Characterizing the 3D morphology of nano- and micro-scale precipitates in metallic materials remains challenging. By combining 3D focused ion beam imaging with nondestructive synchrotron x-ray ptychographic tomography, this study pioneers a multi-modal imaging approach that unveils the 3D morphology of NiTi2 precipitates and a previously unknown cross-linked network of Ni4Ti3 precipitates in the nickel-titanium alloys, achieving a spatial resolution of 52 nm. Key discoveries challenge long-standing assumptions: Ni4Ti3 precipitates can form a network rather than isolated ellipsoids through three distinct cross-linking modes. Their shapes are not perfectly lenticular due to overlapping stress fields and loss of coherency. The 3D morphology of NiTi2 precipitates shows that they are primarily spherical and governed by interfacial energy minimization. The competitive growth mechanisms are captured via phase field simulation. These insights deepen the understanding of precipitate growth in NiTi alloys and establish a new paradigm for 3D microstructural imaging.

This study presents a two-stage high shear-strain processing deformation technology, consisting of the intensive plastic deformation method of rotary swaging (RS), in combination with the severe plastic deformation method of continuous equal channel angular pressing (ECAP-Conform). The designed technology is experimentally tested at 25 °C, using a commercially pure titanium. Before each individual processing step, uniaxial compression testing is used to acquire stress–strain datasets to subsequently calculate the Hensel–Spittel rheology laws for both of the processing steps. These rheology models are further used to assemble Finite Element Analyses to numerically examine the stress–strain development within the studied material. The study also investigates and characterizes selected deformation parameters. Further, the predicted results are then put in correlation with the experimentally observed (sub)substructure development. The study documents that pre-processing via two passes of rotary swaging has highly positive effects on the substructure development and microstructure homogenization within the titanium workpiece, when compared to a workpiece subjected to just a single pass of ECAP-Conform. The unprocessed Ti and the Ti subjected to RS and ECAP-Conform exhibited faster work-hardening and higher flow stress than the Ti subjected solely to RS. The results also show that the two-stage high shear-strain processed titanium exhibited significantly higher homogeneity of distribution of the imposed strain than a conventional titanium subjected solely to ECAP-Conform. As confirmed by the numerical analyses, the nature of the material plastic flow during RS affected positively the homogeneity after ECAP-Conform.

Modern electroconductive materials involve copper-based carbon-enhanced composites featuring convenient mechanical properties and, simultaneously, favorable electric conductivity. Such composites can be processed by deformation/thermomechanical treatments to introduce advantageous microstructures, further enhancing their performance. The study features powder-based copper-carbon (Cu/C) composites, fabricated from chemical vapor deposition-prepared powder mixture by a direct consolidation using the rotary swaging method, which enables to eliminate the typical (costly and time consuming) preparation steps of consolidation and sintering. The directly consolidated Cu/C composites were further processed by the severe plastic deformation method of high-pressure torsion (HPT), introducing severe shear strain and high pressure and thus providing fine-grained microstructures. The consolidated composites were processed with two HPT revolutions. The results showed that the final microstructures and properties were primarily influenced by the carbon content within the prepared powder mixture; although the HPT-processed composites featured homogeneous fine-grained microstructures with the average grain sizes of 2-3 & micro;m, the sizes of the graphene particles varied. The Vickers microhardness exceeded 100 HV0.1 for all the samples, and the electric conductivity varied between 98.8% and 102.1% IACS (International Annealed Copper Standard).

Multi-material structures have shown great versatility in wide applications. However, additive manufacturing of multi-metal mechanical composite structures is challenging. Beyond this, a comprehensive and multi-scale understanding of the fracture mechanisms in such structures has not been sufficiently elucidated. In this study, we exploited synchrotron phase contrast X-ray computed tomography and synchrotron X-ray ptychographic tomography to achieve in situ, continuous observation of the fracturing process in large-scale brick-and-mortar multi-metal composite structures, resolving phenomena spanning from the micro- to nano- scale. Findings suggest that nano-pores prevailingly exist in additively manufactured metals, and interfacial porosity as a transitional geometry between different materials can retard the crack growth and improve fracture toughness. This multi-scale study directly informs the designing, manufacturing, and testing of multi-metal composite structures.

