Kink Band Boundaries Research Articles

Transformational faulting in Mn2GeO4 from olivine to wadsleyite structure: Implications for physical mechanism of deep-focus earthquakes

High-pressure and temperature deformation experiments interfaced with acoustic emission (AE) monitoring have been conducted to study transformational faulting in Mn2GeO4 olivine, which transforms to the β phase, isostructural to wadsleyite. Metastable Mn2GeO4 olivine exhibits a marked embrittlement behavior at temperatures between 800 and 1100 K, emitting numerous AEs. At each temperature, brittle deformation is characterized by a two-stage process: (1) a “preparation” stage with numerous diffusedly located low-magnitude AEs and large b values (>2), and (2) a failure stage where larger-magnitude AEs form a planar distribution with b values about 1. Microstructure analysis reveals extensive kink band development in olivine grains in the recovered samples. Kink band boundaries (KBBs), with a typical thickness of ∼100 nm, are filled with a nanometric β-Mn2GeO4 “gouge”. A dense array of secondary shear localizations is often present within the kink bands, suggesting significant shear deformation therein. The combined observations suggest that faulting in metastable Mn2GeO4 olivine is a self-similar process, from grain-scale to the sample-scale. Both observed embrittlement behavior and the microstructure of metastable Mn2GeO4 olivine are essentially identical to those in Mg2GeO4 olivine we have reported previously, indicating that the physical mechanism of faulting in metastable olivine is insensitive to the specific crystallographic structure of the high-pressure phase. The low b values (about 1) observed in the faulting process in our experiments are similar to those of deep focus earthquakes in cold subduction zones. Our observed mechanism explains deep focus seismicity in cold metastable mantle wedges, provided that the self-similarity assumption holds to geological scales.

Effect of long-period stacking ordered phase on dynamic recrystallization in Mg-Y-Zn-Zr alloy processed by backward extrusion

During the backward extrusion process, the impact of the long-period stacking ordered (LPSO) phase on dynamic recrystallization (DRX) in the Mg-10Y-2Zn-0.5Zr alloy was studied. The results show that DRX at the α-Mg/18R-LPSO interface belongs to the discontinuous dynamic recrystallization (DDRX) mechanism, and the DRX at the α-Mg/14H-LPSO interface belongs to the continuous dynamic recrystallization (CDRX) mechanism. Under the action of strain force, the 18R-LPSO interface migrates locally to form a “convex” structure. It was easy to produce high-density dislocations around the structure, which promoted DDRX at the α-Mg/18R-LPSO interface. The lamellar 14H-LPSO would undergo severe kink and form a large number of kink bands, providing favorable nucleation sites for CDRX grains. With the increase of the extrusion strain force, the lamellar 14H-LPSO kink angle gradually increases, which promotes the nucleation of CDRX grains at the kink band boundary. In addition, the production of 14H-LPSO kink activates prismatic <a>slip, pyramidal <a>slip and pyramidal <c+a>slip in the α-Mg matrix.

The effect of annealing on kink band formation in Ag/Fe nanolaminates

Kink banding is a common, though not well understood, failure mechanism in anisotropic materials such as nano metallic laminates (NMLs). In this work, we investigate the effect of annealing on kink band (KB) formation in Ag/Fe NMLs prepared by accumulative roll bonding (ARB) using in situ micropillar compression, scanning/transmission electron microscopy (S/TEM), and transmission Kikuchi diffraction (TKD) analyses. Our results show that annealing increases the KB initiation strain, decreases the probability of KB formation, and decreases the load drop magnitude accompanying kink banding in Ag/Fe NMLs. Post-compression analyses reveal that annealing facilitates more uniform deformation of pillars and affects the formation of geometrically necessary grain boundaries (GNBs) near the kink band boundary (KBB). Compared to its as-rolled counterpart, annealed Ag/Fe has wider KBs with blunter KBBs.

The microstructure evolution and tensile properties of Ti–43Al–4Nb–1Mo-0.2B alloy during hot rolling

Ti–43Al–4Nb–1Mo-0.2B (at.%) (TNM) alloy sheets were fabricated, and the corresponding microstructure developed from lamellar to duplex structure with the rolling reduction increased from 50% to 72.5%. Interestingly, a novel Z-type lamellar structure developed at 67.5% deformation strain, and the formation process was discussed by calculating the Schmid factor. Moreover, α2+γ→βo phase transformation occurred at the kink band boundaries. Subsequently, as the reduction increased to 72.5%, the coarse βo phase decomposed and transformed to α2+γ phases due to the distortion energy stored after multi-pass rolling. Finally, the room-temperature tensile properties of the TNM sheets were tested. With the comparison of the as-forged alloy, the strength and ductility increased significantly by hot rolling, and the ultimate tensile strength reached 880 MPa at 60% total reduction. The relationship between the rolling process, microstructure evolution, and corresponding properties was established.

