Early stages of surface relief evolution of persistent slip markings (PSMs), formed in areas where persistent slip bands (PSBs) intersect the free surface, in polycrystalline 316L stainless steel cycled with constant plastic strain amplitude were studied using atomic force microscopy (AFM) and electron backscattering diffraction (EBSD). Focused ion beam (FIB) technique was employed to obtain additional, more detailed information on the shape of PSMs. To reveal true qualitative and quantitative information on the simultaneous growth of intrusions and extrusions within individual PSMs, identical areas both on the specimen surface and on its inverse copy obtained via plastic replica were studied using AFM. Intrusions are preceded by extrusions regardless of orientation of individual grains of the polycrystal. The first intrusions appear largely around 1% of fatigue life at the moment when ‘static’ extrusions are developed. They appear predominantly but not exclusively at the side of extrusions where the emerging active slip plane is inclined to the surface at an acute angle. They grow faster than the stage of stable extrusion growth. Typical morphology of mature PSMs developed at 15% of fatigue life consists of ribbon-like extrusions accompanied by two thin parallel intrusions along both PSB–matrix interfaces. Experimental data on the morphology and growth of extrusions and intrusions are discussed in relation to the theoretical models and computer simulations of surface relief evolution leading to fatigue crack initiation.

The interest in understanding scaling limits of magnetic textures such as domain walls spans the entire field of magnetism from its physical fundamentals to applications in information technologies. Here, we explore antiferromagnetic CuMnAs in which imaging by x-ray photoemission reveals the presence of magnetic textures down to nanoscale, reaching the detection limit of this established microscopy in antiferromagnets. We achieve atomic resolution by using differential phase-contrast imaging within aberration-corrected scanning transmission electron microscopy. We identify abrupt domain walls in the antiferromagnetic film corresponding to the Néel order reversal between two neighboring atomic planes. Our work stimulates research of magnetic textures at the ultimate atomic scale and sheds light on electrical and ultrafast optical antiferromagnetic devices with magnetic field–insensitive neuromorphic functionalities.

Efficient manipulation of antiferromagnetic (AF) domains and domain walls has opened up new avenues of research towards ultrafast, high-density spintronic devices. AF domain structures are known to be sensitive to magnetoelastic effects, but the microscopic interplay of crystalline defects, strain and magnetic ordering remains largely unknown. Here, we reveal, using photoemission electron microscopy combined with scanning X-ray diffraction imaging and micromagnetic simulations, that the AF domain structure in CuMnAs thin films is dominated by nanoscale structural twin defects. We demonstrate that microtwin defects, which develop across the entire thickness of the film and terminate on the surface as characteristic lines, determine the location and orientation of 180^∘ and 90^∘ domain walls. The results emphasize the crucial role of nanoscale crystalline defects in determining the AF domains and domain walls, and provide a route to optimizing device performance.

The present work points out the importance of chemical heterogeneity on the destabilization of austenitic structure and the formation of deformation induced martensite (DIM) in AISI 300 grade austenitic stainless steels (ASSs) of different level of austenite stability (316L, 304, 301LN). Color etching reveals that the structure of wrought Cr–Ni type steels is never fully chemically homogeneous. Confrontation of distribution and morphology of DIM formed in the volume of material after static and cyclic straining under well controlled different conditions with the characteristic local variations in chemical composition of diverse wrought semi-product forms (plates, sheets, bars) proved prominent and very important role of chemical banding in the destabilization of originally fully austenitic structure. This fact should be considered especially when interpreting the results of hydrogen embrittlement tensile testing of Cr–Ni ASSs with lowered Ni content. An impact of chemical heterogeneity on microstructural changes during production of UFG structure of 301LN and its cyclic straining is highlighted

Four blends of Al powder containing different amounts of Ti were deposited onto Ti-46Al-7Nb substrates as oxidation-protection layers using low-pressure cold spray. The coating morphology and chemical composition were assessed. Optimized heat treatment in protective atmosphere was carried out in order to induce formation of intermetallic phases within the deposits. The specimens were then subjected to 950'C exposure for 100, 250, and 500 hrs and their oxidation performance was monitored using the gravimetric method. It was found that the oxidation rate of the coating-protected specimens was substantially reduced (an increase in the weight gain of 1.37 mg/cm2 after 500 hrs of specimen with Al coating) as compared to their uncoated counterparts (1.21 mg/cm2 after 50 hrs at 900'C). The oxidation rates increased with increasing content of Ti in the coatings. Substantial changes of the coating integrity were recorded after the long-term oxidation testing.V rámci této studie byly na substráty slitiny Ti-46Al-7Nb pomocí nízkotlaké technologie kinetického nanášení deponovány čtyři antikorozní vrstvy Al obsahující různá množství Ti. Byla stanovena morfologie a chemické složení vzniklých nástřiků a posléze bylo provedeno optimalizované žíhání vzorků v ochranné atmosféře s cílem tvorby intermetalických fází v nástřicích. Hlavní část studie byla poté dlouhodobá tepelná zátěžová zkouška při 950'C (trvání 100, 250 a 500 hodin), při které byla sledována oxidační odolnost gravimetrickou metodou. Bylo zjištěno, že u depozicí vrstev došlo u vzorků k významnému snížení rychlosti oxidace (nárůst hmotnosti 1.37 mg/cm2 po 500 hod u vzorků s nástřikem Al) ve srovnání s původními, nepovlakovanými vzorky (1.21 mg/cm2 po pouhých 50 hod při 900'C). Rychlost oxidace se se zvyšujícím se obsahem Ti zrychlovala. Po tomto zatěžování rovněž došlo k zásadnímu porušení integrity nástřiků