS) [36][37][38] and some authors [29,[36][37] have shown that ASS can be improved to exhibit better radiation damage resistance.…”