Kink mechanism in Cu/Nb nanolaminates explored by in situ pillar compression

Nano metallic laminates (NMLs) exhibit different failure modes depending on the loading conditions due to their mechanical anisotropies. Kinking is a typical failure mode in many NMLs compressed along a layer-parallel direction. However, a detailed description of the microstructure evolution during kink band (KB) formation and an in-depth understanding of the formation mechanisms are lacking. In this work, the KB process is investigated in Cu/Nb NMLs by in situ micro pillar compression in the scanning electron microscope (SEM) along a layer-parallel direction. Post-mortem S/TEM and transmission Kikuchi diffraction (TKD) analyses show that kink banding leads to significant microstructure changes characterized by an accumulation of geometrically necessary dislocations (GNDs) and of tilt geometrically necessary boundaries (GNBs) near KB boundaries (KBBs). The distinct microstructure evolution implies that KB formation is facilitated by the inhomogeneous microstructures resulting in constrained deformation modes. Specifically, dislocations active on slip planes nearly parallel to the interfaces make a major contribution to kink evolution after the onset of kinking. Once layer-parallel slip systems are activated, preexisting lattice dislocations and dislocations nucleating from interfaces will accumulate as GNDs near KBBs via the stochastic storage of lattice dislocations that have certain Burgers vectors. GNDs can further transform into GNBs via cross-slip and climb driven processes near the KBB. Furthermore, GNBs near KBBs can grow by incorporating more GNDs or by coalescence to accommodate the KB evolution. We further hypothesize that microstructural perturbations and their ensuing stresses can initiate KB formation in Cu/Nb NMLs.

Crystallographic features of &lt;11¯00&gt; axis tilt boundaries in a high strain rate deformed Mg 9Y alloy

In this study, the microstructure evolution of solution-treated Mg9Y alloy during high strain rate deformation was systematically investigated. Abundant deformation bands were formed to subdivide the grain. The crystallographic features of these defomation bands, including the {112¯1} twin, twin-like tilt boundaries, {112¯2} twin and kink bands, were identified by characteristic misorientation angles along <11¯00> axis. The {112¯2} twin was observed for the first time in Mg alloys, and probably evolved from {112¯1} twin through lattice rotation along <11¯00> axis in this case. To accommodate strain in a short time, kink band boundaries with <11¯00> rotation axis were formed due to local lattice rotation and interacted with {112¯1} twin boundaries, resulting in the the formation of <11¯00> axis tilt boundaries with various misorientation angles. The lattice rotation process was attributed to the basal <a > and pyramidal-II < c + a > dislocation slips under high strain rate deformation. These results will offer insight into microstructure evolution during high strain rate deformation and inspire the development of high-performance Mg alloys.

Evolution of fibre deflection leading to kink-band formation in unidirectional glass fibre/epoxy composite under axial compression

We present the first experimental observation and quantification of the evolution of the three-dimensional (3D) deflection of fibres leading up to kink-band formation in notched unidirectional glass fibre-epoxy composites. This has been achieved by in situ synchrotron X-ray computed tomography (CT) quantified by advanced image analysis. The 3D trajectories of individual fibres were extracted to monitor the change in fibre profiles with increasing compressive load. Initially the fibre trajectory varies significantly from fibre to fibre, the waviness of which cannot be represented by a simple idealised profile. However, the change in the fibre shapes during axial compression is similar for all fibres, as the fibres deflect towards the final kinking direction. The precursor to kink-band nucleation has been identified as a local tilting of fibres in the region where the kink bands ultimately form, defining a micro-buckle band. Even at 99.9% of the failure load this micro-buckle band is much narrower (~150 μm (~12 fibre diameters) wide), and the angle of inclination of the band much shallower (~8°), compared to the final 300–400 μm (25–33 fibre diameters) wide, and 25–30° inclined, kink band. It is notable that kink-band boundaries are delineated by fibre fractures, many of which exhibit wedge-shaped multiple fractures.

