MECHANICAL STABILITY AND MAGNETIC-PROPERTIES OF AUSTENITE

Austenitic alloys have been produced by additional alloying in maragin g steel grade 18 Ni at 2400 MPa. The concentration of Mo, Ni and Co wa s increased individually until the martensite start temperature M(s), was suppressed below ambient value. Charpy impact strength, tensile st rength and magnetic properties were determined. The impact strength in the annealed condition ranged between 260 to 294 J. In alloys where m artensitic transformation occurred following quenching in liquid nitro gen, the impact strength dropped appreciably and was found to be in th e range 120-216 J. The tensile strengths of the austenite and martensi te phases ranged between 680 to 890 and 1030 to 1100 MPa. respectively . It was observed that the austenite phase transformed to martensite i n the region that under went plastic deformation during Charpy and ten sile testing. The degree of transformation incorporated, varied as a f unction of composition. The magnetic properties of the austenite phase s were typical of a very weak magnetic material. The coercive field an d saturation magnetization values were in the range 1034-2387 A m(-1) and 1.6-2.9 T, respectively. In contrast to the general observation, t he austenite phase containing high Co exhibited ferromagnetic behaviou r. The coercive field and saturation magnetization of ferromagnetic au stenite was 1034 A m(-1) and 11 T, respectively.