Properties Of Alloys Research Articles

Material characterization of forged bronzes from ancient China (c. 11th-2nd century BCE) reveals development of the non-mainstream metalworking technique in Chinese bronze production

Although ceramic piece-mould casting was the dominant metalworking technique in the Chinese Bronze Age (c. 2100-221 BCE), the forging technique was also employed by craftsmen to pursue lightweight bronzes with thin walls and high hardness. However, compared to the ceramic piece-mould casting technique, research on forging technology is relatively limited. In this research, 48 sheet metal fragments of Chinese bronzes from different regions and periods (from the Zhou to Han dynasties) across China were analyzed by metallography, SEM-EDS, and hardness testing. The results show that craftsmen had a profound understanding of copper alloy properties and were able to produce thin-walled, functional artifacts by forging cast blanks with appropriate alloy compositions. With the development of forging technology and political changes, the types of forged thin-walled bronzes became more diverse, and their consumers expanded from the elite to civilians. This study not only reveals the material characterization of forged bronzes, but also elucidates the historical trajectories of forging technology and the multifaceted interplay between cultural influence, aesthetic pursuits and technological advancement in the development of forging techniques in ancient China.

Influence of Hot Rolling on Microstructure, Corrosion and Mechanical Properties of Mg–Zn–Mn–Ca Alloy

The effect of hot rolling on the microstructure, mechanical, and corrosion properties of the magnesium alloy 96 wt% Mg–2.3 wt% Zn–0.7 wt% Ca–1 wt% Mn was studied. After heat treatment, the original plates of an as-cast alloy were rolled from a 7 mm thickness to a 0.2 mm thickness at two temperatures—300 or 400 °C. It has been established that increasing the rolling temperature from 300 to 400 °C increases the fraction of recrystallized grains in the microstructure and after rolling at 400 °C, the microstructure is fully recrystallized. The best strength–ductility balance of the alloy was obtained after rolling at 300 °C, with a high total percentage reduction of 93–97%: the yield stress, the ultimate tensile strength, and the elongation averaged at 285 MPa, 310 MPa, and 5%, respectively. The alloy after rolling, annealed at 400 °C, shows improved ductility but lower strength: the yield stress, the ultimate tensile strength, and the elongation were 200 MPa, 260 MPa, and 17%, respectively. The strong dependence of corrosion resistance on respect to rolling direction is observed, which can be reduced after heat treatment. The as-rolled alloy and the heat-treated alloy had low corrosion rates in Hanks’ solution of 0.54 and 0.19 mm/year, respectively.

Role of structural ordering on magnetostrictive property of Fe-Ga alloys

Role of structural ordering on magnetostrictive property of Fe-Ga alloys

The tensile behaviors of Ag-Cu alloys with different Cu contents: Molecular dynamics simulations study

The Ag-Cu alloys have received attention due to their excellent electrical and mechanical properties. However, the analytical research on why the mechanical properties of the Ag-Cu alloys increase after a small amount of Cu atoms are added is still lacked. In this work, the classical molecular dynamics (MD) simulations method was used to establish the Ag-Cu alloy models with different Cu contents. The tensile deformation mechanism of Ag-Cu alloy at room temperature was revealed from the atomic scale through the analysis of the stress-strain behavior and the evolution of dislocations. During the simulations, the embedded atom method (EAM) potential was used to describe the interaction between Ag atom and Cu atom. The uniaxial tensile deformation and nanostructure evolution of Ag-3 at.% Cu, Ag-6 at.% Cu and Ag-10 at.% Cu alloy models at the temperature of 300 K and the strain rate of 0.02 Å/ps were studied in detail. Results show that the internal stress was generated due to the large lattice mismatch among Ag atom, Cu cluster and the grain boundary. It results in the formation of dislocation and the negative initial stress at the beginning stage of Ag-Cu alloy models under tension. The dislocation firstly nucleates at the grain boundary and the growth rate of dislocation is slow before the crack propagation, and the complex dislocation reactions also exist. With the increase of Cu content, the tensile strengths of Ag-Cu alloys also increase. Cracks mainly form at the intersection of multiple grains, and the fracture mode changes from the intergranular fracture to the intergranular fracture and transgranular fracture after the unstable propagation of cracks. Meanwhile, a plenty of Cu atoms are distributed in the form of clusters in Ag matrix. They hinder the slip of dislocation and slow the relative sliding between atomic layers, and thus finally improves the deformation resistance to the plastic deformation of Ag-Cu alloy. The study on the tensile deformation behavior of Ag-Cu alloy at room temperature has certain guiding significance for the practical production and application of the design of Ag-Cu alloy.

