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The enhancement of the mechanical properties of an alloy is often accompanied by a decrease in corrosion resistance. Therefore, in this paper, thermal-cold cycling (TCC) treatment was used to process 7075-T83 aluminum alloy to improve its corrosion resistance on the basis of ensuring its mechanical properties. Intergranular corrosion (IGC) and electrochemical tests combined with transmission electron microscopy observation were carried out to investigate the effect of TCC treatment on the microstructure and corrosion resistance of the 7075-T83 aluminum alloy. The results showed that the corrosion resistance of the alloy was significantly improved and the microstructure was well optimized after two TCC treatments. The IGC depth of the alloy was the shallowest, at 25.8 μm, and the corrosion current density and corrosion rate reached the minimum values of 0.00148 mA/cm2 and 0.0484 mm/a, respectively. In addition, the average diameter of the matrix precipitates was the smallest, the volume fraction was the highest, the thickness of the passive film formed on the surface of the alloy was the thickest, reaching 3.81 nm, which effectively resisted the erosion of Cl−, while the agglomeration and coarsening of the grain boundary precipitates and the size and the distance between them increased, exhibiting a discontinuous distribution, which blocked the anodic corrosion channel and hindered the corrosion progress, thus improving the corrosion resistance of the alloy. [ABSTRACT FROM AUTHOR]

Grain size has a significant impact on the superelasticity of alloys. Large-sized grains show superior superelastic properties because the grain boundaries are minimized and the grain constraints caused by triple junctions are reduced. Cyclic heat treatment (CHT) is commonly employed to generate subgrains, whose energy can be consumed to induce abnormal grain growth (AGG) and obtain large-sized grains. In this paper, the effects of adding Cu on the subgrain characteristics during AGG and microstructural evolution of FeMnAlNi-based superelastic alloys were systematically investigated. The addition of Cu reduced the temperature at which the γ phase precipitates and altered the morphology of the γ phase. After the dissolution of the refined γ phases, the average subgrain size became smaller and misorientation increased. These characteristic subgrain changes improved the driving force for AGG and accelerated the grain boundary migration rate. Due to the addition of Cu, the maximum grain size reached 28.2 mm. This study provides a new method for the preparation of FeMnAlNi-based superelastic alloys with large-sized grains. [ABSTRACT FROM AUTHOR]

Ductility dip cracking (DDC) is a solid-state failure occurring during multi-pass solidification processes (e.g., welding, additive manufacturing) for FCC alloys that exhibit a distinct dip in their ductility at intermediate temperatures. While the phenomenon has been studied for over a century, the majority of current research focuses on a subset of DDC-susceptible FCC alloys (Ni–Cr–Fe). The review paper herein presents an analysis of published data to evaluate the current state of understanding regarding the materials mechanisms at work. Recent advances in test methods have permitted highly controlled approaches for testing and quantifying DDC, but the wide range of unique tests often provide conflicting results regarding the fundamental materials behaviors and underlying mechanisms. At present, three mechanisms have been proposed for DDC: grain boundary sliding, precipitate-induced strain, and impurity element segregation. While the majority of published studies support grain boundary sliding as the primary mechanism of DDC, an examination of the aggregate data available across multiple studies suggests combinatorial impact of simultaneous (and competing) mechanisms for DDC. Further, the long-held assumptions regarding the negative impact of key alloying elements become less convincing when comparing results across studies. There are considerable future opportunities for research on DDC behaviors in other alloy systems, and there are a lacunae of data when considering the effect of welding process parameters on DDC and the use of modeling and simulation approaches to understand the DDC behavior in the highly susceptible FCC alloy systems. [ABSTRACT FROM AUTHOR]

This paper utilizes the dynamic material model (DMM) to construct a hot working diagram, investigating the microstructural evolution within the deformation zone in the temperature range of 750–1100°C and strain rate range of 0.1–20 s−1. The hot working diagram delineates the stable processing zone and the rheological instability zone, with distinct processing parameters leading to varied internal deformation mechanisms. The high-power dissipation zone (η ≥ 0.3) represents a stable processing area where the dominant deformation mechanism is dynamic recrystallization (DRX), occurring at a deformation temperature of 980–1100°C and a strain rate of 0.1–5 s−1. Higher temperatures and lower strain rates facilitate the nucleation of DRX, resulting in a microstructure characterized by complete DRX grains. Moreover, increasing deformation temperature and decreasing strain rate lead to larger DRX grain sizes. In the temperature range of 900–980°C and across all strain rates, the medium power dissipation zone (0.2 ≤ η < 0.3) exhibits a deformation mechanism resulting from the combined effects of dynamic recovery (DRV) and DRX. Numerous small grains initiate at the initial grain boundaries, forming a necklace structure wherein sawtooth or protruding grain boundaries indicate the initiation of DRX. Within the rheological instability zone (η < 0.2), characterized by temperatures below 900°C, the microstructure is comprised of elongated deformed grains accompanied by localized shear bands along the grain boundaries. [ABSTRACT FROM AUTHOR]

It is vital to reveal the effect of microstructure features on the corrosion behavior of pure aluminum anode in alkaline electrolyte for Al-air batteries. In this paper, we extensively studied the influence of mechanical deformation on the corrosion microstructure and then corrosion features of pure aluminum anode. The results demonstrate that the cold-rolling deformation could facilitate the grain size refinement of pure aluminum. Surprisingly, the aluminum anodes with smaller grain sizes and larger grain boundary areas could effectively improve the corrosion resistance. The further characterization of the microstructure indicates that the deformation is capable of causing the fracture of the cathodic secondary phase precipitate clusters thus weakening the galvanic corrosion effects. The results of this paper could gain insights into the design and processing of pure aluminum for Al-air battery. [ABSTRACT FROM AUTHOR]

The mechanical properties of the materials are determined by the size and morphology of fine microscopic features. Quantitative microstructural analysis is a key factor to establish the correlation between the mechanical properties and the thermomechanical treatment under which material condition has been achieved. As such, microstructural analysis is a very important and complex task within the manufacturing sector. Published standards are used for metallographic analysis but typically involve extensive manual interpretation of grain boundaries, resulting in measurements that are slow to produce, difficult to repeat and highly subjective. Computer vision and the evolution of artificial intelligence in the past decade can offer solutions to such problems. Deep learning and digital image processing techniques allow digital microstructural analysis to be automated using a fast and repeatable method. This paper proposes a novel boundary class semantic segmentation approach (BCSS) to identify each phase of the microstructure and additionally estimate the location of the grain boundaries. The BCSS is then combined with more traditional segmentation techniques based on the Watershed Transform to improve the identification and measurement of each feature within the microstructure using a new, hybrid automated digital microstructure analysis approach. The new method is validated on a published dataset of two-phase titanium alloy microstructure pictures captured using a scanning electron microscope. Measurements match the level of accuracy of accepted manual standards, and the method is demonstrated to be more reliable than other automated approaches. The influence of the subjective nature of manual labelling, required to train the proposed network, is also evaluated. [ABSTRACT FROM AUTHOR]