Deformation at low and high stress-loading rates

In an extensional shear zone in the Talea Ori, Crete, quartz veins occur in high-pressure low-temperature metamorphic sediments at sites of dilation along shear band boundaries, kink band boundaries and boudin necks. Bent elongate grains grown epitactically from the host rock with abundant fluid inclusion trails parallel to the vein wall indicate vein formation by crack-seal increments during dissolution-precipitation creep of the host rock. The presence of sutured high-angle grain boundaries and subgrains shows that temperatures were sufficiently high for recovery and strain-induced grain boundary migration, i.e. higher than 300–350 °C, close to peak metamorphic conditions. The generally low amount of strain accumulated by dislocation creep in quartz of the host rock and most veins indicates low bulk stress conditions of a few tens of MPa on a long term. The time scale of stress-loading to cause cyclic cracking and sealing is assumed to be lower than the Maxwell relaxation time of the metasediments undergoing dissolution-precipitation creep at high strain rates (10−10 s−1 to 10−9 s−1), which is on the order of hundred years. In contrast, some veins discordant or concordant to the foliation show heterogeneous quartz microstructures with micro-shear zones, sub-basal deformation lamellae, short-wavelength undulatory extinction and recrystallized grains restricted to high strain zones. These microstructures indicate dislocation glide-controlled crystal-plastic deformation (low-temperature plasticity) at transient high stresses of a few hundred MPa with subsequent recovery and strain-induced grain boundary migration at relaxing stresses and temperatures of at least 300–350 °C. High differential stresses in rocks at greenschist-facies conditions that relieve stress by creep on the long term, requires fast stress-loading rates, presumably by seismic activity in the overlying upper crust. The time scale for stress loading is controlled by the duration of the slip event along a fault, i.e. a few seconds to minutes. This study demonstrates that microstructures can distinguish between deformation at internal low stress-loading rates (to tens of MPa on a time scale of hundred years) and high (coseismic) stress-loading rates to a few hundred MPa on a time scale of minutes.

Strain-rate dependence of deformation behavior of LPSO-phases

This is the first report clarifying the influence of the strain rate on the deformation behavior of Mg-based long-period stacking ordered (LPSO) phases with 14H, 18R, and 10H structures. The flow stress by basal slip showed a weakly positive or negligible strain-rate dependence, while the flow stress accompanied by the formation of deformation kink bands showed a unique negative strain-rate dependence. These results give the first experimental evidence on the recent proposal that Zn and Y atoms segregate at the kink band boundaries and hinder their migration, from the viewpoint of the mechanical properties.

X-ray computed tomography study of kink bands in unidirectional composites

An experimental study on the axial compressive failure of cylindrical unidirectional (UD) carbon fibre-epoxy rods has been performed to better understand kink bands and the relevant damage mechanisms in three dimensions (3D). Post-mortem X-ray micro-computed tomography (micro-CT) imaging has shown that fibre kink bands predominantly all lie within the same plane in a cylindrical rod sample uniaxially compressed without lateral constraint. Kink bands at different stages of development are contained in the damage volume and the geometric parameters of fully developed kink bands are consistent through the damage zone, with a kink-band width ω≈20–320 μm, kink-band angle β≈11–40° and fibre rotation angle Φ (φ+φo)≈18–52°. Fibre failure, longitudinal splitting and matrix micro-cracks within the fibre kink zone are identified by scanning electron microscopy (SEM) and X-ray micro-CT observations. The smallest radius of curvature that corresponds to maximum amount of bending of the unbroken buckled fibres was ∼280μm (40 fibre diameters). Kink-band boundary planes and longitudinal splitting have been extracted and visualised in 3D for the first time.

Formation of [formula omitted] twin boundaries in titanium by kinking mechanism through accumulative dislocation slip

The twinning behavior and kinking behavior of a commercial purity Ti subjected to room temperature dynamic plastic deformation (DPD) has been studied. Three types of deformation twins, {101¯2}, {112¯2} and {112¯1}, have been observed. It is found that a considerable fraction of the {112¯1} twin crystals were encompassed by the twin boundary segments in connection with kink band boundaries with much lower misorientation angles. A close investigation on the crystallographic nature of these deformation twins revealed that the {112¯1} twin boundaries have evolved from deformation kink band boundaries through accumulative slip of single basal-〈a〉 dislocations. This mechanism for the formation of twin boundaries is different from the known mechanisms through deformation twinning in metals, for which the twin orientation relationship has been achieved once the twin embryo is nucleated. The mechanism for the formation of kink band, the transformation from kink band boundary to deformation twin boundary and the further evolution of twin boundaries during DPD have been discussed in terms of Schmid factors of various dislocation slip systems.