In the scope of this study, the effects of selected routes of thermomechanical post-processing performed via rotary swaging on the overall performance of additively manufactured AISI 316L stainless steel were evaluated. The acquired results showed that both the swaging ratio and temperature affected the development of microstructure and precipitation, as well as influenced grains morphology, size, and orientations, all of which had effects on the corrosion and mechanical behaviours of the original workpieces. Increasing the swaging ratio and decreasing the processing temperature generally supported grain refinement and increased the strength (UTS), although increasing the processing temperature supported plasticity. The microstructure of the piece processed by cryogenic swaging with the ratio of 1.0 displayed the smallest grains (mean size of 2.4 mu m), well-developed substructure, and finest dispersion of precipitates, which increased the mechanical properties (UTS of similar to 2100 MPa) and lowered the overall tendency for intergranular corrosion. This piece also exhibited the most favourable corrosion resistance. Nevertheless, swaging under hot conditions already significantly refined the grains, and increased the UTS approximately by 300 % (swaging ratio of 0.7), resp. 400 % (swaging ratio of 1.0) compared to the additively manufactured workpiece (UTS of 283 MPa). The cold swaged pieces also featured refined grains, and exhibited both enhanced strength and increased plasticity.

Preparation of metallic materials via laser powder bed fusion has gained high popularity primarily due to the versatility of the processed materials and the complexity of the available component geometries. However, the prepared components feature characteristic shortcomings. Among the ways to successfully reduce/eliminate printing issues and homogenize the properties within additively prepared materials is optimized post-processing. In this study, we present the positive effects of deformation post-processing at ambient (room) temperature on the microstructure and mechanical properties of AISI 316L stainless steel prepared by laser powder bed fusion. The post-processing was performed by the industrially applicable method of rotary swaging, for which varying swaging degrees were applied. The selected swaging degree influenced primarily the interactions between the dynamic strengthening and softening processes and consequently the strength/plasticity ratio, although all the applied swaging degrees successfully eliminated the residual porosity and imparted (sub)structure development and grain refinement. The ultimate tensile strength (UTS) for the original workpiece was 282 MPa, and it increased up to more than 1400 MPa after the final swaging while maintaining favorable plasticity (elongation to failure over 30%). The study thus proposes a way to successfully enhance the performance of additively manufactured AISI 316L steel with the use of a commercially applicable plastic deformation technology.

Additive manufacturing is known for its ability to create components with complex shapes. It is a promising technology, for example, in the production of components from the superalloy Inconel 718. However, compared to the production by conventional processes, additive manufacturing suffers from structural deficiencies, such as pores and residual stresses. These can affect the otherwise excellent creep resistance of the Inconel 718. Previous studies have shown that the application of postprocessing in the form of intensive plastic deformation leads to significant improvements in the structure produced by additive manufacturing. This study investigates the effect of rotary swaging on the microstructure and creep behavior of additively and conventionally manufactured Inconel 718. The experimental methodology of accelerated creep testing consisted of a slow cyclic plastic deformation of a material under long-term stress at an elevated temperature of 750 °C. Rotary swaging significantly contributed to grain refinements and the microstructure homogenization of both materials. The conventionally manufactured material exhibited the highest creep resistance, especially after rotary swaging. In contrast, the additive manufactured material exhibited a shorter creep lifetime, even despite of rotary swaging. It turns out that creep resistance in additive manufacturing combined with rotary swaging is influenced by a combination of several opposing phenomena, such as the proportion of high angle grain boundaries. These on the one hand can improve creep properties by increasing resistance to dislocation-mediated deformation. However, on the other hand, it can lead to a decrease in creep resistance by promoting grain-boundary sliding, elemental segregation, and cavity nucleation.

Rotary swaging (R-SWG) was used to tailor the microstructure and residual-stress state of magnesium alloys through combined radial compression and shear deformation. This work compares five thermomechanical R-SWG routes applied to permanent mold-cast AZ91 containing 0.03 wt% B in order to establish route-dependent relationships between microstructure, texture, residual stresses and compressive response. The investigated routes combined different second-pass temperatures, feeding rates, prior T4 treatment and total reductions. The route-dependent differences in grain refinement and radial microstructure heterogeneity have been revealed using electron microscopy. All processed conditions developed pronounced textures with distinct central-peripheral variations. Neutron diffraction resolved the residual-stress distributions across the full specimen cross-sections and showed that the finest microstructure did not necessarily coincide with the largest residual-stress gradients. Compared with the initial cast state, rotary swaging increased the compressive yield strength to approximately 240–290 MPa and substantially enhanced the strain to fracture, while Young’s modulus remained within 42–47 GPa. Finite element modeling (FEM) provided a physically consistent interpretation of route-dependent material flow, effective-strain penetration and temperature evolution. The study demonstrates that different thermomechanical R-SWG routes generate distinct process-structure-stress-property relationships in boron-modified AZ91 and highlights the value of full-cross-sectional neutron-diffraction residual-stress mapping as a complement to local microstructure characterization.