In the chemical mechanical polishing (CMP) process, chemical action is generally determined by pH regulator and oxidant in the polishing slurry. In this paper, tungsten (W) polished by CMP was examined, and the material removal mechanism was discussed. The influence of pH values and hydrogen peroxide (H2O2) concentrations on surface quality and material removal rate (MRR) were closely investigated. The MRR obtained from the CMP test indicates that the removal rate of W by the H2O2 oxidant reaches 34.10 μm/h under acidic pH conditions and the H2O2 oxidant improves the polishing rate of W. The obtained potentiodynamic polarization results show that the passivation layer formed under the H2O2 action cannot prevent the further corrosion of the slurry to the sample, but W can stably generate a tungsten trioxide (WO3) passivation layer under acidic conditions. XPS data confirm that the formation and dissolution of tungsten oxide passivation layers with different compositions are the main causes of these results. By analyzing the different morphologies (corrosion pits, grain boundaries, etc.) formed after tungsten chemical mechanical polishing (W-CMP), the deformation and removal mechanisms involved in the process are more deliberately exposed. This study enriches the understanding of the corrosion damage and material removal mechanisms of pure tungsten during CMP and contributes to the efficient and high-precision manufacturing of W components. [ABSTRACT FROM AUTHOR]

Electron powder bed fusion (EPBF), as one of the common additive manufacturing techniques, has received increasing attention. EPBF-processed Ti-6Al-4V is widely used in biomedical and aerospace industries. However, titanium alloys prepared by EPBF have large pores and poor corrosion resistance. Heat treatment is a simple and non-polluting way to improve material properties. However, the effect of heat treatment on the corrosion resistance of EPBF-processed Ti-6Al-4V alloy has not been thoroughly researched. In this paper, Ti-6Al-4V samples processed by EPBF were treated with different heat treatment methods. All corrosion tests were performed in 3.5 wt.% NaCl solution at ambient temperature. HT800 has the highest content of β phase, and the smallest grain boundary density, and therefore has the best corrosion resistance. The corrosion current of HT800 is reduced from 0.109 µA/cm2 unheated to 0.022 µA/cm2, a reduction of 79.82%. [ABSTRACT FROM AUTHOR]

The alloy composition and sensitization behavior are crucial factors that cannot be overlooked in Al–Mg alloys. The effect of Zn addition on mechanical properties and sensitization behavior of 5083 alloy was investigated by tensile tests, weight loss experiments, and first-principles calculation in this paper. The results show that Zn can significantly improve the strength and sensitization behavior of the alloy. The tensile strength of the cold-rolled alloy increased from 459 to 498 MPa with the addition of 1.5%Zn. Furthermore, by incorporating 2.0% Zn, the mass loss of the cold-rolled alloy after sensitization at 170℃/1 h decreased from 49.3 mg·cm−2 to 19.5 mg·cm−2. First-principles calculations indicate that Mg clusters can only exist stably near grain boundaries, while Mg–Zn clusters can exist stably both within and at grain boundaries. This reduces the number of corrosive media at grain boundaries and weakens their continuity. Moreover, the energy barrier that T-phase precipitation needs to overcome during precipitation is lower than β-phase, which transforms the stabilization schedule of the alloy from 240℃/12 h without Zn to that 210℃/4 h with 2.0% Zn-containing. The synergistic effects of Zn content and sensitization on the properties of the alloy were revealed, which sheds some light for the design of the composition and processing method according to application scenarios. [ABSTRACT FROM AUTHOR]

The effect of the grain boundary (GB) misorientation on plastic deformation of Inconel 718 (IN718) alloy was investigated in this paper, using in-situ tensile experiment at 650 °C in combination with crystal plasticity finite element method (CPFEM). The results indicate that dislocations tend to accumulate at GBs to form stress concentration, but the degree of stress concentration does not necessarily increase with the increase of the GB misorientation. It is attributed to the slip transfer at the GBs, determined by the angle between the slip systems of the two adjacent grains. There is a significant uncertainty in the slip transfer for GB misorientation larger than 10°. However, the m α β ′ SF α + SF β criterion, which is a function of the Luster and Morris m α β ′ combining the Schmid factors of the two slip systems with the GB misorientation, has some statistical separation significance. Slip transfer tends to appear at GB misorientation less than 30° and m α β ′ SF α + SF β > 0.78 . This study clarifies the mechanism of the influence of GB misorientation on IN718 microplastic deformation and provides a new strategy to study the deformation behavior of superalloys. [ABSTRACT FROM AUTHOR]

In this paper, engine flywheel shell components of ZL104 aluminum alloy were formed by squeeze casting forming technology, and the effect of process parameters on mechanical properties and microstructure of the formed parts was investigated. Sixteen sets of orthogonal test schemes are designed according to four conditions of specific pressure, holding time, pouring temperature and mold temperature. After the mechanical properties of the castings under different sets of experimental conditions were analyzed, the optimum process parameters were derived from the comprehensive analysis according to tensile strength and elongation. The optimum process parameters involve a casting temperature of 655 °C, a scheme B mold temperature, a pressure holding time of 20 s and a specific pressure of 34 MPa. The average tensile strength and average elongation of the formed flywheel shell components under the optimum process conditions were 211.2 MPa and 7.7%, respectively. The microstructure of the formed parts is mainly composed of α-Al phase and eutectic silicon phase. When the process parameters are properly selected, high mechanical properties and microstructure with little cast defects were obtained in the parts formed by squeeze casting. Except for Al, Fe, Mn and Si elements are mainly enriched at the grain boundary. [ABSTRACT FROM AUTHOR]

