Effect of temperature and strain rate on strain hardening and deformation mechanisms of high manganese austenitic steels

Abstract

The effect of temperature and strain rate on the mechanical properties of three Fe – Mn austenitic steels with Mn contents of 20 mass.% or above has been studied by tensile tests performed at strain rates ranging from 3 × 10−3 to 200s−1 and at temperatures between −160 and +140 °C. In these steels mechanical properties and strain hardening behaviour result from the competition between different deformation mechanisms including homogeneous or inhomogeneous dislocation glide, strain induced twinning or martensite formation. Thus, the microstructure evolution during deformation was investigated. For two of the steels, a relation of the deformation mechanisms (twinning and dislocation glide) at room temperature with the grain size was found. On the other hand, for the third steel at temperatures lower than 60 °C martensite is progressively formed during deformation. For the three steels, a decreasing volume fraction of twins or martensite with increasing testing temperature was found leading consequently to a decrease in flow stress and strain hardening.

Fatigue behavior of Ti6Al4V and 316 LVM blasted with ceramic particles of interest for medical devices

“…Such values contrast with the higher values determined for cp Ti (about 0.5) (Boller and Seeger, 1987) and 316L alloy (about 0.41) (Byun et al, 2001). The high levels of strain hardening in these alloys have been associated to the development of mechanical twinning during deformation (Bäumer et al, 2010).…”

“…6a). This result has been associated in other austenitic steels to the formation of mechanical twinning (TWIP-effect) during deformation (Bäumer et al, 2010). As the volume fraction of twins increases with strain, the mean free path of dislocations decreases rapidly, causing high levels of strain hardening in the material.…”

Ab Initio-Based Modelling of the Yield Strength in High-Manganese Steels

“…Generally speaking, the effect of temperature changes on the lattice parameter and on intrinsic material properties that derive from electron effects like electrical conductivity is often approximated to be linear [44]. The serrated flow curves of many high-manganese TWIP steels usually occur at temperatures of up to about 200 • C. At higher temperatures, this dynamic strain aging-like effect is either very small or is not detected at all [2,7].…”

“…Those deformation modes include transformation induced plasticity (TRIP), twinning-induced plasticity (TWIP) or pronounced planar glide in combination with the formation of dislocation cells that is sometimes referred to as microband-induced plasticity (MBIP) [1,[8][9][10]. The mode of deformation significantly influences the level of work hardening and plays a major role in determining the mechanical properties [7]. One of those material characteristics is the material's yield strength (YS).…”

“…Depending on the stacking fault energy, which is a result of alloying content, temperature, deformation grade, and other factors, HMnS exhibit a variety of different active deformation modes [4][5][6][7]. Those deformation modes include transformation induced plasticity (TRIP), twinning-induced plasticity (TWIP) or pronounced planar glide in combination with the formation of dislocation cells that is sometimes referred to as microband-induced plasticity (MBIP) [1,[8][9][10].…”