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Abstract In this work, the effect of equal channel angular pressing (ECAP) on the microstructure and mechanical properties of zinc and zinc alloys with Ag, Cu, and Mn additions (0.5 at%) was investigated. Four passes of ECAP Route B C was performed at room temperature for each material. Properties of investigated materials after ECAP were compared to their coarse grained counterparts obtained via indirect hot extrusion at 300 °C. Highest strengthening effect was observed for alloy containing the Mn addition. Grain refinement in materials after ECAP was obtained, mean grain diameter is equal to 20 µm in the case of pure zinc, and less than 3.2 µm for alloys. Strain rate dependent plasticity increase was observed for all fine grained materials, with maximum elongation of 510% measured for Zn-Cu alloy after ECAP. Grain refinement did not result in increased yield and ultimate tensile strength of alloys after ECAP. In all investigated materials tensile properties after ECAP were 20 ~ 60% lower than in hot extruded samples. Based on the tensile properties, microstructure and texture analysis, the changes in the main deformation mechanisms were considered. It was presented that the crystallographic texture and grain size are the main factors affecting twinning, slip and non-slip deformation mechanisms resulting in large differences in observed mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract The pre-mixed pure Ti and Cr 2 O 3 powder was consolidated by spark plasma sintering (SPS) and hot extrusion to fabricate α-titanium (Ti) materials with oxygen (O) and chromium (Cr) elements by powder metallurgy (PM) process. The Cr 2 O 3 particles were completely decomposed during SPS, and then O and Cr atoms were dissolved in α-Ti matrix. Oxygen atoms were remarkably improved the mechanical strength of PM Ti-O-Cr alloys by their solid solution hardening effect. The Cr solution and Ti 4 Cr precipitates had important roles to obstruct the grains coarsening behavior by the solute drag and Zener pinning effects, respectively. The solid solution strengthening effect by Cr atoms, however, was very limited due to a small Cr solubility of about 0.35 at% in α-Ti phase of Ti-O-Cr alloys. Since Ti 4 Cr precipitates with 10–20 µm diameters were not so fine, they hardly contributed to the precipitation hardening of Ti-O-Cr alloys. [ABSTRACT FROM AUTHOR]

Abstract The present article presents the effect of Sc addition on the secondary dendritic arm spacing, eutectic Si modification, intermetallic phase modification, aging behavior and subsequently the mechanical behavior in A356-5TiB 2 in-situ composite. The A356-5TiB 2 in-situ composite showed a 40% reduction in SDAS compared with A356 alloy, whereas addition of 0.4 wt% Sc and 5 wt% TiB 2 in A356 alloy resulted in a 65% reduction in SDAS. The eutectic Si in A356-5TiB 2 composite had a plate like morphology similar to A356 alloy but showed a reduction in length, whereas the addition of Sc resulted in a fibrous and particulate morphology of eutectic Si. The needle like β-Al 5 FeSi phase in A356-5TiB 2 composite changed to Al 5 Fe(Si,Sc) phase having smaller size and irregular morphology with the addition of Sc. The intermetallic phase formation and phase modification was confirmed and characterized using X-ray diffraction, Transmission electron microscopy - Energy dispersive spectroscopy and Scanning electron microscopy. Addition of Sc to A356-5TiB 2 in-situ composite resulted in improved mechanical properties. Further, T6 heat treatment revealed a significant improvement in mechanical properties for A356-5TiB 2 in-situ composite with and without Sc addition. [ABSTRACT FROM AUTHOR]

Abstract Previous studies have revealed that the shear band propagation of metallic glasses can be strongly influenced by decreasing the sample size, leading to the dramatically enhanced plasticity. Here we show that the sample size also affects the shear band fracture behavior. When reducing the sample size, the compressive shear band fracture mode is changed from the typical instant fracture with vein patterns into a gradual fracture mode without the formation of vein pattern. This can be explained by the marked reduction of energy dissipation density during shear band sliding in small samples and thus the enhanced shear band stability against the instable fracture. [ABSTRACT FROM AUTHOR]

Abstract Trace amounts of inoculants - germanium (0.02 at%), indium (0.02 at%) or tin (0.01 at%) - were added to a ternary Al-0.06Sc-0.06Zr at% alloy to study their effects on Al 3 (Sc,Zr) precipitation. During isothermal aging at 300 °C, the In- and Sn-containing alloys exhibit an early microhardness increases, which is attributed to In or Sn clustering. Peak isothermal microhardness due to Al 3 (Sc,Zr) precipitation is achieved simultaneously (~4 h) for the three inoculated alloys and an inoculant-free alloy. Isochronal aging produces a low-temperature microhardening response for the In- and Sn-containing alloys, followed by two microhardness peaks at 350 and 450 °C for all four alloys, associated with precipitation of Sc and Zr, respectively. Atom-probe tomography demonstrates partitioning of Ge and Sn (up to 0.5 at%) from the matrix to the Al 3 (Sc,Zr) precipitates, with partitioning to Sc-rich precipitate cores (for isothermal aging) or to both Sc-rich cores and Zr-rich shells (for isochronal aging). Inoculant partitioning at precipitate cores and early low-temperature microhardness increases are consistent with inoculant clustering to form nucleation sites for Sc and Zr precipitation. Inoculant segregation at the precipitate shells can be explained by co-precipitation of the fast-diffusing inoculant element and the slow-diffusing Zr, between which an attractive binding energy exists. When compared to the inoculant-free control alloy with a somewhat higher Sc content, the three inoculated alloys exhibit a 2- to 10-fold decrease in creep rates at 300 °C for stresses above ~18 MPa, but a small reduction in creep threshold stresses from 12 to ~10 MPa. [ABSTRACT FROM AUTHOR]

Abstract Stir tools with different pin eccentricities were applied to the friction stir processing of Al-5052 alloy. Results show that pin eccentricity enhances material flow and refines grains of stir zone. The stir zone produced by a stir tool with 0.4 mm pin eccentricity performs the highest hardness and yield strength, attributing to the enhanced grain-boundary strengthening. [ABSTRACT FROM AUTHOR]

Abstract Microstructure of deformed DMLS-AlSi10Mg under quasi-static loading was studied using TEM to elaborate the strengthening mechanisms. In addition to Orowan (due to presence of Si precipitates), Hall-Petch (due to eutectic Si walls), and dislocation hardening (due to pre-existing entangled dislocations) mechanisms, Mg 2 Si precipitates (colonies) contributed to the strength of alloy by impeding dislocation motion. The level of this contribution was evaluated as ~13 MPa by comparing the modeled and measured yield strength. [ABSTRACT FROM AUTHOR]