In this paper, the deformation mechanisms of a Fe–2.25%Cr–1%Mo (P22) steel are studied after tensile tests at room temperature (RT) and 550 °C (HT), creep-fatigue tests at 550 °C and stress relaxation test at 550 °C (HTSR). The RT, HT and HTSR tests produced permanent strain of about 2.5% by different processes. Deformation features such as the orientation of the grains, local misorientation, grain boundary type and distribution, etc., were characterized using electron backscatter diffraction. Transmission electron microscopy was done subsequently to obtain greater insight into the dislocation substructures. The as-received sample had a ferritic–bainitic microstructure, and a large amount of local misorientation was found in the bainite, indicating plastic strain due to phase transformation. After tensile strain to 2.5% at room temperature, the dislocations formed very small substructures (~100–200 nm) in the ferrite grains, and most of the retained plastic strain seemed to be concentrated in the bainite after deformation. Both the ferrite and bainite showed much lower local misorientation and dislocation wall content after a tensile test to 2.5% strain at 550 °C. Compared to the RT tensile sample, after creep-fatigue at 550 °C, the substructures in ferrite opened up considerably and formed small-angle grain boundaries, with clean areas as large as 20–25 μm. After stress relaxation at 550 °C, the ferrite displayed even less substructure, while the bainite seemed to have greater amounts of local misorientation than in the creep-fatigue case. However, the degree of misorientation was less pronounced than in the room temperature tensile case. These results have been discussed with respect to the causes behind the phenomena observed herein and their possible effects on mechanical behaviour. [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental study of L10-FePt granular films with crystalline boron nitride (BN) grain boundary materials for heat assisted magnetic recording (HAMR). It is found that application of a RF substrate bias (VDC = -15 V) yields the formation of hexagonal boron nitride (h-BN) nanosheets in grain boundaries, facilitating the columnar growth of FePt grains during sputtering at high temperatures. The h-BN monolayers conform to the side surfaces of columnar FePt grains, completely encircling individual FePt grains. The resulting core–shell FePt-(h-BN) nanostructures appear to be highly promising for HAMR application. The high thermal stability of h-BN grain boundaries allows the deposition temperature to be as high as 650℃ such that high order parameters of FePt L10 phase have been obtained. For the fabricated FePt-(h-BN) thin film, excellent granular microstructure with FePt grains of 6.5 nm in diameter and 11.5 nm in height has been achieved along with good magnetic hysteresis properties. [ABSTRACT FROM AUTHOR]

Boring trepanning association (BTA) deep hole drilling is widely used in machining tube sheet of steam generator. In order to get a better service integrity, the surface quality after machining is required to be higher. In this paper, the effect mechanism of BTA deep hole drilling on the integrity and quality of the machined surface layer of low alloy steel SA508Gr.3Cl.2 for nuclear power is investigated. The results show that the gradient microstructure can be obtained by BTA drilling on the surface of the inner hole, including the recrystallized layer with grain refinement and the plastic deformation layer with high-density sub-crystal structure and grain distortion. With the increase of drilling speed and feed rate, the thickness of deformation layer increases. During the BTA deep hole drilling, the proportion of low-angle grain boundaries (LAGBs) increases with the increasing depth from the machined surface. The increase of drilling speed leads to the increase of recrystallization degree and the proportion of LAGBs in the machined surface. The effect of feed rate on the proportion of LAGBs is opposite. The machined surface is characterized by regular peak and valley, and there are typical surface defects mainly involving feed marks, surface tearing, and plowing grooves. With the increase of drilling speed, the surface roughness will decrease. The effect of feed rate on surface roughness is obviously lower than that of drilling speed. With the increase of drilling speed, and feed rate, the depth of hardened layer increases gradually, which is caused by dislocation strengthening and fine grain–strengthening effect during BTA drilling process. Higher drilling speed is recommended in forming a better machined surface with a strengthening layer of a certain thickness. [ABSTRACT FROM AUTHOR]

Nickel-based single crystal superalloy, which has better comprehensive mechanical properties than polycrystalline superalloy due to the prevention of microcrack generating from grain boundaries, has been widely applied in the hottest components of aeroengine. However, the mechanical machining of nickel-based single crystal superalloy is rarely studied due to the low thermal coefficient, high hardness, and high strength. In order to explore the surface quality of nickel-based single crystal superalloy after milling, surface characteristics and effects of processing parameters of nickel-based single crystal superalloy DD5 after end milling were systematically investigated in this paper. In addition, the effect of milling on the special microstructure composed of matrix phase γ and ordered precipitated phase γ′ in DD5 was studied by observing the subsurface after milling. The results show that the microstructure γ and γ′ phases distorted to a certain extent, and deducing a plastic deformation layer. In the region close to the machined surface, γ and γ′ phases were severely deformed and difficult to distinguish, forming a hardened layer. For revealing the material removal mechanism of DD5, chip morphology formed during milling were observed. The lamellar structure was found on the chip surface due to the adiabatic shear, illustrating the plastic removal is the dominant removal mechanism of DD5. This work provides a basis for analyzing the milling ability of nickel-based single crystal superalloy and provides technical supports for improving the machining quality. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a method of strengthening Sn-based solder to retard the microstructural evolution during thermal cycling and thus to improve the thermal fatigue life of Sn-based solder joint. We fabricated a multiple-elemental Sn-based solder by adding Ni, Bi and Sb into the Sn3.0%Ag0.5%Cu (SAC305) solder. Thermal cycling tests (− 55 °C ~ 150 °C) were performed on the prepared multiple-elemental Sn-based solder joints and SAC305 solder joints, and quasi-in situ observation was accompanied by the thermal cycling test to identify and compare the corresponding microstructural evolution process. It turned out that the intragranular dislocation movements were effectively hindered at the early stage of thermal cycling, which was due to the effects of solid solution strengthening. Furthermore, the motion of pre-existing grain boundaries and hysteresis of dislocation slip played a predominated role in the strengthened multiple-elemental solder joints. By contrast, the aforementioned two phenomena occurred concurrently in the non-strengthened solder joints. As a consequence, the multiple-elemental solder joints retained the integrity of solder joints after 1200 thermal cycles. This phenomenon indicates that the microstructural evolution was significantly delayed compared with the pristine SAC305 solder joints during thermal cycling. Therefore, SACNSB solder joints have a longer thermal fatigue life. The idea of retarding microstructure evolution during thermal cycling by strengthening Sn matrix can help open a new pathway to improve thermal fatigue life of Sn-based solder joints. [ABSTRACT FROM AUTHOR]

This study delves into the variation in the fundamental aspects of electrical quantities with the partial substitution of Tm impurities at Bi-site in the Bi2.1-xTmxSr2.0Ca1.1Cu2.0Oy (0.00 ≤ x ≤ 0.30) ceramic system with the derivatives of electrical resistivity examinations and theoretical approaches. It is found that all the electrical characteristic properties tend to improve with the trivalent Bi/Tm substitution level up to x = 0.07 beyond which they degrade considerably due to the increment of non-superconducting barrier regions, permanent disorders, inhomogeneity, porosity, grain misorientation distribution, internal and surface omnipresent defects, microscopic cracks, and coupling interaction problems throughout the grain boundaries in the Bi-2212 crystal system. Thus, the optimum dopant level of x = 0.07 results in the transition from the over-doped state to optimally doped state in the Bi-2212 crystal system as a consequence of augmented hybridization mechanism. Further, the characteristic two-stage transition temperatures, gap coefficient, Josephson coupled, and thermal energies for the isolated grains and inter-grains are explored. The findings show that the optimum Bi/Tm substitution leads not only to stabilize the superconductivity in the homogeneous superconducting clusters as a result of the increment in the formation of active Cooper pairs but also to decrease significantly the location of resistivity in long-range coherent state due to the increment of hole trap energy. Additionally, a strong link is established between the structural disorders-defects and onset/offset ( T c onset / T c offset ) transition temperatures using the electrical resistivity features for the first time. The empirical model based on the impurity scattering and lattice strain in the crystal lattices displays that it is possible to achieve the possible highest T c onset and T c offset values of about 86.558 K and 86.445 K, respectively. To sum up, the paper with strong methodology between electrical quantities and structural disorders-defects depending on Tm impurity may be a pioneering research to explain why the characteristic features improve with the optimum substitution and especially open up a novel and feasible area for the advanced engineering, heavy industrial technology, and large-scale applications of ceramic materials. [ABSTRACT FROM AUTHOR]

