A ferrite–austenite 12CrNi2 alloy steel additively manufactured by laser melting deposition(LMD) was heat treated by direct quenching(DQ) and tempering inter-critical quenching(TIQ) at 800 ℃ for enhancing its stren...A ferrite–austenite 12CrNi2 alloy steel additively manufactured by laser melting deposition(LMD) was heat treated by direct quenching(DQ) and tempering inter-critical quenching(TIQ) at 800 ℃ for enhancing its strength–ductility balance. Both heat-treated alloy steels have the martensite–ferrite dual-phase(DP) microstructures. The volume fractions of martensite in the two treated alloy steels are nearly similar(~ 85 vol%), while the sizes of the prior austenitic grain for martensite are different. The martensite-dominated DP microstructure resulted in an obvious improvement in strength–ductility balance of the alloy steel. Compared with the DQ treatment, the multi-step TIQ treatment caused the strength–ductility balance of the alloy steel to be enhanced due to its higher total elongation. The better ductility of the TIQ-treated alloy steel can be attributed to the optimization of the microstructure. The preferred orientation of ferritic grain in the as-deposited alloy steel which was adverse to plastic deformation through dislocation slip was eliminated via the multi-step TIQ treatment. Moreover, the TIQ treatment promoted the formation of finer-grained martensite with larger areas of grain boundaries and twinning boundaries which resulted in the enhancement of the coordinated deformability of the martensite with the ferrite.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2016YFB1100203)。
文摘A ferrite–austenite 12CrNi2 alloy steel additively manufactured by laser melting deposition(LMD) was heat treated by direct quenching(DQ) and tempering inter-critical quenching(TIQ) at 800 ℃ for enhancing its strength–ductility balance. Both heat-treated alloy steels have the martensite–ferrite dual-phase(DP) microstructures. The volume fractions of martensite in the two treated alloy steels are nearly similar(~ 85 vol%), while the sizes of the prior austenitic grain for martensite are different. The martensite-dominated DP microstructure resulted in an obvious improvement in strength–ductility balance of the alloy steel. Compared with the DQ treatment, the multi-step TIQ treatment caused the strength–ductility balance of the alloy steel to be enhanced due to its higher total elongation. The better ductility of the TIQ-treated alloy steel can be attributed to the optimization of the microstructure. The preferred orientation of ferritic grain in the as-deposited alloy steel which was adverse to plastic deformation through dislocation slip was eliminated via the multi-step TIQ treatment. Moreover, the TIQ treatment promoted the formation of finer-grained martensite with larger areas of grain boundaries and twinning boundaries which resulted in the enhancement of the coordinated deformability of the martensite with the ferrite.
