Microstructure and mechanical properties of metastable lath martensite wires in the Fe-Ni-Cr-Al-C system produced by melt spinning in rotating water

Metastable lath martensite (_L) phase wires with high strengths have been produced in the Fe-Ni-Cr-Al-C alloy system by melt spinning in rotating water. These wires have a circular cross section and a white lustre and the wire diameter is in the range of 100 to 140m. The width and length of each lath in the_L phase are as small as about 0.3 and 2m, respectively. The_y,_f and_p are about 900 and 1650 MPa and 2.0% for the_L wires. The subsequent annealing causes an increase in _p as well as _y and _f and the attained values are about 1000 and 1700 MPa and 3.0% for Fe-10Ni-10Cr-6.5 Al-1.0C wire annealed at 773 K for 1 h owing to the precipitation strengthening of a very fine unidentified carbide and to a high density of dislocations and lath boundaries in the_L phase. Further annealing causes a significant decrease in _p through decomposition of_L to+M₇C₃+M₂₃C₆. Therefore, the high strength combined with relatively good ductility for the_L wires is interpreted as due to the suppression of the phase transformation of_L to a mixed structure of+M₇C₃+M₂₃C₆ by melt quenching.