Electron backscatter diffraction pattern analysis of the deformation band formed in the Mg-based long-period stacking ordered phase

A newly proposed analysis protocol using electron backscatter diffraction pattern analysis in scanning electron microscopy (SEM-EBSD) clarified that the deformation bands formed in the Mg-based long-period stacking ordered (LPSO) phase are predominantly deformation kink bands. The kink band contains many additional boundaries within it, and the coalescence of these boundaries varies the crystal rotation angle and rotation axis at the kink band boundaries during their development. The reason for the appearance of a “beak-like” shape in deformation kink band in the LPSO phase was clarified by proposing a unique three-dimensional morphology.

The deformation record of olivine in mylonitic peridotites from the Finero Complex, Ivrea Zone: Separate deformation cycles during exhumation

AbstractMylonitic peridotites from the Finero complex are investigated to detect characteristic olivine microfabrics that can resolve separate deformation cycles at different metamorphic conditions. The heterogeneous olivine microstructures are characterized by deformed porphyroclasts surrounded by varying amounts of recrystallized grains. A well‐developed but only locally preserved foam structure is present in recrystallized grain aggregates. This indicates an early stage of dynamic recrystallization and subsequent recovery and recrystallization at quasi‐static stress conditions, where the strain energy was reduced such that a reduction in surface energy controlled grain boundary migration. Ultramylonites record a renewed stage of localized deformation and recrystallization by a second generation of recrystallized grains that do not show a foam structure. This second generation of recrystallized grains as well as sutured grain and kink band boundaries of porphyroclasts indicate that these microstructures developed during a stage of localized deformation after development of the foam structure. The heterogeneity of the microfabrics is interpreted to represent several (at least two) cycles of localized deformation separated by a marked hiatus with quasi‐static recrystallization and recovery and eventually grain growth. The second deformation cycle did not only result in reactivation of preexisting shear zones but instead also locally affected the host rock that was not deformed in the first stage. Such stress cycles can result from sudden increases in differential stress imposed by seismic events, i.e., high stress‐loading rates, during exhumation of the Finero complex.

Orientation dependence of the deformation kink band formation behavior in Zn single crystal

Variations in deformation kink band formation behavior with loading orientation were examined by the combination of experiment and computer simulation, using the Zn single crystal as a model material. Based on the results, the controlling factors for the formation behavior of deformation kink bands and its general features were discussed. Due to compression parallel to the basal plane, several deformation bands formed in the Zn single crystal. By the examination of the crystallographic nature of the deformation bands, they were found to exhibit three characteristic features: an ambiguous crystal rotation axis on the [0001] zone axis, an arbitrary rotation angle with a wide variation, and a variation in the crystal rotation angle within the deformation band boundary itself. In addition, an analysis protocol to classify the nature of the deformation bands via the observation on (0001) was newly proposed. As a result, the deformation bands formed in the Zn single crystal were confirmed to be predominantly deformation kink bands rather than deformation twining.Among the abovementioned three crystallographic features, we first experimentally confirmed by using the single crystal that the variations in the rotation axis in deformation kink bands exhibit a strong dependence on loading orientation. Using computer simulation based on the crystal plasticity finite element analysis, the origin of the variation in rotation axis in deformation kink bands was clarified to be due to the initiation of different types of basal dislocations that construct the deformation kink band boundaries, which depends on the loading orientation. In addition, the variations in types of the dislocations owing to the internal stress were found to cause the significant waviness of the deformation band boundaries on (0001) specimen surface.