Abstract The effect of textures and microstructure topologies on mechanical property evolution and tensile crack propagation behavior during uniaxial tension was systematically investigated. Results show that β-fiber textures are formed in AA7021 alloy for regular rolling and alternate rolling, respectively. While under transverse rolling the sample is mainly occupied by Copper texture components. In addition, on a macro scale, Copper texture components with low Schmid factor (hard orientation) are responsible for the higher yield strength compared to other texture components, and the significant elongation for the alternate rolling plates is attributable to the least square error of the grain size. On a micro scale, the way to improve crack deflections (tensile crack resistance) during uniaxial tension tests mainly involves two steps: intensifying Goss etc. high twist angle boundary components and decreasing residual compressive stress which aims to generate secondary cracks easily. Furthermore, there is no evidence that tensile crack deflections are relevant to tilt angle boundaries during uniaxial tension tests. Moreover, in the condition of transverse rolling, it is indicated that Brass grains with 8 movable slip systems can effectively facilitate intracrystalline extension for secondary cracks B and C, however, as to Copper, the secondary crack A only propagates along the boundaries because of the less 6 movable slip systems. [ABSTRACT FROM AUTHOR]

Abstract Laser powder bed fusion additive manufacturing (L-PBF AM) offers great potential for local microstructure control. During this process, solidification occurs in conditions that are far from equilibrium and possesses – in the majority of cases – a strong directionality. In general, the size and morphology of the resulting microstructure is a function of two well-known parameters: the temperature gradient within the liquid phase (G) and the velocity of the solidification front (R). To provide guidance in selecting appropriate, systematically defined, process parameters for L-PBF of 316L stainless steel square pillars, we developed an intentionally simple thermal model to express these two parameters, G and R, as a function of selected process variables (laser scan speed, laser power) and material properties (thermal diffusivity). Results from both microstructural and mechanical characterization of the pillars indicate that high-strength, fully-dense parts with a highly oriented cellular microstructure can be obtained when using significantly different sets of process parameters. Furthermore, despite its simplicity, the numerical model correlates well with experimental evidence and confirms that rather than creating variable microstructures, the process parameter constraints actually lead to a stable cellular microstructure regardless of the wide process window studied. [ABSTRACT FROM AUTHOR]

Abstract Thermomechanical processing determines the practical applications of metal–matrix composites (MMCs) by contributing to the interrelationship between their microstructure and properties. In this study, we investigate the changes in Al-3.0Cu-1.2Mg/SiC p (40 vol%) caused by the tension applied at high temperatures and strain rates. The study shows the microstructural changes and mechanical characteristics resulting from the cold/warm and hot rolling of the extruded material. It is observed that hot rolling has a favorable effect on the restoration of the defects formed in parts of the extruded bar. The microstructural characteristics of the composite related to the deformation-induced redistribution of the secondary inclusions in the matrix and fracture of the reinforcement particles are shown. High-temperature uniaxial tensile testing of the studied composite conducted under high strain rates (10−1 and 10−2 s−1) indicates an increase in the ductility. The decrease in the stress of the tested samples is attributed to the refined grains in the matrix after the thermomechanical processing. The testing of the given material provides the stress–strain relationships, which indirectly assist in ranking the relative formabilities of the differently processed sheets of the MMCs with a high-volume fraction of the reinforcement particles. The proposed approach may be considered for the near net-shaped manufacturing of MMCs with high wear resistance and low thermal expansion coefficients. [ABSTRACT FROM AUTHOR]

Abstract The effects of hydrogen charging on the evolution of strain-induced lattice defects and phase transformation were investigated in 316L stainless steel. The initial material was obtained by cold rolling to a thickness reduction of 20%. The surfaces of some of the initial samples were cathodically charged with hydrogen. Afterward, both the charged and uncharged samples were subjected to tension until failure. The dislocation density and twin-fault probability in the charged and uncharged specimens during tension were compared. We found that hydrogen charging reduced the degree of increase in the dislocation density and twin-fault probability during the application of tension to the same strain level. Significant martensitic phase transformation was observed in the uncharged samples tested to the strain of 10% or higher. In the hydrogen-charged samples, only a slight increase in the martensite phase fraction was detected. A correlation between the α′-martensite fraction and the dislocation density was found for the studied samples, suggesting that the lower degree of martensitic phase transformation in the charged 316L steel was caused by the smaller amount of stress developed due to the lower dislocation density. In accordance with the differences observed in the phase composition and defect densities, the hydrogen-charged material exhibited lower surface hardness. [ABSTRACT FROM AUTHOR]

Abstract Selective laser melting, due to the high energy density input and the small interaction time (106 K/s), can result in an ultrafine microstructure and excellent mechanical properties. However, due to the nonuniform nature of the temperature distribution and the transition from liquid to solid, high residual stresses exist. High residual stresses in the parts can increase the risk of material distortion and cause many problems, such as dimensional inaccuracy or cracks. This work systematically investigated the influence of annealing on the microstructure and mechanical properties of SLM-processed AlSi7Mg alloy parts. The residual stresses relaxed significantly after annealing. The Vickers hardness and the tensile stress greatly reduced, while the elongation increased. The fracture mode of the as-fabricated sample was ductile and brittle mixed fracture, whereas the fracture morphology of the annealed sample presented many more dimples, and the elongation also increased, which indicated the ductile mode. [ABSTRACT FROM AUTHOR]

