Twin-induced Grain Research Articles

The Recrystallization Nucleation Mechanism for a Low-Level Strained 316L Stainless Steel and Its Implication to Twin-Induced Grain Boundary Engineering

The Recrystallization Nucleation Mechanism for a Low-Level Strained 316L Stainless Steel and Its Implication to Twin-Induced Grain Boundary Engineering

Suppression of liquid-metal-embrittlement by twin-induced grain boundary engineering approach

Grain boundary engineering (GBE) has lately been recognized as a viable approach to manipulate grain boundary characteristics to improve resistance against intergranular degradation. One of the most challenging intergranular degradation phenomena is liquid-metal-embrittlement (LME), where a reactive liquid metal penetrates along random grain boundary network. In contrast to random grain boundaries, special coincidence site lattice (CSL) boundaries has been shown to be resistant against the embrittlement. The present study investigates the feasibility of using a GBE technique to arrest LME in a Fe (FCC)-Zn couple. Two sets of low-strain-heat-treatment processing routes were used to optimize grain boundary characteristics based on: (a) Σ3 and Σ3n boundaries frequency, and (b) the material's texture and grain size evolution. The optimum characteristics resulted in significantly improved resistance against LME. The mechanism of the embrittlement arrest is discussed based on the random-grain boundary network continuity and the grain boundary triple junctions distributione.

On the Strain-Hardening Behavior and Twin-Induced Grain Refinement of CP-Ti Under Ambient Temperature Compression

In this paper, a systematic investigation on the twin-induced grain fragmentation of commercially pure Titanium was carried out under quasi-static uniaxial compression test at ambient temperature. The compression tests were interrupted at various strain levels in order to examine the progressive evolution of the microstructure and texture. The detailed microstructural analysis was performed using the electron backscattered diffraction technique. The microstructural features indicated the presence of $$ \{ 10\bar{1}2\} $$ extension twins (ET), $$ \{ 11\bar{2}2\} $$ contraction twins (CT) and their interactions. The strain-hardening behavior of the material corroborates with the microstructural evidences. The strain-hardening rate and its derivative clearly distinguish the regions of slip- and twin-dominating zones with the increasing strain. The deformation texture substantiates that along with the twins, dislocation slips were active. The slip-based deformation finally deviates the twin boundaries from its special character at medium-to-high strains. At low strains, ET originate in texturally soft grains. These twin domains are comparatively texturally harder. They interact to form ET–ET with ~ 56.8 deg about $$ \langle 10\bar{1}0 \rangle $$ , with twin lamellar structure and consumes the entire parent grain with further deformation by twin expansion. CT develop on texturally hard grains with subsequent strains and were texturally softer. CT–CT, ET–CT-type twin interactions, and CT–ET double twins with ~ 77, ~ 87, and ~ 44.5 deg about $$\langle 10\bar{1}0 \rangle $$ , $$\langle 4\bar{2}\bar{2}1 \rangle $$ and $$\langle 5\bar{1}\bar{4}0 \rangle $$ axes, respectively, were observed. The microstructural changes corresponding to twin-boundary migration, interaction, and grain refinement are discussed on the basis of grain orientation spread and grain reference orientation deviation.

Improvement of the anti-corrosion property of twinning-induced plasticity steel by twin-induced grain boundary engineering

The effects of thermal-mechanical processing (TMP) on the microstructure and anti-corrosion property of twinning-induced plasticity (TWIP) steel are investigated. It is found that, the corrosion resistance of TWIP steel has been significantly improved with the corrosion potential increased from −0.92V to −0.69V and the corrosion current density reduced from 8.76×10−5A/cm2 to 1.92×10−5A/cm2. Electron back-scatter diffraction (EBSD) technique is employed to analyze the grain boundaries distributions of TWIP samples. The results indicate that the interrupted high angle boundaries network is the key to the improvement of the corrosion resistance of TWIP steel while the fraction of low-Σ coincidence site lattice boundaries is just slightly increased from 81% to 86%.

Improvement of Transpassive Intergranular Corrosion Resistance of 304 Austenitic Stainless Steel by Thermomechanical Processing for Twin-induced Grain Boundary Engineering

Grain boundary engineering (GBE) primarily aims to prevent the initiation and propagation of intergranular degradation along grain boundaries by frequent introduction of coincidence site lattice (CSL) boundaries into the grain boundary networks in materials. It has been reported that GBE is effective to prevent passive intergranular corrosion such as sensitization of austenitic stainless steels, but the effect of GBE on transpassive corrosion has not been clarified. In the present study, a twin-induced GBE utilizing optimized thermomechanical processing with small pre-strain and subsequent annealing was applied to introduce very high frequencies of CSL boundaries into type 304 austenitic stainless steels containing different phosphorus concentrations. The resulting steels showed much higher resistance to transpassive intergranular corrosion during the Coriou test, in comparison with the as-received ones. The high CSL frequency resulted in a very low percolation probability of random boundary networks in the over-threshold region and remarkable suppression of intergranular deterioration during GBE.

