Development of high strength hot rolled low carbon copper-bearing steel containing nanometer sized carbides

A Review on Nano-Scale Precipitation in Steels

“…Finally, the paper is wrapped up with the challenges and the future directions of nano-scale precipitate strengthened steels. [28] (Fe,Mn) 3 AlC 0.38 [6], (Fe,Mn) 3 AlC 0.51 [6] M 2 C carbides Hexagonal [18] (Mo,Cr) 2 C [17]; (Mo,Cr,V) 2 C [30] Co-located with Cu on lath boundaries and dislocations [17] Rod (coherent) [17]; Irregular (incoherent) [17] Ni 3 Ti Hexagonal (DO 24 ) [36,37] → L1 2 [37] → FCC [37] (Ni,Fe,Co) 3 (Ti, Mo) [14] Homogeneously throughout matrix, heterogeneous nucleation on interphases, dislocations and grain boundaries [36] Disc and rod [14,36] NiAl B2 [3,15] Ni, Al, Mn, Fe, Cu [15,35]; Ni, Al, Fe, Mn [2]; Ni(Al,Fe) [3]; Ni, Al, Fe, Cr, Mo [38] Co-located with Cu [15]; Mostly homogeneously distributed in matrix and some elongated particles on dislocations [3] Spherical [2,3] [7] Cu and (Ti,Mo)C Fe-1.53Mn-1.17Cu-0.34Si-0.21Mo-0.09Ti-0.04Al-0.07C 732 13 [16] * Monzen et al [21] argued that the B2 to 9R transformation depends on the surrounding temperature. At 500 • C, the transformation occurs at 12 nm instead of 4 nm.…”

“…A compilation of (a) yield strength increment and (b) ductility change against precipitate number density of various precipitate strengthened steels. TiC [40] Ni3Ti [14] Cu + NiAl -4%Ni [1] Cu + NiAl -2.5%Ni [1] NiAl -3%Mn [2] NiAl -no Mn [2] NiAl [3] Cu + NiAl [15] Cu + (Ti,Mo)C [16] (Ti,Mo)C [16] Cu + M2C [17] TiC [29] (Ti,Mo)C [29] Cu [33] K carbide [26] k carbide [7] Cu -no Ni [4] Cu -0.75%Ni [4] k carbide [27] NiAl [39] (a)…”

“…Again, no reduction of the uniform elongation was observed, suggesting a small increment (0.6 nm in diameter) in the size of precipitates while maintaining a high number density (in the order of 10 24 m −3 ) through nano-scale-co-precipitation can produce a large strength improvement (43% increase from 434 MPa to 622 MPa) at no expense of ductility. On the contrary, Ni3Ti [14] Cu + NiAl -4%Ni [1] Cu + NiAl -2.5%Ni [1] NiAl -3%Mn [2] NiAl -no Mn [2] NiAl [3] Cu + NiAl [15] Cu + (Ti,Mo)C [16] (Ti,Mo)C [16] TiC [29] (Ti,Mo)C [29] k carbide [7] k carbide [27] NiAl [39] (b) Figure 3. A compilation of (a) yield strength increment and (b) ductility change against precipitate size of various precipitate strengthened steels.…”

“…The BCC to 9R transformation and the change of slip planes during the shearing of Cu precipitates might also contribute to the enhanced ductility. The intrinsic soft nature of Cu precipitates that allow for an easy cut through by dislocations can be another factor contributing to the improved ductility [16].…”

“…Some recently investigated precipitates [2][3][4]7,[14][15][16][17][18] in steels from year 1987 to 2017 are listed in Table 2. These nano-scale precipitates are metastable.…”