Accurately determining the crack initiation stress (CI) is of great importance to evaluate the stability of deep underground openings and the permeability of host rock in the near field. For this paper, uniaxial compression tests and increasing amplitude cyclic stressing tests were performed on four kinds of rocks with different porosities. The stress-strain data and acoustic emission (AE) data of these tests are analyzed to evaluate the applicability and accuracy of the existing methods for determining the CI. The results demonstrate that for marble and Beishan granite with low porosity, the lateral strain (LS) method is the simplest and most direct method to obtain the CILS. For high porosity sandstone, the result of lateral strain response (LSR) method is significantly smaller than that obtained by AE. The cumulative AE hits (CAEH) method heavily depends on the "S-shaped" characteristic of the cumulative AE hits curve, which limits its scope of application. The cumulative AE hits curve slope (CAHS) method, which determines the key inflection point of the cumulative AE hits curve by slope variation to determine the CICAHS, possesses the widest applicability and highest accuracy. The CI/UCS ratios of rocks with similar grain sizes decreases with increasing porosity. For Beishan granite, the average CICAHS is less than that of CILS. They are 0.43 UCS and 0.53 UCS, respectively. According to the residual strain data from the cyclic loading tests, the two crack initiation thresholds of Beishan granite can be clearly identified. These two crack initiation thresholds represent different crack initiation sequences in grain boundaries and different minerals. [ABSTRACT FROM AUTHOR]

Improvement of the mechanical property of the near-β titanium alloy Ti-10V-2Fe-3Al (TB6) fabricated by laser additive manufacturing can be achieved through solution and aging treatment. In this paper, the changes in the microstructures and mechanical properties of the deposited TB6 specimens were tested by changing the solution temperature, aging temperature, and aging time and the effects of the primary α phase (αp) and secondary α phase (αs) on the mechanical properties were analyzed. The results show that the solution temperatures mainly determine the volume fraction of αp and grain boundary α phase (αGB). Aging temperature and time have large impacts on the morphology of αs. The strength of the solution- and age-treated specimens are controlled by the volume fraction and size of αs. The higher volume fraction, αs, obtained by the higher solution temperature could lead to a higher strength with balanced ductility. The coarser αs obtained by the higher aging temperature or longer aging time will contribute to higher ductility, but decrease the strength of the alloy. The fracture mode of tensile specimens is mainly intergranular fracture due to the strain incompatibility between the grains and the grain boundaries. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of Ti-6Al-4V alloy sintered by spark plasma was studied by multi-pass of hot compression experiment, and the influence of different thermal deformation parameters (hot compression temperature deformation: 950°C–20% for one pass, 850°C–20% for two passes and 900°C–10%/20%/30% for three passes) was studied. The results show that the dynamic recrystallization characteristic behavior appears in the three deformation passes. The microstructure after the first and second pass deformation is mainly composed of Widmanstätten structure. With the increase of strain rate, the thickness of lamellar α decreases gradually. In three pass, the grain boundary α phase and the layered α phase are twisted and bent when the deformation amount is 10% and 20%, and the deformation amount increases to 30%. The spheroidization of lamellar α phase occurs, and the size of β grain decreases obviously. The content of equiaxed α phase and grain size decrease with the increase of strain rate. [ABSTRACT FROM AUTHOR]

Magnesium matrix composites (MMCs), prepared by adding reinforcements to magnesium alloys, are widely noticed for superior properties over the matrix. However, few studies on ZrO2p-reinforced AZ31 magnesium alloys were prepared by the powder metallurgy (PM) method. In this paper, AZ31 magnesium alloys with different ZrO2p contents were successfully prepared by powder metallurgy (PM), and the microstructure and mechanical properties of AZ31 and MMCs were investigated. The results show that ZrO2p hinders the migration of dislocations and forms a particle deformation zone (PDZ) around ZrO2p. The PDZ with higher energy storage can promote the nucleation process of dynamic recrystallization of MMCs. Meanwhile, ZrO2p pins the grain boundaries and hinders the growth of recrystallized grains, so the MMCs have higher recrystallization fractions and finer grains. In addition, the recrystallization process removes dislocation density and promotes the transition from low-angle grain boundaries to high-angle grain boundaries. As a result, the composites have superior properties due to the pinning of dislocations, grain refinement, and load transfer by ZrO2p. Compared with the AZ31 matrix, the UTS, YS, and hardness of the MMCs were increased by ~ 6.8%, ~ 5.0%, and ~ 16.5%, respectively. [ABSTRACT FROM AUTHOR]

Al–Mg alloys undergo sensitization when exposed to elevated temperatures, making them susceptible to intergranular corrosion and stress corrosion cracking. Most of the existing research on microstructure effects on sensitization is centered on the effect of intrinsic grain boundary characteristics such as misorientation angle and coincident site lattice (CSL) values. Very few studies have systematically investigated the influence of extrinsic characteristics such as dislocation density. In this paper, the influence of local microstructure characteristics on the sensitization susceptibility of AA5456 was investigated using in situ optical microscopy corrosion experiments and electron back scattering diffraction analysis. The results show a clear trend between the local geometrically necessary dislocation (GND) density and β phase precipitation, with higher GND densities correlating with higher rates sensitized boundaries. This trend held true even for low angle grain boundaries. These results demonstrate the importance of considering factors beyond grain boundary characteristics in determining susceptibility to sensitization. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization mechanism and microstructure evolution of a novel quasi-continuous network reinforced TiAl matrix composites, TiAl/B4C composites were studied in this paper. The isothermal compression experiments, the scanning electron microscopy, and the electron back-scattered diffraction were carried out. Besides the discontinuous dynamic recrystallization (DDRX), the continuous dynamic recrystallization occurred in γ-phase grains during the loading, characterized by crystal orientation accumulation. Additionally, a large number of 89 ± 3° grain boundaries associated with DDRX also appeared during the loading. With the temperature increasing or/and the strain rate decreasing, the volume fraction of recrystallized grains increased significantly, the < 010 > crystal direction of γ-phase grains within the matrix unit of present composites was gradually parallel to compression direction, and the texture changed from scatter to concentration. The variety of texture was mainly related to different dynamic recrystallization mechanisms in various conditions. [ABSTRACT FROM AUTHOR]

