Different Mechanisms of ε-M and α′-M Variant Selection and the Influencing Factors of ε-M Reversion During Dynamic Tension in TRIP Steel

doi:10.1007/s40195-017-0651-y

Abstract

Abstract:

The variant selection of martensites (ε-M and α′-M) and ε-M reversion in dynamic tensile high-manganese TRIP steel were investigated. α′-M variant pairs with a zigzag morphology frequently formed, and the pairs of neighboring α′-M variants were examined in terms of mechanical work and strain energy reduction. The occurrence of a primary α′-M variant is determined by mechanical work, but high products of mechanical work and strain energy reduction are essential for secondary variant selection. In contrast to α′-M variant pair selection, ε-M variant selection can be attributed to the highest mechanical work. During ε-M→α′-M transformation, the mechanical work of ε-M reversion is higher than that of α′-M variant, thereby implying that ε-M reversion in 〈110〉 _γ grain is possible. ε-M plate distribution also affects the feasibility of ε-M reversion.

Key words: TRIP-assisted steel, Dynamic plastic deformation, Martensitic transformation, Variant, selection, Orientation relationship

Li-Na Wang, Ping Yang, Ting Jin, Wei-Min Mao. Different Mechanisms of ε-M and α′-M Variant Selection and the Influencing Factors of ε-M Reversion During Dynamic Tension in TRIP Steel[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(5): 449-455.

Figures/Tables 6

Fig. 1 Microstructure of TRIP steel: a before deformation, b after deformation, c enlarged view of zigzag-type α′-M variant pairs after deformation

Fig. 2 Orientation maps and pole figures of grain A (a deviated 〈111〉γ grain) during tension at a strain rate of 1600 s-1(TD-tensile direction): a orientation map I (gray color—γ, red color—ε-M, blue color—α′-M), b orientation map II (gray color—γ, red color—ε-M, Euler angles—α′-M), c pole figures of γ, ε-M, and α′-M

Fig. 3 a Calculated mechanical works of four ε-M variants in grain A, b calculated mechanical works and P value of six α′-M variants in grain A

Fig. 4 Orientation maps and pole figures of grain B during tension at strain rate of 1.2 × 103 s-1 (TD-tensile direction): a orientation map I (gray color—γ, red color—ε-M, blue color—α′-M), b orientation map II (Euler angles color—γ, gray color—ε-M, blue color—α′-M), c orientation map III (gray color—γ, Euler angles color—ε-M, blue color—α′-M, red line—\(\langle 11\bar{2}0\rangle\)86° misorientation), d pole figure of γ, e pole figure of ε-M

Fig. 5 Calculated mechanical works in grain B: a four ε-M variants, b six α′-M variants in ε1 (V1-V6), c six α′-M variants in ε 3 (V13-V18)

Fig. 6 Orientation maps and pole figures of grains C and D during tension at a strain rate of 1.6 × 103 s-1(TD-tensile direction): a orientation map I of grain C (Euler angles color-γ, red color-ε-M, blue color-α′-M), b orientation map II of grain C (gray color-γ, Euler angles color-ε-M, blue color-α′-M, red line-\(\langle 11\bar{2}0\rangle\)86° misorientation), c orientation map I of grain D (gray color-γ, red color-ε-M, blue color-α′-M), d Orientation map II of grain D (gray color-γ, Euler angles color-ε-M, blue color-α′-M), e pole figures of γ and ε-M in grain C, f pole figures of γ and ε-M in grain D

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