Aging reactions in 18-20%Ni maraging steels containing Co, Mo and Ti have been investigated. With Ti above about 1%, the formation of Mo rich zones is suppressed and the precipitation of phases containing Ti occurs. In an Fe-18%Ni-10%Co-5%Mo-2. 1%Ti alloy, the specific heat versus temperature curve is characterized by the appearance of three evolution peaks at 470, 540 and 600 degree C, corresponding to precipitation of a low temperature phase containing Ti,Ni//3Ti(DO//2//4) and Ni//3Mo. On isothermal aging at about 500 degree C, this alloy hardens by precipitation of the low temperature Ti-phase in the early stage and precipitation of Ni//3Mo in the later stage.
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