In this paper, resistance element welding (REW) is used to join aluminum and magnesium to solve the problem of brittle intermetallic compounds. The effects of welding current on the nugget formation, element diffusion, and joint performance are investigated. It is found that whether the magnesium alloy sheet is melted or not has an important impact on the joint performance. Both the nugget diameter, ductility, failure load, and energy absorption of the joint increase with the increasing of the welding current when nugget diameter is smaller than the diameter of rivet shank; i.e., the Mg alloy is not melted. When nugget diameter is larger than the diameter of rivet shank, i.e., the Mg alloy starts to melt, the content of Mg element in the weld nugget increases, which gradually increases the hardness and brittleness of the weld nugget. The failure load of the joint increases first and then drops with the increases of welding current because of the tradeoff between the increase of the nugget size and the increase of the nugget brittleness. The fracture surface analysis also indicates that the high current led to the excessive melting of Mg element into the nugget, forming brittle Al–Mg intermetallic compound at the grain boundaries, resulting in the reduction of joint performance. [ABSTRACT FROM AUTHOR]

Grain boundary engineering (GBE) is one of the most successful processing strategies to improve the properties of polycrystalline solids. However, the extensive thermomechanical processes involved during GBE restrict its use to selected applications and materials. In this viewpoint paper, we discuss the opportunity provided by additive manufacturing (AM) technology to broaden the applicability of the GBE paradigm and, consequently, the design space for engineering materials. By integrating specially-designed thermomechanical processing within AM, it would be possible to produce bulk, near-net-shape parts with complex geometry and GBE microstructure. We discuss the major challenges in this endeavor and propose some possible strategies to achieve this goal, which we refer to as "additive-GBE". [ABSTRACT FROM AUTHOR]

We provide a simple geometric theory of crystal growth which predicts the shape and final dihedral angle of three-grain junctions of an augite crystal with two plagioclase grains. The predicted dihedral angle Δ depends on the initial impingement angle ψ formed by the plagioclase grains, and also on the relative growth rates of the augite and the plagioclase, and shows reasonable agreement with data obtained from natural samples. We show that the two augite-plagioclase grain boundaries will normally curve towards each other, which is consistent with the first two types of junction described in the companion paper. However, the third type, the eagle's beak, is formed by the meeting of grain boundaries which curve in the same direction. Although it is possible to account for this type of junction by invoking the localised dissolution of one of the plagioclase grains, this is unlikely to occur. A more plausible explanation involves the late impingement of the two plagioclase grains, consistent with the observation that eagles' beaks are common in gabbros and strongly orthocumulate troctolites, in which the plagioclase framework has not been established by the time augite is growing in substantial quantities. An observed flattening of the curve of Δ values at high values of ψ can be explained by taking into account the importance of interfacial energy in late-stage crystallisation. [ABSTRACT FROM AUTHOR]

In this paper, a theoretical model is established to describe the effect of nanoscale amorphization in nanocrystalline bimaterials on the dislocation emission from the tip of a collinear crack at the interface. In the description, nanoscale amorphization is formed by the splitting transition of the Grain Boundary (GB, the disclination of GBs caused by the movement of GBs). The analytical solution of the model is obtained by the elasticity complex potential solution method. In addition, the effects of nanoscale amorphization, dislocation emission angle, interfacial crack length and material constants of nanocrystalline bimaterials on the critical stress intensity factor of interfacial crack tip corresponding to dislocation emission are discussed through numerical analysis. The analysis shows that the influence of nanoscale amorphization in nanocrystalline bimaterials on the critical stress intensity factor (SIF) corresponding to dislocation emission depends on the dislocation emission angle, the position and size of the nanoscale amorphization, interface crack length and relative shear modulus. With the increase in relative shear modulus and dislocation emission angle, the normalized critical SIF decreases at first and increases afterwards. When the nanoscale amorphization size is small, the critical SIF of the dislocation is less affected, but when the size is larger, the impact becomes great. The influence of nanoscale amorphization on the dislocation emission from collinear interface crack tip is related to nanoscale amorphization and relative shear modulus. There is a critical relative shear modulus that the increase in dislocation intensity has little effect on dislocation emission. Appropriate selection of materials for the upper and lower planes can reduce the critical stress intensity factor corresponding to dislocation emission, thereby promoting the dislocation emission from interface cracks and improving the toughness of the nanocrystalline bimaterials. [ABSTRACT FROM AUTHOR]

Copper filled through silicon via (TSV-Cu) is a crucial technology for chip stacking and three-dimensional (3D) vertical packaging. The multiple thermal loadings caused by the annealing process and deposition of interconnected dielectric layers lead to continuous TSV-Cu protrusions, which can affect its reliability severely. In this paper, the relationship between second protrusion height of TSV-Cu and its microstructur characteristics during double annealing is quantitatively investigated. It is found that grain size of TSV-Cu after annealing once is larger, and the second protrusion value under additional annealing can be greatly reduced. The reduction phenomenon of second protrusion is relative to the microstructure characteristics such as <111> texture and Σ3 grain boundary type. In addition, stress and strain are analyzed by finite element analysis (FEA) to reveal the reduction mechanisms of the second protrusion height of TSV-Cu during double annealing. The initial residual stress of fabricated TSV-Cu and its mechanical property parameters measured by nanoindentation test are incorporated in FEA. The main results show that additional thermal loading leads to a smaller increase of equivalent plastic strain (PEEQ) and von Mises stress if the TSV-Cu is annealed firstly at a high temperature of 400°C. This verifies the second protrusion tendency of TSV-Cu, and explains the reduction mechanisms of the second protrusion height of TSV-Cu. [ABSTRACT FROM AUTHOR]

In order to reveal the different influences between substituting and doping strategies on the dielectric performances of CaCu3Ti4O12 (CCTO) ceramics, the effect of La substituting/doping with different concentrations on the phase structure, morphology, and dielectric performances of CCTO ceramics synthesized by sol–gel route was systematically studied in this paper. The results display that the dielectric constant for La-substituting Ca0.96La0.04Ti4O12.02 and doping CaCu3Ti4O12–0.03La2O3 increases to 8775 and 9225, respectively. Meanwhile, the breakdown field strength of Ca0.96La0.04Ti4O12.02 and CaCu3Ti4O12–0.04La2O3 are 3904 and 3006 V/cm, respectively. Interestingly, both La substituting and doping can lead to extremely low dielectric loss (tanδ) whose minimum value for Ca0.94La0.06Ti4O12.03 and CaCu3Ti4O12–0.02La2O3 are 0.008 and 0.009 at 1 kHz and 20 °C, respectively. More encouragingly, the minimum loss is reduced to 0.0013 at 50 Hz and − 100 °C. These results demonstrate that La substituting is more beneficial to the dielectric properties than doping because substituting can introduce higher grain boundary resistance, grain boundary activation energy, and lower conductivity than doping, which can provide a definite strategy during chemical composition design and manufacture for CCTO ceramics. [ABSTRACT FROM AUTHOR]

