Microstructural evolution of Mn-based maraging steels and their influences on mechanical properties

Predicting microstructure and strength of maraging steels: Elemental optimisation

“…However, small variations in d lath have been observed in a variety of maraging steels with different Ni and Mn content, even for tempered conditions [14,20,25,26,39]; this behaviour can be due to the relatively low lattice distortion and high solubility of substitutional atoms in Fe with respect to C atoms; hence, based on these experimental results, it is considered that d lath = 250 nm remains constant for all steels tested. For this case, ρ ≈ 3.6 × 10 14 m −2 , being this prediction consistent with experimental estimations in a stainless maraging steel [40].…”

“…No carbon content in Fe8Ni8Mn was reported [24]. Coarse TiC particles were observed in Lean7Mn, Lean10Mn and Lean12Mn in as-quenched conditions, having volume fraction of 0.22% and a mean size of 500 nm; nevertheless, Qian [25] concluded that they have no influence on hardening due to their size. Similarly, carbide formation in 17-4 SS has been reported [26]; Viswanathan et al [27] have explored their effects in strengthening, concluding that it is low.…”

“…1(a)). This mechanism is valid if the equilibrium volume fraction is high enough to fully transform the α′ laths into austenite; however, if the equilibrium volume fraction of γ (f γ,eq ) at a given ageing temperature is lower, then r γ and L γ are lower than d lath and d block by a factor of , respectively [25]; this is to account for the growth restriction effect on each direction of the austenite laths. Since the phase transformation is interface-controlled, the thickness and length evolution of γ can be prescribed by standard grain boundary kinetics equations [43]:…”

“…In all cases, Γ γ strongly depends on chemical composition. For instance, Qian [25] has found experimen Table 2 Intermetallics usually observed in multicomponent maraging steels.…”

“…Schober et al [53] observed in Fe Ni Al Mo the formation of -NiAl. 2 Small additions of Ti partition into NiAl forming Ni 2 AlTi in Fe Ni Mn Al Ti when nickel content is low (≤4 wt%) [4,25,54], whilst very low amounts of Mn atoms partition into the precipitates. No Mo partitioning to NiAl and its variants in 1 Although BCC-Cu is not an intermetallic phase, the same evolution descriptions will be adopted for all precipitates.…”