Abstract Revealing the microstructural parameters-mechanical properties relationship is very critical for the microstructure tailoring and properties optimization of titanium alloy. In this work, the dependence of mechanical properties on microstructural parameters of TA15 titanium alloy with tri-modal microstructure was investigated. The results indicate that at a certain lamellar α (α l) content (28%), both of yield strength (σ 0.2) and ultimate tensile strength (σ b) decrease continuously with the increase of equiaxed α (α p) content, while the decrease speed slows down at higher α p content. At a certain content of α p of 20%, σ 0.2 and σ b both increase first and then decrease as the content of α l increases. The above effect laws result from the competition between the softening effect caused by increasing the softer α p and α l contents and the strengthening effect relating to α l /β t interfaces and β t hardening. As for the elongation (δ) and reduction of area (Φ), they show an increase trend with α p content increasing at a certain α l content of 28%. However, they decrease first and then increase with α l content increasing at a certain α p content of 20%. The early plasticity decrease at lower α l content is due to the popular rapid void nucleation and cleavage fracture along α l /β t interfaces. When α p or α l content increases to higher level, the deformation compatibility and homogeneity improves, which suppress the rapid void nucleation and cleavage fracture along α l /β t interfaces. Meanwhile, the fracture mechanism changes from the coexistence of void coalescence and cleavage fracture to the void coalescence dominated fracture, thus the plasticity increases. Moreover, a back-propagation neural network model was developed to correlate the mechanical properties with microstructural parameters of tri-modal microstructure. The prediction results suggest that better combination of strength and plasticity can be achieved by controlling the contents of α p and α l in the range of 10–15% and 22–27%, respectively. [ABSTRACT FROM AUTHOR]

Abstract Al99.5 and AlSi12 matrix syntactic foams were produced by pressure infiltration of Globocer grade ceramic hollow spheres. The produced aluminium matrix syntactic foams (AMSFs) were investigated by compressive tests, dynamic mechanical analysis (DMA), finite element methods (DMA) and elasticity based analytical calculations. The aim of the investigations was (i) to map the compressive properties of the AMSFs, (ii) to determine and compare the effective Young's modulus of the AMSFs determined by compressive tests, DMA, FEM and analytical calculations and (iii) to determine the low frequency damping capability of the AMSFs. The compressive tests showed pronounced differences between the two matrix materials, characterized by higher compressive strength, compressive strain and absorbed mechanical energy in the case of AlSi12 matrix, however, the energy absorption efficiency due to the different failure mechanism of AMSFs (homogeneous densification in the case of Al99.5 and cleavage in the case of AlSi12 matrix, respectively). The DMA tests confirmed the effective Young's moduli values, measured by compression and proved higher damping capability in the case of AlSi12 matrix. FEM and analytical calculations also confirmed the measured effective Young's moduli within a reasonable error band. [ABSTRACT FROM AUTHOR]

Abstract We present a series of in-situ synchrotron X-ray diffraction deformation experiments conducted on polycrystalline AZ31 Mg alloy in a D-DIA apparatus at temperatures ranging from 154 °C to 286 °C, at ~3.1 GPa confining pressure and a strain rate of 5 × 10−6/s. For each experiment, we fit the X-ray diffraction data using elastic plastic self-consistent (EPSC) models that incorporate an isotropic deformation mechanism in addition to basal, prismatic and pyramidal slip systems. From the EPSC models, we report the sample strength and the critical resolved shear stresses (CRSS) for individual slip systems for each experiment and compared with previously reported data on this material. [ABSTRACT FROM AUTHOR]

Abstract Nanotwinned nanocrystalline CoCrFeNi high-entropy alloy films were prepared by magnetron sputtering. A disordered face-centered cubic structure was identified, with a uniform distribution of chemical elements. Both <1 1 0> out-of-plane and <1 1 1> in-plane textures were also observed in the nanotwinned film with a thickness of 2.98 µm. The fatigue resistance of the films was analyzed by nanoindentation technique with up to 103 cycles under various impact energies, complemented by post-test atomic force microscopy investigation of indentation craters. Unlike coarse-grained samples, the nanotwinned films exhibited excellent fatigue resistance, characterized by history-independent and near-stable fatigue responses. Under the influence of the textures developed in the films, the nanotwin planes were oriented toward the loading direction under each fatigue cycle. As such, extremely stable correlated necklace dislocations structure formed and moved back and forth along the twin boundaries during cyclic loading, which preserved the slip systems as well as the coherency and stability of twin boundaries. [ABSTRACT FROM AUTHOR]

Abstract A severe plastic deformation is widely used to improve the mechanical properties of non-heat-treatable alloys. Thus, the investigation and modeling of microstructural evolutions of materials during large straining are of great importance. In this research, substructural evolutions of four different kinds of Al alloys namely Al-1Mn, Al-1Mg, Al-2.77Mg and Al-5Mg, have been studied using a dislocation based model and the mechanical properties of these alloys have been compared considering all microstructural parameters such as dislocation density, subgrain size, cell wall misorientation and the effect of alloying element. As a result, a simplified general equation has been expressed in order to predict the flow stress of aluminum alloys after large plastic deformation based on the influence of substructural parameters. Using this model, it is shown that magnesium is more effective to improve the strength of aluminum than manganese as an alloying element. In addition, due to higher SFE, Al-Mg alloys have more hardening rate with finer grains, accordingly. [ABSTRACT FROM AUTHOR]

Commercially pure Ti grade 2 was multi-directionally forged (MDFed) at room temperature. MDFing could be successfully carried out without any cracking to a cumulative strain of ΣΔε = 2.0. Ultrafine-grained (UFGed) structure gradually developed with increasing cumulative strain mainly by mechanical twinning and kinking. An average grain size of approximately 400 nm was attained. The mechanical properties were drastically modified by the grain refinement and a superior balance of tensile strength and ductility, 710 MPa and 21%, was achieved. Additional cold rolling of the UFGed Ti possessed further better mechanical properties of 930 MPa tensile strength and 19% ductility. [ABSTRACT FROM AUTHOR]

A new standard is currently being developed under the auspices of ECISS/TC 101 WG1 for the small punch testing technique for the estimation of both tensile and creep properties. Annex G of the new standard is covering the assessment and evaluation of small punch creep (SPC) data. The main challenge for estimating uniaxial creep properties from SPC data is the force to equivalent stress conversion between SPC and uniaxial creep tests. In this work a range of SPC assessment methodologies, benchmarked for the standard, are compared for verifying the best practice used in the standard. The estimated equivalent stresses for SPC are compared to uniaxial creep stresses at equal rupture times, using three alternative models. In-depth analyses are performed on SPC and uniaxial creep data for P92, F92 and 316 L steel tested within an inter-laboratory round robin. The formulation for SPC equivalent creep strain rate in the standard is also assessed. [ABSTRACT FROM AUTHOR]