Workpiece will face corrosive problems during its application after the manufacturing process. As the common final process, grinding can generate special metamorphic layer on the surface of workpiece and change the initial corrosion resistance of workpiece. In order to study the corrosion resistance of workpiece after grinding process, the paper carries on combining experiment of grinding and electrochemical corrosion. The characteristic of corrosion resistance of grinding is revealed based on the association of grinding mechanism and electrochemical theory. The corrosion potential of workpiece after grinding is higher than matrix, which shows the grinding surface is difficult to begin to corrode. Electrochemical impedance spectroscopy (EIS) shows the grinding surface has large phase angle, impedance and capacitance characteristic because the metamorphic layer of grinding has good obstructive ability. They reveal that grinding improves the surface corrosion resistance of workpiece. Then the mechanism of the corrosion resistance of grinding is revealed. The special grain boundary formed in grinding with much C element, large clusters and complex shape prolongs the corrosion channel, which reduces the corrosive speed. While, the sensitive hardening structure generated in grinding hardening with much free energy is easy to form the corrosion cell, which will accelerate the corrosion. [ABSTRACT FROM AUTHOR]

Symmetric and three asymmetric Σ5 tilt grain boundaries in niobium were studied by computer-aided modeling methods. The structure and energy of considered boundaries and the formation energy of point defects in them were calculated by molecular static modeling. The dependences of the formation energy of point defects on the distance from the plane of grain boundary were analyzed. The grain-boundary self-diffusion coefficients were calculated for the considered boundaries by the molecular dynamics method. [ABSTRACT FROM AUTHOR]

The effect of Mn on duplex stainless steel is of great importance in the development of lean duplex stainless steel. In this paper, we applied molecular dynamics simulations to quantitatively investigate the effect of Mn addition on the tensile behavior of ferritic/austenitic (bcc–fcc) iron duplexes as a model system for duplex stainless steels. We found that dislocations originate at grain boundaries and most of the initial dislocations in the grain boundaries are Shockley partial dislocations. The temperature and the number of dislocations conform to a normal distribution relationship. In addition, the tensile deformation mechanism of duplex stainless steel is dominated by both phase transformation and dislocation activity. Mn can improve the tensile properties of the material by delaying the arrival of plastic deformation, increasing the dislocation density to improve the strength of the model, and promoting the phase transformation mechanism of fcc → hcp → bcc. [ABSTRACT FROM AUTHOR]

Stainless-steel bipolar plates (BPPs) are of great significance in low-cost, easily processable, lightweight proton exchange membrane fuel cells (PEMFCs) despite the challenge presented by corrosion in protective coatings. Localized corrosion along the grain boundaries in a crystal film is common, but few preventive measures have been developed so far. Thus, we propose a novel strategy using a tantalum (Ta) and carbon (C) co-modification to improve the chemical stability of titanium carbide (TiC)-based coatings (Cr/Ta/TiC/C). During the film growth, the subjacent Ta atoms were thermally diffused throughout the columnar structure of TiC and reacted with the C layer. The reaction product, i.e., TaC, acted as a chemical passivator to the grain boundary. Combined with the C capping layer, these functional layers synergistically suppressed any localized corrosion. Therefore, corrosion current densities within the United States Department of Energy's technical recommendations were achieved in both potentiostatic and potentiodynamic polarization. Meanwhile, by controlling the Ta metal dispersion, the interfacial contact resistance between the multilayer structure and the carbon paper can be reduced to 7.1 mΩ·cm−2 at a compaction force of 140 N·cm−2. The substantial improvement in the corrosion resistance and conductivity of BPP places our work among the most efficient anticorrosion systems in PEMFC applications reported so far. [ABSTRACT FROM AUTHOR]

The paper studies the wetting of grain boundary triple junctions (GB TJs) by the second solid phase (intermetallic) δ in the Cu–In alloys. In this system, the portion of grain boundaries in a copper-based solid solution (Cu), which are "wetted" by the second solid phase δ, changes non-monotonically with increasing temperature. At first, the portion of such completely wetted GBs increases from zero to almost 100% when the sample is heated, and then quickly falls back to zero. The condition of complete wetting for the GB TJs (σGB > 1.73 σSS) is less stringent than for the GBs (σGB > 2 σSS). Therefore, if the transition from incomplete to complete wetting occurs with an increase in temperature, then all GB TJs should become completely wetted at a temperature TWTJ, lower than the temperature TWGB, at which all GBs become completely wetted. In this work on the Cu–In system, it was found experimentally for the first time that the wetting of the GB TJs also behaves non-monotonously. The percentage of wetted GB TJs also increases to 100% at first and then falls with increasing temperature. In this case, the portion of wetted GB TJs exceeds the portion of wetted GBs not only when it increases with increasing temperature, but also then, with the subsequent disappearance of fully wetted GBs. Grain boundary triple junctions in (Cu-In) solid solution are "wetted" by the δ intermetallic in broader temperature interval than grain boundaries. [ABSTRACT FROM AUTHOR]

In order to improve the microstructure of AZ31 magnesium alloy sheets and enhance their comprehensive mechanical properties, the effects of cryogenic treatment on the microstructure and mechanical properties after hot-rolled AZ31 magnesium alloy were investigated in this paper by combining different rolling reduction with cryogenic treatment. The results show that fine dynamic recrystallization grains appear at the original grain boundaries, and the grain becomes fine and uniform after rolling and deformation. After cryogenic treatment of the hot-rolled sheets, the grains are further significantly refined, the size tends to be homogeneous, the second phase is precipitated along the grain boundaries, and a small amount of twins are produced. In addition, after 20-min cryogenic treatment, the plasticity of the rolled sheets with 30% reduction was greatly improved, and the elongation at break was up to 14.2%, which was 55% higher than that of the original sheet; its hardness and tensile strength were increased from 64.4 HV and 230 MPa of the original sheet to 76.6 HV and 286 MPa, respectively, which shows that the cryogenic treatment of the hot-rolled sheets could effectively improve mechanical properties. This study provides some theoretical guidance and technical support for the processing and manufacturing of high-performance AZ31 magnesium alloy sheets, which has important academic significance and engineering value. [ABSTRACT FROM AUTHOR]

In this paper, the combined magnetic-vibration treatment purposed to reduce residual stress is evaluated. In combination with the single magnetic and vibration treatment, a comparison is performed after stress reduction in terms of the reduction effect, macroscopic properties, and metal properties of the material. According to the experimental results, different treatment methods can reduce the residual stress. Besides, the longitudinal residual stress was reduced more significantly than the transverse residual stress, and the combined magnetic-vibration treatment performed significantly better in reducing residual stress than either vibration or magnetic alone. After the adjustment of different treatments, the tensile strength showed a slight reduction, but the elongation was improved, with the mechanical properties reaching the optimum level after the combined magnetic-vibration treatment. The conductivity was improved, and the combined magnetic-vibration treatment led to a significant improvement. After the vibration and magnetic treatment were adjusted, the hardness was basically unchanged, despite a significant improvement of hardness after the combined magnetic-vibration treatment. The magnetic performance was improved after the adjustment of different treatment, and the combined magnetic-vibration treatment led to a significant improvement. The metallographic results show that the reduction of precipitated phases and the narrowing of grain boundaries caused by using different control methods may be the main influencing factors in the properties of the material. Moreover, after the combined magnetic-vibration treatment, there were more significant changes in the reduction of precipitated phases and the narrowing of grain boundaries. [ABSTRACT FROM AUTHOR]

