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Keywords:

  • strain rate sensitivity;
  • pre-straining;
  • adiabatic heating;
  • dynamic tensile testing;
  • metastable austenitic stainless steel

Abstract

The dynamic behavior of AISI 301LN2B (EN 1.4318) metastable austenitic steel grade has been investigated at 296 K by means of servohydraulic tensile and split Hopkinson bar testing in the strain rate range 0.005–1000 s−1. As delivered, as well as 10% uniaxial, biaxial, and plane strain pre-strained conditions, without subsequent heat treatment have been tested. A negative strain rate sensitivity is observed in the low strain rate range between 10−4 and 1–10 s−1. Pre-straining reduces the magnitude of the adiabatic tensile strength softening, especially in the plane strain condition with higher triaxility. The thermal activation related dynamic flow stress increase is not dependent on pre-straining. The γ [RIGHTWARDS ARROW] α′ induced additional flow stress increase, however, is highly strain rate and pre-straining sensitive. The amount of pre-straining determines the overall ductility at fracture, and therefore the adiabatic temperature increase. The pre-straining stress state influences the amount of α′-martensite formed before dynamic testing, and consequently the maximum intensity of the TRIP induced flow stress increase by subsequent dynamic testing.