Precipitation strengthening of ductile Cr 15 Fe 20 Co 35 Ni 20 Mo 10 alloys

A high-entropy alloy with hierarchical nanoprecipitates and ultrahigh strength

“…The high strength of the as-cast bcc TaHZrTi refractory HEA is due to the high-load transfer ability of bcc refractory HEAs ( 29 ). The strengthening mechanism in the precipitation-strengthened HEAs is dominated by the shearing mechanism ( 26 , 28 ). The uniqueness of precipitation strengthening in the Fe 25 Co 25 Ni 25 Al 10 Ti 15 HEA is due to the hierarchical precipitate spatial distribution, which is not found in precipitation-strengthened HEAs reported in the literature.…”

“…The uniqueness of precipitation strengthening in the Fe 25 Co 25 Ni 25 Al 10 Ti 15 HEA is due to the hierarchical precipitate spatial distribution, which is not found in precipitation-strengthened HEAs reported in the literature. In previously reported HEAs, dislocations only need to shear coherent γ′ precipitates ( 26 , 28 ). Here, dislocations must shear both the γ′ (primary precipitates) and the γ* (secondary nanoprecipitates).…”

Engineering heterostructured grains to enhance strength in a single-phase high-entropy alloy with maintained ductility

“…To date, the reported superior mechanical properties of HEAs, have been achieved mostly with multi-phase structures, which are principally attributed to the presence of second phases and phase metastability induced strengthening [2,[4][5][6][7][8][9][10]. Comparing with multi-phase HEAs, it is more difficult to attain a good combination of strength and ductility in single-phase HEAs at room temperature, particularly for single-phase fcc HEAs [2,11].…”

“…Extensive efforts have been undertaken to strengthen single-phase fcc HEAs; these include: Carbon-and Boron-doping strategies [8,17], introducing coherent precipitates [13] and introducing brittle intermetallic [7] into the fcc matrix, as well as various grain refinement strategies [18]. With the exception of the grain refinement approach, other strategies invariably lead to alloys that are not single-phase fcc, thereby leading to complex HEA matrices.…”

“…In order to provide insight into the mechanical behaviour of the HS single-phase fcc Fe 29 Ni 29 Co 28 Cu 7 Ti 7 HEA, the yield strength versus failure strain and the ultimate tensile strength versus failure strain are plotted in Figure 5 alongside other single-phase fcc HEAs/MEAs and enhanced fcc HEAs/MEAs [7][8][9]11,13,16,17,19,27,28]. It is worth mentioning that the enhanced fcc HEAs/MEAs refer to the alloys using C- [17] and B-doping [8], coherent precipitation strengthening [9,13,28] and brittle intermetallic strengthening [7], as well as grain refinement strategies [19], to strengthen a fcc HEA/MEA matrix. As shown in Figure 5(a), the yield strength of the HS Fe 29 Ni 29 Co 28 Cu 7 Ti 7 HEA, which is comparable with those of some enhanced fcc HEAs/MEAs, is much higher than those of the single-phase fcc HEAs/MEAs.…”