In this paper, the influence of thermal aging on the microstructure and mechanical properties of reduced activated ferritic/martensitic is investigated in air at 550 °C for 5000 h. The microstructure evolution and precipitated phases following thermal aging are investigated via optical microscopy, scanning electron microscopy, and transmission electron microscopy. The tensile and impact properties are tested at different temperatures. The results indicate that the alloy microstructure exhibits good stability during aging. Yttrium has little effect on the evolution of Laves phases and carbides. Laves phases preferentially nucleate at the original austenite grain boundary, and the growth mechanism is diffusion-controlled. After aging for 5000 h, the growth rate of M23C6 decreases to about 75%, and that of MX decreases to about 85%. Moreover, the yield strengths of A (without Y) and B (with Y) Steels are 550 and 587 MPa at room temperature and 289 and 307 MPa at 650 °C, respectively. The alloys have good mechanical properties at both room and high temperatures. The ductile–brittle transition temperatures of A and B Steels are increased to − 60 and − 63 °C, respectively. Grain coarsening is the main causative factor for the decrease in alloy toughness. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization (DRX) plays an important role in microstructure evolution during hot deformation. In this paper, the hot deformation behavior and DRX mechanism of 7075 aluminum alloy were investigated by hot compression tests at a temperature of 250-450 °C and strain rate of 0.01-10 s−1. The experimental results show that the DRX is the main softening mechanism of the AA7075, and the relationships among temperature, strain rate and Z parameter were established. Besides that, the recrystallization fraction and grain size increase with the rising of temperature (250-450 °C) due to the accelerating of the grain boundary migration and movement. As the values of Z parameters increase, three typical softening mechanisms occur, ranging from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX). The characteristic of DDRX is mainly grain boundary (GB) bulging relying on GB migration. With regard to the situation of CDRX, the transformation of low angle grain boundary to high angle grain boundary due to the rearrangement of dislocation could be observed based on the electron backscatter diffraction analysis. The mechanism of CDRX and DDRX existed simultaneously in condition of moderate Z parameter. [ABSTRACT FROM AUTHOR]

The growth of graphene on Ni magnetic films is of great significance for graphene spintronics, whereas the existence of grain boundaries and twin crystal structures in Ni films is an obstacle for obtaining the large-scale and uniform graphene. In this paper, an epitaxial wafer-scale single-crystalline Ni(111) film with the flat and clean surface was successfully prepared on the commercial α-Al2O3(0001) substrate by a two-step method, which was demonstrated with several characterization methods. According to the abnormal grain growth mechanism, the clean and uniform sapphire surface plays a key role for the single crystallization of Ni films as it induces a weak interface energy difference between two atomic stacking structures (ABC and ACB), thus stimulating the evolution of Ni films from (111) out-of-plane textures to single crystals. Furthermore, an ultra-flat and wrinkle-free graphene monolayer was synthesized on the prepared Ni film, which further verified its high quality and effectiveness. [ABSTRACT FROM AUTHOR]

The stress relaxation (SR) test during plastic deformation is a useful technique for studying deformation processes. SR tests were performed during plastic deformation of pure magnesium, magnesium alloys and magnesium alloys-based composites over a wide temperature interval from room temperature up to 300 °C. Various theoretical approaches were applied for the estimation of characteristic parameters of thermally activated processes and finding of stress components. The aim of this study was to reveal the main features of deformation processes in hexagonal close-packed magnesium alloys and composites. The role of solute atoms in dynamic strain aging phenomena is discussed. In ultrafine-grained magnesium, grain boundary sliding during the stress relaxation tests was observed. The paper analyzes extensive set of results obtained by authors on cast and processed magnesium materials. [ABSTRACT FROM AUTHOR]

In the paper, we study the evolution of the structural phase state, deformation behavior, and fracture of ultrafine-grained near-β titanium alloy Ti–5Al–5Mo–5V–1Cr–1Fe after annealing in the temperature range 773–1073 K (0.4–0.55 Tm). The duration of the strain-hardening stage under tensile conditions is shown to be almost independent of the annealing temperature. The character of the strain-softening stage is largely determined by the alloy structure formed after annealing. It is found that annealing at the temperatures 773 and 873 K does not change the deformation behavior of the ultrafine-grained alloy under tension at room temperature. Deformation and fracture of the specimens localize in shear bands. Recrystallization occurring at the annealing temperature 973 and 1073 K leads to the transition of grain boundaries to a more equilibrium state and to a sharp decrease in strength and softening rate of the titanium alloy. It also affects the neck formation prior to fracture, giving a developed neck. Fracture surfaces are indicative of ductile dimple fracture of the alloy in all states. The dimple size depends on the size of structural elements after heat treatments. Based on the experimental data, the σ0 value and Hall–Petch coefficient k are determined. In the investigated grain size range (0.17–1.25 μm) the values are found to be, respectively, 680 MPa and 0.36 MPa m1/2. [ABSTRACT FROM AUTHOR]

Scientific understanding of the behavior of wrought magnesium alloys is quite mature, with literally thousands of papers published on the topic, along with several reviews. Most of this research is relatively recent, being published after the year 2000. With such a large body of work available to the reader, it could easily be missed that the field of magnesium metallurgy is poised for significant advances. Access to synchrotron and neutron scattering has revealed new knowledge about deformation and fracture behavior, and the complex interaction between solutes, dislocations, interfaces, and disconnections is only just becoming clear. Supercomputing now makes it possible to use atomic-scale simulation techniques to make material calculations such as stacking fault energy predictions, and the simulation of atom-by-atom movement at boundaries and twins in three dimensions is now feasible. Advanced microscopy techniques such as atom probe tomography are allowing us to examine the complex chemical nature of grain boundaries on the nanoscale. These are just some of the areas ripe with potential for new discovery. With so much information available to the reader, it can be difficult to identify those areas of study in which the greatest knowledge gaps exist or those which are most ripe for exploration. For this reason, several authors have teamed up to write this short discussion piece which highlights research areas which the authors agree have the most potential for impact in the field. [ABSTRACT FROM AUTHOR]

Electrical conductivity/resistivity of elemental fcc metals, such as Al and Cu, has been investigated intensively for decades, both theoretically and experimentally. Since these metals are of great practical importance for electrical wiring, reducing their resistivity even by a few percent may have very strong impact on their application effectiveness. In this paper, we report on electrical resistivity measurements in Al single crystals grown by the Bridgman method. We found that their resistivity at room temperature decreases by 11.5% upon heat treatment in a boron environment at 600 °C, i.e., well below the melting temperature of Al (Tm = 660 °C). The residual resistivity indeed reaches its lower limit dictated by electron–phonon interaction at room temperature. We explain this effect by the boron-induced formation of distorted regions at the surface of the Al crystals. These regions are 30–50 μm in size and comprise finer grains with an average size of 5 μm, separated by low-angle grain boundaries. Resistivity reduction is mainly due to the getter effect, i.e., the removal of the impurity atoms from the crystal bulk by the outward diffusion to the distorted surface regions. [ABSTRACT FROM AUTHOR]

