Finite element method simulation of the hot extrusion of a powder metallurgy stainless steel grade
Oxides Dispersed strengthened (ODS) stainless steels are foreseen for fuel cladding tubes in the coming generation of fission nuclear reactors. In spite of a ferritic matrix those steels present a convenient creep behavior thanks to very fine oxides dispersion. Those grades are currently obtained by Powder Metallurgy (PM). After mechanical alloying with the oxide, the powder is commonly consolidated by Hot Isostatic Pressing (HIP) or Hot Extrusion (HE). The control of microstructure after extrusion is a key issue for this grade regarding service conditions. On CEA facilities, new ferritic ODS stainless steels are produced by HE. In order to explain the microstructure observed at various places on an interrupted extrusion samples the thermo-mechanical history applied to the material must be determined. In this paper we use the Finite Element Method to simulate the co-extrusion of a PM grade in a soft steel can. The PM steel grade behavior law is determined on a fully dense material by hot torsion tests, taking into account temperature and strain-rate sensitivity. Thus strain and thermal history are computed for material points lying on various flow lines during extrusion.
finite element method hot extrusion powder metallurgy numerical modeling oxides dispersed strengthened steel