The study characterizes the effects of intensive plastic deformation, realized by the rotary swaging method, on the deformation behavior of WNiCo tungsten heavy alloy samples. To assess the differences in the deformation behaviors of the samples, evaluated via uniaxial compression tests (UCT), and characterize the microstructures, i. e. occurrence and development of hardening/softening processes, two different temperatures of swaging (900 °C and 1200 °C), and two different uniaxial compression testing temperatures (1100 °C and 1200 °C), were used. A relatively high strain rate of 10 s −1 was chosen for the testing because of the typical use of the tungsten heavy alloy for kinetic penetrators. The achieved results indicate that the development of softening processes, especially dynamic recrystallization, can occur within the swaged material, depending on the processing/testing conditions. Swaging at the lower temperature of 900 °C introduced significant work hardening and accumulation of strain, which promoted the development of dynamic recrystallization during the subsequent hot temperature testing. Swaging at 1200 °C, on the other hand, facilitated dynamic recrystallization and relaxation (especially within the nickel‐cobalt matrix) already during processing, which consequently increased the activation energy necessary for the development of recrystallization during the hot testing.

Methods of laser powder bed fusion (LPBF) are popular although LPBF components feature issues negatively affecting their mechanical properties and corrosion behaviour. Post-processing of LPBF materials by deformation treatments can reduce/eliminate printing defects and enhance their performance. The study examines the effects of post-processing of LPBF AISI 316L steel workpieces, performed by the intensive plastic deformation method of rotary swaging, on the microstructures, mechanical properties, and corrosion behaviour. The results showed that the applied post-processing introduced grain refinement (cryogenic swaging to the ultra-fine scale) and grain size homogenization, as well as generally enhanced the resistance against corrosion and increased Vickers microhardness of the LPBF steel. The increased corrosion resistance of the cryo swaged sample was, most probably, primarily caused by the formation of {111}<110> shear fibre texture, while for the hot swaged sample, the increased corrosion resistance could primarily be attributed to the recrystallized microstructure. Hot compression testing revealed that the hot swaged sample featured higher activation energy for recrystallization than the cryo swaged one. On the other hand, the energy accumulated within the ultra-fine grained cryo swaged sample, due to aggravated plastic flow during processing, promoted the development of dynamic recrystallization during the hot compression testing.

AISI 316L stainless steel, widely used in numerous industrial fields, can be fabricated by conventional methods, but also by additive manufacturing. As materials prepared by additive manufacturing typically feature various printing defects deteriorating their mechanical and utility properties, post-processing by plastic deformation is able to enhance their performance. The determination of optimized post-processing conditions can advantageously be performed by combining experimental work and numerical simulations using the finite element method. The presented research focuses on investigating the deformation behavior of AISI 316L stainless steel prepared by additive manufacturing under a variety of thermomechanical conditions (temperatures of 900–1250 °C, strain rates of 0.1–100 s−1). Together with the deformation behavior of the steel, the kinetics of the occurring softening processes is also discussed. The experimentally acquired data are further used for numerical simulations to predict the expected magnitudes of force and imposed strains during prospective post-processing. Observing the microstructures and mechanical properties reveals that the prospective post-processing of AISI 316L stainless steel, prepared by additive manufacturing, via plastic deformation is the most favorable when performed at the temperature of 900 °C and using high strain rates. The flow stress/microhardness generally increase at lower temperatures and higher strain rates, as a result of the development of a substructure. On the contrary, higher temperatures support the recrystallization of grains and their coarsening, which consequently decreases the mechanical properties.

Given by their low weight and favorable combination of properties, Al-Fe-Si-based intermetallic and duplex alloys are widely used in mechanical engineering. The use of aluminum scrap for their production imparts the necessity for a thorough study of the impacts of presence of impurity/alloying elements on the phase composition. By this reason, individual impacts of the impurity/alloying elements present in the majority of commercial alloys on phase compositions of the alloys were studied herein. Particular emphasis was on the formation of the α phase and features of the α↔β transformation, as well as on their effects on the solidus, liquidus, and phase transformation temperatures. Modeling was used to study the synergistic effect of the simultaneous introduction of 12 elements into aluminum. According to the results, magnesium, copper, and nickel have a tendency to form combined intermetallic phases, and beryllium, as a structurally free element, forms precipitates even at minimum concentrations. Verification of the modelled results was performed using a real alloy prepared experimentally from commercially available raw materials. The comparison of the results provided by computer modeling and the actual phase composition showed sufficient agreement. The herein acquired results contribute to a deeper understanding of the features of phase transitions occurring during alloying of aluminum alloys and will also be useful for predicting microstructures and phase compositions of intermetallic alloys. This research has potential to inspire further development in materials science and engineering.