Proper mechanical stability in retained austenite is a crucial factor for medium Mn steel to attain high strength and excellent ductility. In this paper, intercritical annealing and quenching and partitioning (IA & Q&P) processes are applied to medium Mn steel, to obtain retained austenite with proper mechanical stability. The effect of intercritical annealing temperature on mechanical stability of retained austenite is studied using interrupted tests. Moreover, from the perspective of usage of medium Mn steel, the mechanical stability of retained austenite at uniaxial tension and plane strain states is further investigated, to understand the transformation of retained austenite. Results indicate that high intercritical annealing temperature (680 °C) caused the austenite to transform immediately, due to the limited resistance of austenite to martensite transformation, caused by low carbon (C) content. This low C content also led to low stacking-fault energy, which may be another way to promote the transformation of austenite. Additionally, due to the high Schmid factor, caused by enhanced grain rotation and strain state, the retained austenite has relatively low stability at the early stage of the plane strain state. With increasing martensite surrounding the austenite, the retained austenite achieves high mechanical stability at the later stage of the plane strain state. [ABSTRACT FROM AUTHOR]

In order to improve the plasticity of AlCoCrFeNi high entropy alloys (HEA) without obviously decreasing the strength, Co has been added to this alloy as Co is a FCC phase stabilizer. In this study, the alloying effects of Co addition on the phase types, microstructure and mechanical properties of (AlCoCrFeNi) 100- x Co x are investigated systematically. The result shows that Co element has the capacity to induce phase transformation from BCC phase to FCC phase in the (AlCoCrFeNi) 100- x Co x alloy system, and the volume fraction of FCC phase increases from 0% to 77% as the Co content increases. Compressive testing shows that Co addition has a positive effect in improving the plasticity of AlCoCrFeNi HEA, and the fracture strain increases gradually from 27% to 40%, while the ultimate strength only reduces from 2743 MPa to 2680 MPa as the Co content changes from 0 to 16 at%. The maximum ultimate compressive strength reaches 2974 MPa, while the fracture strain reaches 30%. The increased volume fraction of FCC phase is the main factor in the plasticity increases, and the valence electron concentration (VEC) increase induced by Co addition is the main factor in FCC phase volume fraction increases in this alloy. [ABSTRACT FROM AUTHOR]

Normal plate impact experiments were conducted to study the spall behavior of AMX602 magnesium alloy fabricated via Spinning Water Atomization Process (SWAP), which was followed by cold compaction and hot extrusion. Incipient spall damage in the specimens was measured at different shock conditions using 51 mm and 105 mm diameter bore gas guns. The Hugoniot Elastic Limit (HEL) was measured to be approximately 187 ± 11 MPa. The spall strengths extracted from the free surface velocity profiles of the shocked specimens was found to increase by 8% for shock stresses ranging from 1.61 to 4.53 GPa. The experimental data also revealed some inherent scatter in the spall strength data due to microstructural heterogeneity. Post-test fractographic analysis of the shock-recovered specimens suggests that the initiation of spall was most likely associated with intermetallic Al 2 Ca-bearing precipitates forming during the hot extrusion process. The subsequent spall failure propagated via cavitation events that involved the nucleation of nano- and micrometer-sized voids with very limited plastic growth. [ABSTRACT FROM AUTHOR]

The fatigue test of 6005A cold metal transfer welded joint were carried out at room temperature and crack initiation near pores was systematically revealed. The fatigue strength of welded joint at 5 × 10 6 cycles based on S-N curve can be estimated as half of yield strength, which can be predicted reliably in engineering application. The fatigue test showed welded zone is the weakest zone due to the existence of micropores defects in the surface of the joint, even if there is softening zone in HAZ which is shown in hardness curve. Thinking about the existence of micropores, stress concentration will be produced near the pore even in smaller cyclic stress, which will drop down the crack initiation threshold, and the cupped grain boundary inside the pore may aggravate this condition. The pore in the equiaxed crystal microstructure would produce microcrack more easily than in columnar crystal structure. Moreover, there will be cracks with short-haul near the pore in the sample which isn't failed. These cracks won't impact the fatigue life of sample. But the microcrack occur in each of pores will converge into a macrocrack, when more than two pores gather in one region, then the fatigue property of the joint will be affected, seriously. Therefore, pores should be avoided in the process welding aluminum alloy as much as possible, especially the gathering of multiple pores. [ABSTRACT FROM AUTHOR]

The present work aims to study the bake-hardening behaviour in dual-phase (DP) steels. The mechanical properties and BH-values in dependency of the BH-parameters were determined and related to specific microstructural features in order to characterize the age- and strain-hardening behaviour. Micromechanical modeling by means of representative volume element (RVE) approach was used to describe the effect of BH on the mechanical behaviour of DP steel numerically taking into account microstructural features. 2D RVEs were created based on real microstructures. The flow behaviour of single phases was modelled using a Taylor-type dislocation-based work-hardening approach. The volume change during austenite-to-martensite transformation was also modelled and the resulting prestrained areas in ferrite were considered to be the storage place of GNDs. Afterwards, prestraining of 2% and 5% were imposed on the RVEs through numerical uniaxial tensile test. Then, the BH annealing was implemented on the prestrained RVEs in order to investigate the strain partitioning during annealing. Subsequently, numerical tensile tests were implemented on the bake hardened RVEs in order to study the stress-strain distribution on the microstructures. Finally, the flow curves of simulations on BH-treated and conventional DP steels were compared with experimental results showing a good correlation between experiments and simulations. [ABSTRACT FROM AUTHOR]

Heat-to-heat variation of creep strength is significant in grade 91 (Gr.91) steel, but the causes of the variation have not been well understood yet. In the present paper, creep rupture data of 14 heats of Gr.91 steel were analyzed paying attention to their chemical compositions and microstructures. The longest creep rupture lives analyzed are 2 × 10 5 h at 500 and 550 °C and 10 5 h at 600 °C. The causes of the heat-to-heat variation are different, depending on creep test conditions. At low temperature and high stress (creep rupture life of 10 4 h at 500 and 550 °C), creep rupture strength increases with increase of hardness after tempering. This suggests strengthening by a fine subgrain microstructure developed during normalizing and subsequent tempering. At higher temperature and intermediate time range (10 4 h at 600 °C), creep rupture strength depends on Cr concentration of the heats in addition to the hardness. This finding suggests an important contribution of recovery process of the subgrain microstructures to creep strength of the steel. In long-term creep (2×10 5 h at 550 °C and 10 5 h at 600 °C) creep rupture strength primarily increases with increasing grain size of the heats. This suggests that grain boundary sliding is an important deformation mode at low strain rate because of fine grain size usual with Gr.91 steel. Specifications on Ni concentration and N% / Al% ratio are newly introduced in the type II version of Gr.91 steel. They are not effective to eliminate a heat with low creep strength. [ABSTRACT FROM AUTHOR]

