Microstructures and Tensile Properties of Maraging Steel Processed by Equal-Channel Angular Pressing

Abstract

An 18Ni (C-250) maraging steel was successfully processed by equal channel angular pressing (ECAP) for a single pass at room temperature. Microstructural observations showed that the martensite laths of 18Ni maraging steel were elongated to more narrow bands with a width of 100-200 nm after ECAP deformation. After ageing treatment, many nano-sized precipitates distributed uniformly within the refined martensite lathes. In comparison with the tensile strength (1940 MPa) of general used steel (solution + aging treatment), the tensile strength of the sample processed by ECAP and subsequent aging treatment was enhanced for more than 100 MPa (above 2050 MPa). The enhancement of tensile properties was attributed to microstructural refinement and uniformly distributed nano-precipitates.

Microstructural Characterizations of Maraging Steel Processed by Equal-Channel Angular Pressing

“…The material preparation can be found in our previous work [6]. ECAP experiments were performed using a split die that could yield an effective strain of ~1 for a single pass [7], with two channels intersecting at inner angle of 90 o and outer angle of 30 o . The solidsolution rods in dimension of Φ16 mm × 80 mm lubricated with MoS 2 were processed through 1, 2, 4, 8, 12 and 16 passes (route B C [7]) at room temperature.…”

“…In our previous work [6][7][8], we reported that equal-channel angular pressing (ECAP) method was very effective in the refinement of the lath size, and lath width could be readily controlled during the multi-pass ECAP process. Accordingly, the yield strength of maraging steel was significantly enhanced by refining lath width down into nano-order via ECAP technique.…”