The purity of a steel is an important factor influencing the quality of the final products. Therefore, it is important to optimize the existing and develop new steelmaking technologies that affect the resulting purity. Electro slag remelting is a technology of tertiary metallurgy, which can advantageously be used to fabricate high quality steels. The study presents selected theoretical aspects of oxide systems and their specific influences on effectiveness of the electro slag remelting technology. The aim of this work was to experimentally analyze the purity of a tool steel fabricated by electro slag remelting using two different oxide systems (fused slags). The core of the study is the determination of the overall presence of elements in the steels, a thorough investigation of the presence of (not only) oxide-based inclusions within the investigated tool steel, and a detailed analysis of their chemical composition, including the size of these non-metallic inclusions, using energy dispersive X-ray (EDX) on the scanning electron microscope (SEM). Last but not least, the determination of the modification of the occurring non-metallic inclusions and verification of the experimentally acquired results as well as the calculation of the liquid and solid temperature and the calculation of the viscosity of the slags using the FactSage calculation software was performed. The results showed that the used slag influenced especially the occurrence of Mg and Al-based oxide inclusions. The CaS-type inclusions were present within all of the examined samples. The slag type influenced not only the typical morphology and size of the inclusions (especially of the CaS type), but also the tendency of the steel to exhibit localized corrosion when exposed to the ambient environment. This research can contribute to a better understanding of the effect of oxidation systems on the resulting purity and properties of ESR steels, thereby advancing the production of tool steels with higher quality and performance requirements.

Tungsten heavy alloys are favoured for demanding components subjected to extreme operating conditions. In this study we investigate experimentally and via numerical predictions the effects of rotary swaging performed at selected temperatures on the material plastic flow, (micro)structure, and room and high temperature quasistatic and dynamic mechanical behaviour of the WNiCo powder-based pseudo-alloy. The results showed that the green sintered piece featured superior plasticity, but relatively low strength across the variety of testing conditions (e.g. room temperature yield strength of 800 MPa). Swaging at 900 degrees C introduced dynamic recrystallization within the gamma-phase NiCo matrix but did not remarkably affect the W agglomerates; the softened matrix and W agglomerates featuring accumulated strain provided the pieces swaged at 900 degrees C with exceptional strength at room and elevated temperatures (room temperature yield strength of 1 650 MPa). On the other hand, swaging at 1 150 degrees C introduced softening within the W agglomerates and secondary recrystallization of the NiCo matrix, by the effect of which this piece featured both, enhanced plasticity and strength. According to the numerical predictions, increasing the swaging temperature also facilitated the plastic flow and homogenized the imposed strain. However, the piece swaged at 1 150 degrees C exhibited increased surface oxidation and thus deteriorated surface quality.

Additive manufacturing represents a promising alternative to the conventional technologies used for the production of metallic materials. However, in contrast to the conventional approaches, materials produced using additive manufacturing typically feature certain disadvantages. One possibility to reduce their negative effects is to subject the additively manufactured materials to post processing via intensive plastic deformation. The present work primarily studies the creep behavior of Inconel 718, a nickel-based superalloy with a wide applicability in challenging industries, at four different initial material states (additive and conventional manufacturing, and subsequent post-processing via rotary swaging). A rather unique plastometric experimental methodology of accelerated creep testing, which consists of a slow plastic deformation of a material under long-term stress at an elevated temperature, was then used to study the behavior of the prepared samples.

This study presents a multifacet analysis of the microstructural mechanics revealing the thermomechanical processing effects on the impact deformation of ANSI 316L stainless steel. The raw material is additively manufactured by laser powder bed fusion. Samples of three states are studied: as‐printed (AP), postprocessed via cold rotary swaging (CRS), and postprocessed via hot rotary swaging (HRS). A series of state‐of‐the‐art techniques are employed to evaluate the microstructural properties. This includes the quantification of residual strain (via neutron and X‐ray diffraction), substructure development (via electron microscopy), porosity (via X‐ray tomography), and microhardness (via indentation). The important findings are: 1) The AP sample features characteristic distributions of residual strain (i.e., tension around the cylinder edge, compression toward the core) and numerous pores; 2) postprocessing via HRS homogenizes the microstructure and eliminated porosity, while CRS causes significant grain refinement and increase in the microhardness but does not significantly reduce porosity; 3) impact deformation induces intensive hardening in the CRS and HRS sample, that they show up to 380 HV1 and 420 HV1 in microhardness; 4) on the contrary, the AP material retains its homogeneity after impact deformation. These important results shed light on enhancing the impact performance of additively manufactured steel through thermomechanical postprocessing.