청산화강암의 압쇄암화작용 동안에 미구조 변화

거정 장석반정을 다량 함유하는 청산화강암이 연성전단변형을 받아 압쇄암화되는 동안에 일어난 미구조 변화를 파악하기 위해 변형된 청산화강암의 암석구조와 미구조 연구를 수행하였다. K-장석에서 특징적인 미구조는 미세킹크, 미세단열, 밀메카이트, 플레임 퍼어사이트, 코아 외부에 아입자 발달이 없는 코아-맨틀구조 등으로 인지된다. 미세킹크는 미세 단열되거나 미단열된 K-장석들에서 모두 관찰되고, 미세킹크의 축 방향은 미세단열에 의해 경계져 있는 양쪽 K-장석으로 연장된다. 밀메카이트와 플레임 퍼어사이트는 미세 단열된 K-장석들의 입계에 고 변형량의 집중으로 발달한다. 사장석에는 미세단열, 변형쌍정, 킹크대 등이 우세하게 관찰된다. 거정 사장석 반정의 입도 세립화는 역시 미세단열작용에 의해 진행되었다. 그러나 미세 단열된 K-장석과 달리 미세 단열된 사장석에는 코아-맨틀구조가 관찰되지 않는다. 화성기원의 누대구조를 중첩하는 변형쌍정은 변형정도가 낮은 저 변형암에서 종종 관찰된다. 고 변형암에서 변형쌍정의 엽층들은 일반적으로 공액성 킹크대의 둔각 이등분선 방향으로 발달하고, 미세단열 내지 미세단층 되어 무질서한 배열을 보인다. 따라서 이와 같은 특징적인 미구조로부터 청산화강암의 압쇄암화작용 동안에 미구조는 다음과 같이 발달하였음을 제시한다: 거정 K-장석 반정에 미세킹크의 출현과 사장석에 킹크대와 변형쌍정의 출현, 미세단열작용에 의한 거정 장석반정들의 입도 세립화, 미세 단열된 K-장석에 밀메카이트와 플레임 퍼어사이트 그리고 입계이동 재결정작용에 의한 K-장석 조각들의 입도 세립화와 함께 코아-맨틀구조의 출현. Rock structural and microstructural analyses on the deformed Cheongsan granite, which is characterized by abundant feldspar megacrystals, have been carried out to understand the microstructural change during the mylonitization by ductile shear deformation. In K-feldspars, the characteristic microstructures are recognized as microkinks, microfractures, myrmekites, flame perthites, and core-and-mantle structures without the development of subgrains in outer core-zone. Microkinks are observed in both the microfractured and unmicrofractured K-feldspars and the directions of their axes are generally extended across the adjacent K-feldspar fragments bounded by microfractures. Myrmekites and flame perthites are found on the strain-localized boundaries of the microfractured K-feldspars. In plagiclases, microfractures, deformation twins and kink bands are predominant. Grain size reduction of plagioclase megacrysts also occurs by microfracturing but the core-and-mantle structures like the case of K-feldspars are uncommon in the microfractured plagioclases. The deformation twins, which overlap the igneous zoning structures, are often found in less deformed rocks. The twin lamellae in more deformed rocks generally bisect the obtuse angles of conjugate kink-band boundaries, and are microfractured or microfaulted and randomly oriented. From such characteristic microstructures, thus, it can be suggested that the micostructures during the mylonitzation of Cheongsan granite was developed as follows: production of microkinks in the K-feldspar megacrysts and of deformation twins and kink bands in the plagioclase megacrysts, and then grain-size reduction of the feldspar megacrysts through microfracturing, and then production of core-and-mantle structures (grain-size reduction of the microfractured K-feldspars through grain boundary migration), myrmekites and flame perthites in the microfractured K-feldspars.

Contractional kink bands formed by stress deflection along pre-existing anisotropies? Examples from the Anglo-Brabant Deformation Belt (Belgium) and the North Dobrogea Orogen (Romania)

Kink bands within two slate belts, the Anglo-Brabant Deformation Belt (Belgium) and the North Dobrogea Orogen (Romania), reveal similar problems with respect to linking kink band geometries to expected palaeostress directions. In the North Dobrogea Orogen, the two opposite kink band sets of two different systems of conjugate kink bands develop for a wide variety of cleavage orientations. In the Anglo-Brabant Deformation Belt, the occurrence of the two opposite kink band sets of a conjugate kink band system opposes the expected occurrence. In both cases, this can be attributed to stress deflection along a pre-existing anisotropy. Moreover, the presence of kink bands in the North Dobrogea Orogen with curving kink axes (and curving kink band boundaries) also puts doubt on the direct relationship between kink band geometry and stress. The idea of stress deflection along a pre-existing anisotropy and the strong control of the pre-existing anisotropy on the kink band geometry and orientation has important implications for the use of kink bands as regional palaeostress indicators. Depending on the relative intensity and relative orientation of the pre-existing fabrics (here bedding and cleavage), different mechanisms of kink band development may operate. Depending on the mechanism, different solutions in terms of inferred palaeostress direction may exist.

