Low-temperature deformation mechanisms in an Fe-Si-Ti alloy

Abstract

The temperature and strain-rate dependence of the yield and flow stresses of an age-hardened Fe-Si-Ti alloy, and a binary Fe-Si alloy, have been investigated in the temperature range 77 to 330 K. The parameters of activated deformation have been determined as a function of the precipitate dispersion and it is concluded that these parameters are unaffected by precipitation even when particles are sheared by dislocations, implying that bcc iron alloys cannot be dispersion strengthened at room temperature without making them even stronger, and hence more brittle, at lower temperatures. Work-hardening of all alloys is due to increases in the athermal component of the applied stress. The activation enthalpy at low effective stresses is larger than that for pure iron, indicating that silicon exerts a higher lattice friction stress due to its effect on the core asymmetry of screw dislocations in iron.