Fracture behaviour of duplex stainless steel was analyzed arising from temperature dependencies of strength properties, fracture toughness, impact energy and, in particular, from characteristics of load - deflection traces obtained using instrumented impact tester. At uniaxial tensile loading, the ferrite transition behaviour is significantly compensated by austenite plasticity. Fracture of Charpy V-notch specimens and precracked compact tension specimens, respectively, in transition and lower shelf regions is controlled by fracture behaviour of ferritic constituent of the microstructure. Critical (effective) fracture stress at the onset of unstable fracture for Charpy type specimen was estimated. The values determined are well comparable with results of FEM calculation.
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