During the Selective Laser Melting (SLM) process large temperature gradients can form, generating a mismatch in elastic deformation that can lead to high levels of residual stress within the additively manufactured metallic structure. Rapid melt pool solidification causes SLM processed Ti6Al4V to form a martensitic microstructure with a ductility generally lower than a hot working equivalent. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. The use of high temperature pre-heating during an SLM build can assist in reducing thermal gradients, enable a more controlled cooling with the possibility to control/tailor as-built mechanical properties. In this work a high temperature SLM powder bed capable of pre-heating to 800 °C is used during processing of Ti6Al4V feedstock. The effect of powder bed temperature on residual stress formation, microstructure and mechanical properties was investigated. It was found that increasing the bed temperature to 570 °C significantly reduced residual stress formation within components and enhanced yield strength and ductility. This pre-heating temperature enabled the decomposition of α ′ martensitic microstructure into an equilibrium α+β microstructure. At 570 °C the yield strength and elongation of components was improved by 3.2% and 66.2% respectively. [ABSTRACT FROM AUTHOR]

Conventional Ashby plots for material selection may not appropriately describe material properties at small-length scales, new plots taking account of size effects are urgently needed for micro- or nano-mechanical design. Here, I show strength–modulus, strength–density, and size effect–Peierls stress plots for various solid materials at small scales. [ABSTRACT FROM AUTHOR]

The tensile and high-cycle fatigue tests of Fe-30Mn-0.9C twinning-induced plasticity (TWIP) steel after 30%, 60% and 70% pre-straining were performed. Meanwhile, the surface damage morphologies of post-fatigue specimens and microstructure evolutions of pre-strained and post-fatigue pre-strained specimens were also investigated. It is found that the fatigue properties of the TWIP steel can be effectively improved through pre-straining, because the pre-straining can change the fatigue strength coefficient and exponent, respectively. The improvement of fatigue strength coefficient may be attributed to the strengthening mechanisms induced by both twin boundaries and dislocations; while the variation of fatigue strength exponent should be resulted from the combined effects of deformation homogeneity and slip reversibility, as well as the internal damages. Furthermore, the detailed mechanisms associated with the variations of fatigue strength coefficient and exponent were discussed. This study may enrich the fundamental knowledge about how to improve the high-cycle fatigue properties of TWIP steels. [ABSTRACT FROM AUTHOR]

The knowledge on constitutive mechanical behavior at the temperatures close to the solidus is essential for predicting high-temperature deformation and fracture, e.g. cold and hot cracking of aluminum alloys. In this work we studied the tensile mechanical properties of an as-cast AA7050 alloy in a near-solidus temperature regime. Tensile tests were carried out using Gleeble-3800™ system at temperatures from 400 to 465 °C and at strain rates from 0.0005 to 0.05 s −1 . The results show that the strength decreases with increasing temperature and decreasing strain rate. Meanwhile, ductility decreases with the increase of temperature and strain rate. The constitutive parameters were extracted by fitting the test data to the extended-Ludwik and creep-law equations. The parameters for the extended-Ludwik equation are continuous with the values from a lower temperature regime obtained earlier, while the parameters for the creep-law equation are comparable with those obtained on other 7XXX aluminum alloys. We observed a change in fracture mode at 450 °C; from ductile transgranular to intergranular. This temperature coincides with the discontinuity point of the temperature-ductility slope. On the fracture surface of a sample that was deformed at 465 °C with a strain rate of 0.0005 s −1 , we observed features characteristic of micro-superplasticity. Considering the test conditions, viscous flows of incipient melt or liquid-like substances are suggested to be responsible for the formation of this feature. [ABSTRACT FROM AUTHOR]

Fatigue strength and cracking behavior of ultrathin Ag films on flexible polyimide substrates were investigated. The experimental results show that the enhanced fatigue strength of the 50 nm-thick Ag films not only is caused by the increase in the yield stress and the suppression of cyclic strain localization, but also results from the severe crack deflection induced by the formation of nanotwins, which delays the fatigue crack initiation and enhances the resistance to the fatigue crack growth. The fatigue cracking mechanism for the nanocrystalline metal films is evaluated. [ABSTRACT FROM AUTHOR]

In this work, the effect of external disturbances on the strain-rate dependent plastic deformation behavior of a Zr 57 Cu 20 Al 10 Ni 8 Ti 5 bulk metallic glass (BMG) has been examined by tailoring the geometric confinement, stress gradient, and sample size. With the external disturbances, the fracture strains of the BMG specimens become less dependence on the strain rates, and it is found that the confinement of the propagation of shear bands is the dominant deformation mechanism. This is different from previous findings in that multiplication of the shear bands also plays a critical role in accommodating the plastic deformation of BMGs with external disturbances. The present findings not only shed more light on the deformation mechanisms of BMGs under external disturbances, but also suggest that the use of external disturbances can reduce the dependence of the plastic deformation behavior of BMGs on the strain rates. [ABSTRACT FROM AUTHOR]

The dynamic tensile test with a strain rate of 500 s −1 and the quasi-static tensile test with a strain rate of 5.6×10 −4 s −1 were performed for a novel Fe-0.20C-1.49Mn-1.52Si-0.58Cr-0.05 Nb (wt%) quenching-partitioning-tempering (Q-P-T) martensitic steel with high amount of retained austenite, respectively. This low carbon steel was also treated by the traditional quenching and tempering (Q&T) process, and the same experimental tests were performed for the low carbon Q&T martensitic steel with little retained austenite to understand the effect of the retained austenite on the dynamic tensile behavior. The results indicate that compared with the quasi-static tensile test, the high strain rate in the dynamic tensile test raises the strength of the Q-P-T steel. However, the elongation slightly decreases. These results differ from the enhancement in both the strength and elongation of the Q&T steel in the dynamic tensile test. The increase in the strength of the Q-P-T steel in the dynamic tensile test is attributed to the strain rate hardening effect. The slight decrease in the elongation stems mainly from that the suppression of the dislocation absorption of the retained austenite (DARA) effect existing in the quasi-static tensile test, moreover, such a suppression is not effectively complemented by the adiabatic softening of the martensitic matrix in dynamic tensile test. The marked increase in the elongation of the Q&T steel in the dynamic tensile test is only attributed to the adiabatic softening of the martensite matrix because there is no DARA effect in the Q&T steel with little retrained austenite. [ABSTRACT FROM AUTHOR]