Although methods of additive manufacturing have recently become very popular, 3D printed components contain major porosities that significantly deteriorate local material properties. To circumvent this, 3D printed materials can advantageously be thermo-mechanically post-processed in various ways. The presented research is focused on assessing the changes in material properties (porosity, mechanical properties and internal stress) that are related to changes in structures caused by varying the post-processing conditions. Besides, the effects of the selected preparation technology on wear caused by abrasive water jet (AWJ) are studied. Wearing is investigated on AISI 316L steel samples fabricated by selective laser melting (SLM), some of which are in the as-printed state, while others were subjected to thermal or thermos-mechanical treatments; i.e. processed via the rotary swaging method either cooled to liquid nitrogen temperature, or heated to 900 degrees C. The AWJ wear evaluation is carried out by comparing the declination angle, which can be measured via observing the unevenness of the cut walls (the angle between the axis of the incident jet and the tangent to the curve of the asperity created on the wall during penetration of the jet through the material). If this angle is determined at an identical depth from the point of jet penetration into the material and for an identical configuration of the abrasive water jet, it can be advantageously used for wear evaluation. As this angle is also related to strength and hardness of a material, it can be used to relatively easily compare the results acquired for various samples taken from an identical material.

The utilization of additively manufactured materials has increased. Knowledge of the behaviour of this prepared material is crucial to designing safe structures and products. However, the properties are different from those of conventionally produced materials. Therefore, the focus is on widely used AISI 316L austenitic stainless steel to present its plasticity and ductile fracture, crucial in decision-making within the design process. The additively manufactured specimens were machined and also left as built, as it is not always economical to machine all the surfaces, which can even be impossible in some cases. However, it has been shown that the machining can be detrimental in some cases. First of all, the stress–strain behaviour was studied in order to simulate all the experiments. Then, several ductile fracture criteria were calibrated using these simulations and mutually compared for three studied material states—conventionally wrought (rolled), as built and machined after printing. The material prepared by the laser powder bed fusion technology exhibited higher yield strength compared to that of the wrought material. The results further show a significant difference when it comes to ductility, which is highest for wrought material and lowest for printed material that was machined. The study also provides information on the mechanisms of hardening and failure with fractography performed to support the findings for widespread austenitic stainless steel.

Improving the mechanical properties of copper and graphene composites is of a high interest. In accordance with the Hall–Petch law, the finer the grains, the higher the strength of material. Direct consolidation of fine powders is thus highly promising for preparation of (ultra)fine‐grained copper composites featuring more or less homogeneous distributions of graphene particles. This study is original as it investigates the feasibility of using the industrially applicable intensive plastic deformation method of rotary swaging for direct consolidation of copper–graphene composites featuring enhanced performance. The results show that the swaging ratio of 1.4 results in a satisfactory consolidation of the powders. However, the final consolidated piece swages with the swaging ratio of 2.8 features a relatively high microhardness of 108.2 HV0.05 and, simultaneously, the electric conductivity of 94.6% International Annealed Copper Standard (IACS). The microstructure, featuring graphene particles more or less homogeneously distributed along the grain boundaries, consists of fine grains and numerous strengthening twins, the formation of which is supported as the graphene particles aggravate the movement of dislocations along the preferential slip systems. The occurring structural phenomena (grain boundaries, twinning, texture, etc.) directly influence the mechanical (microhardness), physical (dilatation), and electric properties of the composite.

Cu-based alloys and composites are popular to prepare electroconductive parts. However, their processing can be challenging, especially in case of composites strengthened with oxides. To save the necessary time and costs, numerical simulations can be of help when determining the deformation behaviour of (newly introduced) materials. The study presents a combined method of strengthening of Cu by adding 5 wt.% of La2O3 particles and performing shear-based deformation by equal channel angular pressing (ECAP). The effects of the method on the microstructure, mechanical properties, and thermal stability of the composite are examined both numerically and experimentally. The results showed that the La2O3 addition caused the maximum imposed strain to be higher for the composite than for commercially pure Cu, which led to the development of subgrains and shear bands within the microstructure, and a consequent increase in microhardness. The numerical predictions revealed that the observed differences could be explained by the differences in the material plastic flow (comparing the composite to commercially pure Cu). The work hardening supported by the addition of La2O3 led to a significant increase in stress and punch load during processing, as well as contributed to a slight increase in deformation temperature in the main deformation zone of the ECAP die. Certain inhomogeneity of the parameters of interest across the processed workpiece was observed. Nevertheless, such inhomogeneity is typical for the ECAP process and steps prospectively leading to its elimination are proposed.