Twin-induced grain boundary engineering in 304 stainless steel

Grain boundary character distributions (GBCD) of type 304 stainless steel cold rolled and then annealed at 1173 K were analyzed by electron back scatter diffraction (EBSD). The results showed that low strain (6–10%) followed by long-time annealing (24–96 h) resulted in a GBCD containing a high fraction of ∑9 and ∑27 boundaries. The ratio of fraction summation of ∑9 and ∑27 boundaries ( f ∑9+∑27) to the fraction of ∑3 boundaries ( f ∑3), i.e. f ∑9+∑27/ f ∑3, reached 0.14 for the specimen strained by 6% and annealed at 1173 K for 96 h. The connectivity of general high angle grain boundary (HAB) network was interrupted significantly by ∑3 n ( n = 1–3) boundaries (special boundaries). However, intermediate strain (20–50%) followed by long-time annealing introduced a GBCD of a much lower fraction of ∑9 and ∑27 boundaries, the value of f ∑9+∑27/ f ∑3 was only around 0.03 and the connectivity of HAB network was not interrupted basically. Additionally, it was observed that a fair number of clusters consisting of ∑3–∑9–∑27 boundaries were developed in the process of low strain followed by long-time annealing (96 h), while the same phenomenon was hardly seen in the process of intermediate strain followed by long-time annealing.

Arrest of weld-decay in 304 austenitic stainless steel by twin-induced grain boundary engineering

A twin-induced grain boundary engineered 304 austenitic stainless steel with a high frequency of coincidence site lattice boundaries produced by a one-step thermomechanical process was arc-welded. The heat-affected zone was examined by orientation imaging microscopy and corrosion tests. The results indicated that the intergranular corrosion due to sensitization in the heat-affected zone were perfectly suppressed, because the high frequency of coincidence site lattice boundaries and the optimum grain boundary character distribution were stable in the grain boundary engineered stainless steel during arc-welding. The grain boundary engineering can arrest the weld-decay of austenitic stainless steel effectively.

Twin-induced grain boundary engineering for 316 austenitic stainless steel

By twin-induced grain boundary engineering utilizing optimized one-step thermomechanical processing with 3% pre-strain and subsequent annealing at 1240 K for 72 h, a very high frequency of coincidence site lattice (CSL) boundaries (86%) was introduced into type 316 austenitic stainless steel. The resulting steel showed a remarkably high resistance to intergranular corrosion during ferric sulfate–sulfuric acid tests. A CSL frequency of over 82% may result in a very low percolation probability of random boundary networks in per-threshold and a remarkable suppression of intergranular deterioration during twin-induced grain boundary engineering of austenitic stainless steels.

Suppression of chromium depletion by grain boundary structural change during twin-induced grain boundary engineering of 304 stainless steel

An analytical transmission electron microscopic study of a twin-induced grain boundary engineered 304 austenitic stainless steel demonstrated that the chromium depletion at a low-energy boundary segment introduced by twin-emission into a random boundary was smaller than that of the original random boundary after sensitization.

Optimization of grain boundary character distribution for intergranular corrosion resistant 304 stainless steel by twin-induced grain boundary engineering

The effects of process parameters, pre-strain, annealing temperature, time, etc. on grain boundary character distribution (GBCD) and intergranular corrosion in thermomechanical treatment were examined during grain boundary engineering of type 304 austenitic stainless steel. Slight pre-strain annealing at a relatively low temperature resulted in excellent intergranular corrosion resistance due to optimized GBCD, i.e. the uniform distribution of a high frequency of coincidence site lattice boundaries and consequent discontinuity of random boundary network in the material. The optimum distribution can be formed by introduction of low energy segments on migrating random boundaries during twin emission and boundary–boundary reactions in the grain growth without generation of new random boundaries.

Arrest of Intergranular Corrosion in Austenitic Stainless Steel by Twin-induced Grain Boundary Engineering(Student Poster Session)

Arrest of Intergranular Corrosion in Austenitic Stainless Steel by Twin-induced Grain Boundary Engineering(Student Poster Session)

Influence of cyclic thermal loading on brazed composites for fusion applications: Smid, I., Kny, E., Kneringer, G. and Reheis, N. J. Nucl. Mater. Apr. 1990 171, (1), 165–171

A twin-induced grain boundary engineered 304 austenitic stainless steel with a high frequency of coincidence site lattice boundaries produced by a one-step thermomechanical process was arc-welded. The heat-affected zone was examined by orientation imaging microscopy and corrosion tests. The results indicated that the intergranular corrosion due to sensitization in the heat-affected zone were perfectly suppressed, because the high frequency of coincidence site lattice boundaries and the optimum grain boundary character distribution were stable in the grain boundary engineered stainless steel during arc-welding. The grain boundary engineering can arrest the weld-decay of austenitic stainless steel effectively.

Recovery of edge-defined film-fed grown silicon Dislocation/twin boundary interaction and mechanisms for twin-induced grain boundary formation

Abstract Transmission electron microscopy and the electron-beam induced-current technique have been used to study changes in the defect structure of rapidly grown, edge-defined film-fed growth silicon ribbons, processed at high temperatures. Twin boundaries are the major structural defects in the ribbons, and these were found to act as strong obstacles to dislocation glide. This barrier eifect, possible mechanisms for slip transfer, and consequences for the mechanical and electrical properties of the silicon ribbons are discussed. Models are proposed to explain both twin-induced grain boundary formation during recovery of the microstructure and the generation of microtwins and second-order twin joins by glide-induced twinning processes.

Twin-induced grain boundary cracking in b.c.c. metals

Twin-induced grain boundary cracking in b.c.c. metals