A polycrystalline coarse-grained Ni with 98.4 wt% purity was deformed plastically to the strain of 1.2 at the strain rate of ~10 4 s −1 using a Dynamic Hopkinson Plastic Deformation technique. The microstructure investigations indicate the ability of this loading method to process very fine microstructure with high dislocation density and large fraction of low-angle grain boundaries. It turned out that there is a transition in the mechanisms which determine the flow stress during the impact test. In the beginning of deformation viscous dislocation drag dominates, while at the end of the impact test the velocity of the individual dislocations is low due to the high dislocation density, therefore the obstacle hardening determines the flow stress. Accordingly, the flow stress measured in-situ during impact test is in good agreement with the values determined ex-situ after deformation. The main contribution to the flow stress is given by dislocations. [ABSTRACT FROM AUTHOR]

Coarse-grained (CG) metals strengthened by nanotwinned (NT) regions have an excellent combination of high strength and good ductility. In this paper, numerical simulations based on the mechanism-based strain gradient plasticity and the Johnson–Cook failure criterion are carried out to investigate the direct and indirect effects of volume fraction of the NT regions and several other key attributes on the strength and ductility of the CG metal strengthened by NT regions. Our results indicate that twin spacing, shape, distribution, and volume fraction of NT regions all have significant effects, and that, as the volume fraction increases, the roles played by the twin spacing and shape of NT regions also change. At low volume fraction of NT regions, their shape is found to have a significant influence on the overall ductility. As the volume fraction increases, the shape effect on the ductility is found to diminish even though the effect on the strength is noted to continue to enhance. While twin spacing and volume fraction of NT regions have shown different effects on the ductility, the effect of twin spacing always decreases as the volume fraction increases. During the simulations we have also discovered several intrinsic deformation and failure mechanisms through the analysis of microcrack initiation sites and microcrack propagation paths. It is believed that this simulation has revealed significant insights into the roles of volume fraction, twin spacing, shape, and distribution of NT regions on the strength and ductility of this novel class of materials. [ABSTRACT FROM AUTHOR]

In this work, experiments were conducted to quantify structure-property relations of low-cycle fatigue behavior of dissimilar friction stir welding (FSW) of AA6061-to-AA7050 high strength aluminum alloys. In addition, a microstructure-sensitive fatigue model is employed to further elucidate cause-effect relationships. Experimental strain-controlled fatigue testing revealed an increase in the cyclic strain hardening and the number-of cycles to failure as the tool rotational speed was increased. At higher applied strain amplitudes (>0.3%), the corresponding stress amplitude increased and the plastic strain amplitude decreased, as the number of cycles increased. However, at 0.2% strain amplitude, the plastic strain decreased until it was almost negligible. Inspection of the hysteresis loops demonstrated that at low strain amplitudes, there was an initial stage of strain hardening that increased until it reached a maximum strain hardening level, afterwards a nearly perfect elastic behavior was observed. Under fully-reversed fatigue loading, all samples failed at the region between the heat-affected and thermomechanically-affected zones. Inspection of the fractured surfaces under scanning electron microscopy revealed that the cracks initiated at either the crown or the root surface of the weld, and from secondary intermetallic particles located near the free surface of the weld. Lastly, a microstructure-sensitive multistage fatigue model was employed to correlate the fatigue life of the dissimilar FSW of AA6061-to-AA7050 considering microstructural features such as grain size, intermetallic particles and mechanical properties. [ABSTRACT FROM AUTHOR]

A new inverse method was developed to predict the stress–strain behaviors of constituent phases in a multi-phase steel using the load–depth curves measured in nanoindentation tests combined with microhardness measurements. A power law hardening response was assumed for each phase, and an empirical relationship between hardness and yield strength was assumed. Adjustment was made to eliminate the indentation size effect and indenter bluntness effect. With the newly developed inverse method and statistical analysis of the hardness histogram for each phase, the average stress–strain curves of individual phases in a quench and partitioning (Q&P) steel, including austenite, tempered martensite and untempered martensite, were calculated and the results were compared with the phase properties obtained by in-situ high energy X-ray diffraction (HEXRD) test. It is demonstrated that multi-scale instrumented indentation tests together with the new inverse method are capable of determining the individual phase flow properties in multi-phase alloys. [ABSTRACT FROM AUTHOR]

The fatigue properties of variable-plane-rolled (VPRed) and conventional extruded AZ31 magnesium alloy were investigated using total strain-controlled fatigue tests with various applied strain amplitudes. The results indicated that both the strength and elongation of the VPRed samples were higher than those of the conventional extruded samples because of their refined grain size and weak texture. Consequently, the fatigue lives of the VPRed samples were longer than those of the conventional extruded samples under strain-controlled cyclic loadings. The Manson–Coffin and Basquin approaches were used to describe the fatigue lifetime of this wrought AZ31 alloy. Finally, the microscopic and macroscopic fracture features were examined. The conventional extruded sample contained more extensive and well-developed twins than the VPRed sample in the stable propagation area of the cracks. The appearance of residual twins in the fracture surface resulted from the competition between the reverse plastic zone size ahead of the crack tip and the cyclic hardening–softening characteristic. [ABSTRACT FROM AUTHOR]

This paper provided a novel approach for improving the strength–ductility tradeoff in β titanium alloy through a combination of mechanical {332}<113> twins with brittle isothermal ω phase. Effects of pre-strain induced twins and subsequent precipitated ω phase on deformation microstructures, and tensile properties were investigated in a β-type Ti–15Mo alloy (mass%). Mechanical twins increased with increasing pre-strain from 1% to 9%, while formation of isothermal ω phase at 523–673 K for 3.6 ks was not significantly affected by the pre-strain induced twins. Yield strength and uniform elongation characteristics depended strongly on degree of pre-strain and aging temperature. An effective combination of 1–4% pre-strain and subsequent aging at 523–573 K markedly enhanced the uniform elongation in range of 8–15% at the yield strength level of 800–1000 MPa. The enhanced uniform elongation was mainly attributable to further twinning activation during deformation in conjunction with pre-strain induced twins. [ABSTRACT FROM AUTHOR]