Relationships between the microstructural evolution and the rheology of talc at elevated pressures and temperatures

We conducted triaxial compression experiments to investigate the effects of pressure, temperature and strain rate on the rheology of talc rocks. The tests were carried out at T from 25 to 860 °C, P from 0.1 to 300 MPa, and ε˙ from 0.3 to 30 × 10 − 5 s − 1 . In addition to being very weak, there are other important differences between the mechanical behavior of talc and that of most other silicates. Deformation at all temperatures up to dehydration was accommodated by a combination of crystal plasticity, frictional sliding, and cataclasis. A transition from localized to distributed deformation occurred at P = 300 MPa and T = 400 °C, but this transition is ill-defined as both distributed and localized deformation were observed at P = 300 MPa and T = 600 °C. Unlike most silicates, both the coefficient of internal friction and the coefficient of (sliding) friction are very low and nearly equal to each other. Temperature enhances plastic deformation (kinking), and inter- and intra-granular microcracks are observed parallel to the (001) planes at all conditions. Voids are created by delamination along (001) planes at kink-band boundaries. Full crystal plasticity was not achieved under any of the conditions tested, i.e., the von Mises criterion was never satisfied. However, the strength of the aggregates remained much less than the confining pressure. These unusual properties are likely a manifestation of the pronounced mechanical anisotropy of talc at the grain scale. At T ≥ 750 °C dehydration is observed, but only along shear zones. These results suggest that feedbacks between deformation and reaction kinetics could control fluid flow in fault zones. The presence of talc can promote significant weakening and strain localization in the oceanic lithosphere, the subducting plate and the overlying mantle wedge.

Tensile deformation and fracture behaviors of high purity polycrystalline zinc

The damage and fracture behaviors of high purity polycrystalline zinc with two grain sizes during tension were investigated experimentally at different strain rates. It was found that specimens with coarse grains (∼1 mm) showed serrated flow behavior and failed in intermittent brittle cleavage fracture, while specimens with fine grains (∼70 μm) showed no cleavage crack initiation before necking even at high strain rate. It was observed that the fracture process of the fine-grained specimen was highly related to strain rates. With the strain rate increasing, the damage mechanism transformed from formation of tearing cracks along interfaces (including grain boundaries, twin boundaries and kink band boundaries) and cavity coalescence into abrupt quasi-cleavage fracture. Based on the observation, the inter-crystalline fracture of zinc was investigated, and the damage and fracture behaviors of polycrystalline zinc during tension at room temperature were discussed in general.

Kink bands in the Chamba region, Western Himalaya, India

The Chamba region of the western Himalaya is affected by three phases of deformation (DF 1, DF 2, and DF 3). The DF 1 phase was the most intense and regionally extensive as expressed by the development of the Chamba-Bhramaur syncline. The kink bands developed on the limbs of the syncline during the third (DF 3) phase of deformation on S 1 fabric. The kink bands are of contractional type and well developed in the slate-phyllite sequence of the Salooni and Pukhri Formations. The palaeostress analysis from conjugate kink bands indicates that the maximum compressive stress ( σ 1) was oriented N50°E–S50°W in present coordinates, which nearly coincides with the maximum compressive direction inferred from DF 1 (First phase) and DF 2 (second phase) deformation. The geometry, angular relationship between the kink band boundary and the external cleavage ( α) and the internal angle of the kink band ( β) and strain in kink bands reveal that rotation and dilation was the dominant mechanism. The morphology, kinematics and dynamics of the kink bands suggest that they formed towards the end of the last phase of deformation during emplacement of the Chamba nappe without metamorphism.

Evolution of Kink Bands and Tilt Boundaries in Block Copolymers at Large Shear Strains

The evolution of kink bands and kink band boundaries in a prealigned poly(styrene-b-ethylene propylene) lamellar diblock copolymer was investigated by applying steady shear at strains in the range of 1−10 strain units. Boundary morphologies were characterized using transmission electron microscopy. As the shear strain increases, both the kink bands and the lamellae within the kink bands rotate continuously toward the shearing direction, leading to a decrease in the tilt boundary angle and the kink band boundary angle. Simultaneously, the nature of the kink band boundary transforms. The chevron boundaries present at low strains, and thus large tilt angles, become omega boundaries as the strain increases to ∼3 strain units. At higher strains (∼5 strain units), the tilt angle further decreases, and the omega boundaries start to break, preferentially in the PS microdomains. Delamination of the PS microdomains was also observed at the highest strain amplitude (10 strain units), which was associated with the limited extent of entanglement across the PS microdomains.