In this paper, we resolve the role of grain boundaries on toughness and the brittle-to-ductile transition. On the one hand, grain boundaries are obstacles for dislocation glide. On the other hand, the intersection points of grain boundaries with the crack front are assumed to be preferred dislocation nucleation sites. Here, we will show that the single contributions of grain boundaries (obstacles vs. source) on toughness and the brittle-to-ductile transition are contradicting, and we will weight the single contributions by performing carefully designed numerical experiments by means of two-dimensional discrete dislocation dynamics modelling. In our parameter studies, we vary the following parameters: (i) the mean free path for dislocation glide, δ, combined with (ii) the (obstacle) force of the grain boundary, ϕ, and (iii) the dislocation source spacing along the crack front, λ. Our results show that for materials or microstructures for which the mean distance of the intersection points of grain boundaries with the crack front is the relevant measure for λ, a decrease of grain size results in an increase of toughness. The positive impact of grain boundaries outweighs the negative consequences of dislocation blocking. Furthermore, our results explain the evolving anisotropy of toughness in cold-worked metals and give further insight into the question of why the grain-size-dependent fracture toughness passes through a minimum (and the brittle-to-ductile transition temperature passes through a maximum) at an intermediate grain size. Finally, a relation of the grain-size-dependence of fracture toughness in the form of K(dδ, dλ) = KIC + kdδ0.5/dλ is deduced. [ABSTRACT FROM AUTHOR]

Shear-coupled grain boundary migration (SCGBM) has already been observed in extensive experiments and serves as an effective mechanism for the grain growth in nanocrystalline materials. Meanwhile, it is well known that precipitates strongly inhibit the motion of GBs. However, the effect of precipitates on SCGBM is not clear. In this paper, a theoretical model is established to investigate the role of precipitates on SCGBM. The effects of the characteristics of the precipitate and the GB are studied in detail. It is found that precipitates can significantly inhibit SCGBM. Interesting, the results show that the pinning effect exerted by precipitates on SCGBM is strongly relevant to their positions. Moreover, the resistance for SCGBM hindered by precipitates can be controlled by tailoring the characteristics of both the precipitates and GBs. In addition, it is discussed that a possible recrystallization occurs when the GB is hindered and it is found that the SCGBM process also facilitates it. [ABSTRACT FROM AUTHOR]

Recently (Prokofjev in J Mater Sci 52:4265–4277, 2017. 10.1007/s10853-016-0681-2), the empirical expressions representing the surface tension of general-type high-angle grain boundaries in elemental solids as a function of their melting temperature and molar volume in the solid state at the melting temperature were proposed. In this paper, the application of the expressions to estimate the grain boundary surface tension in the allotropes of elemental solid, which do not melt but transform to the higher-temperature allotrope, is described. The parameters of the temperature dependences of grain boundary surface tension in allotropes of 22 elemental solids are presented. [ABSTRACT FROM AUTHOR]

The present paper has focused on improving strength and elongation of AA 1050 alloy via equal channel angular pressing (ECAP), intermediate annealing and post-rolling process. At the first and second ECAP passes, the ideal shear texture component has been developed while by proceeding ECAP passes (n = 3, 4), the intensity of texture component has been weakened. In the following, as a result of intermediate annealing at 150 °C, cube texture component ({001}<110>) was developed in the alloy. Then during post-rolling process, the prior texture component disappeared and the augmentation of copper-type texture component ({110}<112>) has been observed. The first and second ECAP passes lead to increase in ultimate tensile strength at the expense of considerable decrease in elongation and work hardening capacity. However, during third and fourth ECAP passes, the homogenous microstructure with fine equiaxed grain is achieved, also intermediate annealing at 150 and 225 °C and 50-75% rolling reduction attributed to high angle grain boundaries (HAGBs) promotion. Eventually, an appropriate balance of strength, elongation and work hardening capacity of AA 1050 alloy is obtained via ECAP (n = 3, 4), intermediate annealing (T = 150, 225 °C) and post-rolling (r = 50-75%). [ABSTRACT FROM AUTHOR]

This paper presents the effect of a new processing technique called hard cyclic viscoplastic deformations (HCVD) on the enhancement of mechanical and electrical properties in a copper-chromium alloy. A modern severe plastic deformations (SPD) technique named "Indirect Extrusion Angular Pressing" (IEAP) was also implemented to refine the microstructure before HCVD. Samples were processed by IEAP, HCVD, and IEAP followed by HCVD, and the evolution of microstructure, mechanical properties, and electrical conductivity was analyzed. Results of materials characterization revealed that HCVD dissolved the Cr particles, reduced the microstrains, and transformed the elongated microstructure to an equiaxed structure in the SPD-induced copper. Results of mechanical testing showed that HCVD enhanced the elongation of SPD-processed samples at the cost of a slight decrease in strength and hardness. Further, aging treatment at different temperatures was conducted on the samples. Results showed that HCVD-processed samples retained the dislocation densities in the microstructure and possessed the highest hardness and electrical conductivity after aging. Such enhancement was attributed to the effect of HCVD on the relaxation of severely deformed grain boundaries as well as the contribution of HCVD to the full dissolution of Cr residuals, and subsequently, the formation of Cr sub-precipitates after aging. [ABSTRACT FROM AUTHOR]

This paper reports on the optimized parameters of the rolling reduction (RR) and aging treatment (AT) of Fe-Si-Mn aluminum sheets with the aim of reducing the anisotropy and improving the deep drawing performance of the material. Results show that with an increase in the RR, the ultimate tensile strength increases while the elongation decreases. As a result of this treatment, the proportion of Cube texture and Copper texture in specimens is found to decrease gradually and transform into the Brass texture. The transition sequence of texture is found to be Cube→Goss→Brass along the α-orientation line, and the transition path of the Copper texture is found to be Copper→S→Brass along the β-orientation line. The aluminum alloy exhibits the minimum anisotropy (IPA% = 8.74%) and the best deep drawing performance (an Erichsen number of 7.51) obtained in this work when the RR was 29.4%. Subsequently, the AT can effectively reduce the density of dislocations near the grain boundaries and further improve the Erichsen number (from 7.14 to 8.01, an increase of 12.2%). Our results demonstrate that the deep drawing performance of Fe-Si-Mn aluminum sheets can be enhanced effectively via RR and AT; this work provides a design strategy for improving the fracture consistency of the Fe-Si-Mn aluminum alloy. [ABSTRACT FROM AUTHOR]