The effects of stress magnitude and crystallographic orientation on the mechanical properties of stress-aged Al–2Cu alloy single crystal specimens are investigated. The specimens with ( 1 - , 1, 6) plane orientation were stress-aged under 0, 15, 40, and 60 MPa. Specimens with five different plane orientations (( 1 - , 2 - , 6), (3, 1, 3), ( 1 - , 3, 3), ( 1 - , 1, 6), and ( 1 - , 4 - , 6)) were stress-aged under stress with the same magnitude of 40 MPa. The results of mechanical properties and TEM microstructure show that the yield stress of stress-aged specimens depends on the crystallographic orientation as well as the stress magnitude. A model based on crystallographic orientation describes the precipitation strengthening of stress-aged Al–2Cu alloy. The calculated yield stresses in the model fit well with the experimental observations. This model results not only provide important insight into solving the anisotropy problem attributed to precipitation strengthening, but also offer a benchmark for choosing the right range of stress in the manufacture of Al–Cu alloys. [ABSTRACT FROM AUTHOR]

The deep-sea manned cabin endures dwell-fatigue loading process during service. The high strength titanium alloy Ti–6Al–4V ELI adopted for the manufacture manned cabin is of creep nature in the room temperature. So the dwell-fatigue property of this material should be evaluated for service life estimation. This paper presents the experimental research results on dwell-fatigue property of Ti–6Al–4V ELI. The strain accumulations under different loading conditions are reported. Results show that the strain accumulation behavior of the material under dwell-fatigue loading conditions are very similar to that under the condition of normal creep with three stages; and the increase in total strain with respect to number of cycles was much more pronounced for specimen at higher stress level, while the dwell time will affect strain accumulation when it is plotted versus cycles while strain accumulation tends to be similar in the abscissa of time for different dwell time under test. Based on the results, a dwell-fatigue life curve is derived based on the analysis, which can be applied in the material evaluation and service life estimation of the manned cabin. [ABSTRACT FROM AUTHOR]

As a type of emerging nanomaterials, lightweight metal matrix nanocomposites (MMNCs) with enhanced strength are becoming more and more attractive in recent years. However, nano-sized ceramic particles tend to form clusters during processing. In this paper, we established a physically-based plastic constitutive model to consider the detrimental effect of nanoparticle clusters on strength of MMNCs. We amended the particle size in the constitutive model with an equivalent size of both dispersed and clustered nanoparticles, which was deduced by introducing a probability density function of random distribution and a clustering extent function of nanoparticles. The model was validated by the data from literatures. The model was applied to determine important variables to improve the mechanical properties of MMNCs, including the effects of particle volume fraction, particle size, temperature, and strain rate sensitivities on the strength and flow stress of MMNCs. The model suggests that there exists a maximum strength in MMNCs versus the volume fraction of nanoparticles due to the cluster effect since it is very difficult for current processing techniques to achieve a perfectly uniform dispersion of nanoparticles in MMNCs. [ABSTRACT FROM AUTHOR]

This research investigates the effect of thermomechanical processing (TMP) parameters (temperature and strain rate) and the addition of Nb and C on the dynamic recrystallisation (DRX) of austenite and on deformation activation energy using Ni–30Fe–Nb–C and Ni–30Fe–C model alloys. Plane strain compression tests were carried out in a Gleeble TMP simulator. Critical and peak strains and stresses were determined in the temperature range of 925–1150 °C at strain rates of 0.01 s −1 , 0.1 s −1 and 1 s −1 . Both critical and peak strains and stresses increase with a decrease in the deformation temperature, an increase in strain rate or the addition of Nb in the model alloy. The Zener–Hollomon parameter and deformation activation energy values have also been determined using the experimental parameters of DRX and an Arrhenius type equation. The deformation activation energy of Ni–30Fe–Nb–C and Ni–30Fe–C were calculated to be 419 KJ/mol and 362 KJ/mol, respectively. The volume fraction of dynamically recrystallised grains determined using an Avrami type model was in good agreement with metallographic results, except for the deformation temperature near the recrystallisation stop temperature. The delayed initiation and completion of DRX due to the addition of Nb was more pronounced at lower deformation temperatures. [ABSTRACT FROM AUTHOR]

Flow forming is an old, but still promising, sheet metal forming technique to produce thin-walled, high-precision cylindrical auto-components ( i.e. carriers and clutch housings). In the present research, the flow forming process was carried out on some commonly used face centered cubic (FCC) metals to assess the effect of processing parameters on the mechanical responses of materials during flow forming. To this end, flow forming operation with thickness reduction of 70% was performed on 5052 and 6061 aluminum alloys, 70/30 brass, and pure copper. Mechanical responses of starting (as received) materials and flow formed parts, i.e. tensile strength, yield strength, elongation, work hardening rate, and work hardening exponent were discussed for each material separately and the results were compared. Also, flow formed materials were compared in terms of stacking fault energies and twinnability and the effects of these were considered on flow formability of materials and their flow behavior in flow forming operation. [ABSTRACT FROM AUTHOR]

In this work, shot peening was performed in a metastable austenitic stainless steel EN 1.4318 (AISI 301LN) in order to evaluate its effect on austenite to martensite phase transformation and also the influence on the fatigue limit. Two different steel conditions were considered: annealed, i.e., with a fully austenitic microstructure, and cold rolled, consisting of a mixture of austenite and martensite. X-ray diffraction, electron back-scattered diffraction and focus ion beam, as well as nanoindentation techniques, were used to elucidate deformation mechanisms activated during shot peening and correlate with fatigue response. Results pointed out that extensive plastic deformation and phase transformation developed in annealed specimens as a consequence of shot peening. However, the increase of roughness and the generation of microcracks led to a limited fatigue limit improvement. In contrast, shot peened cold rolled specimens exhibited enhanced fatigue limit. In the latter case, the main factor that determined the influence on the fatigue response was the distance from the injector, followed successively by the exit speed of the shots and the coverage factor. [ABSTRACT FROM AUTHOR]

