Characterization of cold-rolled and aged MP35N alloys

Systematic research has been undertaken on the effects of deformation and aging on the mechanical properties and microstructures of MP35N alloys. A relationship among the aging time, aging temperatures and mechanical properties has been established and the optimum aging conditions were critically assessed by evaluation of the variations of hardness with the thermal processing conditions. Aging of 65% cold-rolled MP35N alloys at 550 °C for 8 h produced materials with hardness values of 5647±78 MPa (580 HV) and yield strength of 2125 MPa at room temperature. At −196 °C, the yield strength reached 2511±1 MPa and the work hardening rate was higher than that at room temperature. Assisted by electropolishing, light microscopy and scanning electron microscopy (SEM) revealed the microstructure changes in the materials, whereas the detailed microstructure introduced by cold deformation and aging was studied by transmission electron microscopy (TEM). Deformation results in production of {110}〈1̄12〉 and {110}〈1̄11〉 textures, rotation of the annealing twin boundaries and introduction of very fine platelets that strengthen the face-centered-cubic (fcc) matrix.