Hierarchical evolution and thermal stability of microstructure with deformation twins in 316 stainless steel

Abstract

We report extensive nano-twin formation in 316 stainless steel (SS) and the evolution of a hierarchical microstructure through the formation of multi-scale twin bundles after uniaxial tension with uniform elongation levels of 20%, 30%, and 40%. Multiscale characterization techniques were employed to reveal the nature of these twins. The twin density increases with the increasing strain level, however, the twin width remains the same, notably reducing the mean free path of dislocations. Concurrently, significant work hardening is observed during subsequent deformation. The deformation-induced nano-twins are thermally stable up to ~800 ºC, shown by both interrupted and in-situ transmission electron microscopy experiments, above which the recrystallization takes place in the vicinity of the twins. Such favorable thermal stability of the twins in nano-twin strengthened 316 SS offers a promising approach for microstructurally engineering these materials for potential applications at elevated temperatures. The related strengthening mechanisms are discussed in the light of the mean free path of dislocations and the dislocation interactions with twin boundaries.

In vitro contact guidance of glioblastoma cells on metallic biomaterials

“…(2) The increase of SHR in stage II is possibly due to formation of deformation twinning [4,5]. In this stage prevention of cross slip can cause early onset of twinning, leading to further hardening of material [39]. In parallel with straining, grain size gets smaller as twins fragment the grains into smaller grains with different crystallographic orientations [9,49].…”

“…In order to eliminate topographical stimuli on cells, two sets of samples were prepared, where only one of them was polished post-mortem down to 1 μm with diamond abrasives (hereafter named as polished-samples) Then, these samples were etched at ambient temperature for 3 min in a solution of 10 ml nitric acid, 30 ml hydrochloric acid and 30 ml distilled water to reveal the activated mechanisms [39]. The microstructural evolution of the samples was observed via optical microscope (OM) in DIC mode and field-emission scanning electron microscope (SEM) with inlens SE (secondary electron) detector under an accelerating voltage of 10 kV.…”

Strain Hardening Behavior and Microstructure Evolution of High-Manganese Steel Subjected to Interrupted Tensile Tests

“…Secondary twins may be nucleated within the twins of the primary system [28]. Wang et al [29] observed the microstructure evolution in 316 stainless steel in a range of deformation levels: 10-30%. Deformation features evolved from planar dislocations to a single system twinning, then to multi-system twinning and intersections among twins, with increasing strain.…”

A Comparison of Strengthening Mechanisms of Austenitic Fe-13Mn-1.3C Steel in Warm and Cold High-Pressure Torsion

“…In this way, ultrafine-grained materials look very attractive due to superior strength properties but, having a high-volume fraction of intergranular boundaries, they simultaneously possess limited plasticity and thermal stability compared to coarse-grained counterparts [8,9,12]. GBE could be the possible way to make the ultrafine-grained materials more stable against recrystallization during post-deformation heat treatment, via producing of low-energy coherent special boundaries, for instance, twin-assisted Σ3 n boundaries [13][14][15][16]. For nanotwinned 330SS (stainless steel), Zhang and Misra [13] demonstrated a superior thermal stability of coherent twin boundaries, as microstructure of a Fe-22.3Mn-0.19Si-0.14Ni-0.27Cr-0.61C TWIP steel, due to formation of deformation microbands and twins during equal channel angular pressing at elevated temperatures (200 • C, 300 • C, and 400 • C) [32].…”