Fatigue crack nucleation at a non-metallic agglomerate inclusion has been studied by high spatial resolution Digital Image Correlation (HR-DIC) and high angular resolution Electron Backscatter Diffraction (HR-EBSD). Spatial and temporal characterization and correlation of deformation with underlying microstructures has been performed, with distributions of plastic strain measured from HR-DIC; and residual stress and density of geometrically necessary dislocations (GND) measured from HR-EBSD. Initial residual stress and GND fields, as a consequence of differing thermal expansivities in the metallic and oxide phases, localized around the agglomerate have been quantified using HR-EBSD. The localization of the pre-existing stress and dislocation states appear to lead to early onset of plasticity upon subsequent mechanical loading. Heterogeneous distributions of plastic strain have been observed in the course of the fatigue test by HR-DIC. Crack nucleation via agglomerate/nickel interface decohesion and particle fracture has been demonstrated and this is correlated with the elevation in strain and dislocation density. The measurements of residual stress, strain, and dislocation density provide key information for the mechanisms of fatigue cracking and the development of damage nucleation criteria in these material systems. [ABSTRACT FROM AUTHOR]

In the present study the determining role of niobium (Nb) on significant enhancement in mechanical properties in a low-carbon quenched and partitioned steel is elucidated. The study indicates that solute drag and precipitation pinning effect of Nb suppressed the recrystallization during hot deformation, leading to grain size refinement of hot-rolled steels. The cold-rolled and final microstructure after Q–P treatment was also refined because of refined hot rolled microstructure. Additionally, the degree of refinement was enhanced with increase in Nb-content. The tensile strength of the experimental steels was increased with increase in Nb-content from 1130 MPa in steel without Nb to 1210 MPa in steel with 0.048 wt% Nb. However, the total elongation first increased to 18% followed by a small decrease to 15%. The decrease in ductility is attributed to the consumption of carbon by precipitating NbC, which decreased the enrichment of austenite by carbon during partitioning, with consequent decrease in the stability of austenite. The decrease in the stability of retained austenite ultimately reduced the volume fraction of retained austenite and led to reduction in elongation. [ABSTRACT FROM AUTHOR]

The effect of additional solute magnesium (Mg) on mechanical and high-cycle-fatigue properties of 6061-T6 aluminum alloy is investigated in detail. By adding 0.5% and 0.8% Mg to the 6061-T6 alloy with a normal stoichiometric Mg 2 Si composition (base alloy), the alloy exhibits eminent strain-aging characteristics demonstrated by the emergence of serrated flow, the negative strain-rate-sensitivity and relatively weakened temperature dependency of flow stress. The Mg-added new alloy also shows higher work-hardening rate than the base alloy particularly at initial flow regime and at lower strain rate. The S–N curve of the new alloy shows a clear fatigue limit which is absent in the base alloy. The fatigue limit of the new alloy is shown to be controlled by the threshold against small crack growth. Moreover, the new alloy clearly exhibits a coaxing phenomenon (time-dependent strengthening) which is absent in the base alloy. The coaxing effect is attributed to the existence of a small quasi-non-propagating crack whose growth resistance gradually increases during stress amplitude step-ups. [ABSTRACT FROM AUTHOR]

The effects of beryllium (Be) addition on the microstructure and mechanical properties of hot-rolled Zr–3Al– χ Be alloys ( χ =0, 0.4, 0.6, and 0.8 wt%) were characterized experimentally. X-ray diffraction and optical microscopic results indicated that the complete α phase was replaced by α phase+Be 2 Zr compound in the alloys after Be addition. Meanwhile, with an increase of Be content from 0.4 wt% to 0.8 wt%, the content of Be 2 Zr particles increased in the examined Zr–3Al– χ Be alloys. Moreover, partial α recrystallization was observed in the hot-rolled Zr–3Al alloy. The degree of α recrystallization tended to increase in the alloys with Be addition. Adding Be is beneficial to the improvement of the tensile properties. The Zr–3Al–0.8Be alloy exhibited maximum ultimate tensile strength of 1103 MPa, which increased by 27% compared with that of the hot-rolled Zr–3Al alloy and the elongation remained at 6.07%. Fractography results indicated that the fracture modes of the Zr–3Al– χ Be alloys transformed from ductile to a combination of ductile and brittle with the gradual addition of Be. [ABSTRACT FROM AUTHOR]

The effects of boron additions in an amount of 0.1–2 wt%, thermomechanical processing and heat treatment on microstructure and mechanical properties of a two-phase titanium alloy Ti–6.5Al–3.3Mo–0.3Si alloy have been investigated. Depending on the boron amount, the materials under study were divided into two groups: (1) boron modified alloys containing ~0.1 wt% of boron and (2) discontinuously reinforced metal matrix Ti–TiB based composites containing 1.5–2 wt% of boron. Boron additions led to formation of TiB whiskers, which were predominantly located along boundaries of prior β-grains and α-colonies resulting in refined as-cast microstructure. Multiple 3D forging at T =650–700 °C applied for the boron modified alloys resulted in formation of ultrafine-grained microstructure and intensive breaking of TiB whiskers. Tensile properties of the Ti–6.5Al–3.3Mo–0.3Si–0.2 wt% B alloy after multiple 3D forging followed by β-heat treatment were found to be appreciably higher than those of the alloy free of boron after the same processing route that was ascribed to better controlling the β-grain size during β heat treatment. The composite materials were subjected to multiple isothermal 2D forging at T =950 °C that provided effective alignment of TiB whiskers while retaining their high aspect ratio. The hot forged composites demonstrated appreciably higher strength, creep resistance in comparison with those of the base alloy without drastic reduction in ductility. The effect of TiB whiskers orientation and morphology on the tensile properties of the composite materials is discussed. [ABSTRACT FROM AUTHOR]

The crystallographic texture and Charpy impact toughness have been investigated in American Petroleum Institute (API) X100 pipeline steel, and the different rolling processes are applied to adjust the crystallographic texture for the sake of improving impact toughness. It has been found that the very weak textures exist in the steel only rolled in the recrystallization region of austenite, but the intensity of the unfavorable {001} 〈110〉 component is quite high. The {001} 〈110〉 texture is harmful for impact toughness and needed to be decreased in most cases. It is confirmed that the appropriate controlled rolling processes effectively reduce the intensity of the {001} 〈110〉 texture. By contrast, low temperature finish rolling in the non-recrystallization region produces the fine grain structures, beneficial textures and superior impact toughness at the low temperature. In addition, the occurrence of delamination in the ductile region generates the unfavorable cleavage crack on the fracture surface of Charpy specimen and inevitably reduces the impact energy in the upper shelf region. The delamination will occur continuously with decreasing temperature due to the large volume fraction of {001} planes parallel to the rolling plane. [ABSTRACT FROM AUTHOR]