Study on Microstructure and Properties of AlCoCrFeNi High-Entropy Alloys by Extreme High-Speed Laser Cladding

AlCoCrFeNi HEA powders were cladded onto AISI 1045 steel using EHLA and CLA, respectively. The phase composition, microstructure, micro/nanohardness, and corrosion resistance of the two coatings were compared and analyzed. The results show that the phase structure of AlCoCrFeNi HEA coatings prepared by EHLA and CLA was that of a BCC/B2 phase solid solution. From the bottom to the top, the EHLA-derived AlCoCrFeNi HEA coating experienced evolution in the microstructure of plane crystal, dendrite, and equiaxed crystal. The micro/nanohardness of EHLA-derived coating (~507 HV0.2, 6.716 GPa) is higher than that of CLA-derived coating (~429 HV0.2, 5.778 GPa). The electrochemical test results show that the Ecorr of CLA is −0.527 V and the Icorr of CLA is 1.272 × 10−7 A/cm2, while the Ecorr of EHLA is −0.454 V and the Icorr of EHLA is 1.588 × 10−8 A/cm2, which means that the corrosion resistance of EHLA is better.

Effect of manufacturing route on microstructure and micromechanical properties of AlCoCrFeNi high entropy alloy

The manufacturing route of a particular metallic alloy profoundly affects its microstructure, as well as mechanical properties. In that respect, the present research investigates the microstructure and microstructure-dependent mechanical properties of the AlCoCrFeNi high entropy alloy (HEA), that was manufactured via two different routes: (i) Atmospheric plasma spraying (APS) in the form of coating on a stainless steel subtract and (ii) vacuum arc melting (VAM) in the form of bulk material. AlCoCrFeNi HEA coating microstructure is composed of a solid solution (Ni) as a matrix, which contains different phases, as well as intermetallics and defects, such as splat boundaries. On the contrary, the microstructure of bulk AlCoCrFeNi HEA alloy is free from any secondary phases, and is homogeneous in nature, which consists of only the solid solution of Ni. The experimental results show that the strength of the bulk HEA (963.14 ± 28.58MPa of yield strength and 1005.58 ± 22.08MPa of compressive strength) is better than that of HEA coating (yield strength of 802.33 ± 43.76MPa and compressive strength of 817.73 ± 43.84MPa). The phase, as well as splat boundaries in the microstructure, are the ‘weakest link’ in the HEA coating, that serves as defect initiation site. As the bulk HEA alloy is free from these ‘weakest link’, thus, deformation of the material is guided through plastic flow of materials, in the terms of the barrelling effect.

Effect of heat treatment on microstructure and mechanical properties of WE43 alloy fabricated by wire arc additive manufacturing

Heat treatment is an effective method to improve the mechanical properties of Wire Arc Additive Manufacturing (WAAM) WE43 alloy. This study investigates the effects of heat treatment on the microstructure and mechanical properties of the WE43 alloy processed by WAAM. The as-deposited samples exhibit a uniform equiaxed crystal structure, with grain size gradually increasing as the number of deposited layers grows. The as-deposited microstructure comprises eutectics and a small amount of cubic phases, and the phase content escalates as the amount of deposited layers increases, influenced by the cumulative effect of multiple thermal cycles. At lower solid solution temperatures (480 ℃ × 8h), most of the eutectic phase remains undissolved. During tensile testing, undissolved eutectics tend to cause stress concentrations, leading to cracks that result in sample fractures, negatively affecting the mechanical properties. At higher solid solution temperatures (520 ℃ × 8h), most of the eutectic dissolves, but abnormal grain coarsening (AGC) in the interlayer fine-grain region occurs, causing a significant reduction in the sample's mechanical properties. After solid solution treatment at 500 °C for 8hours, only a small amount of eutectics remains undissolved, and the AGC phenomenon is not observed, resulting in an optimal solid solution effect. Subsequently, after aging treatment at 225 °C for 18hours, dense nanoscale β′′ phases precipitated within the alloy grains, significantly improving the mechanical properties. The samples achieved optimal performance, with UTS, YS, and EL of 323±15.2MPa, 225±11.3MPa, and 8.4±1.1%, respectively.

Effect of wall thickness on the precipitation behavior, microstructure, electrical conductivity and mechanical properties of copper alloy prepared by electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF) is one of the most promising technologies for preparing thin-walled copper alloy, because copper alloy have a high energy absorption rate for electron beam, and high preheating temperature can reduce the solidification temperature gradient and reduce the deformation of thin-walled parts. At present, there are few reports on the systematic research work on the EB-PBF of thin-walled CuCrZr alloy parts, and it's impossible to effectively supervise the production of complex thin-walled CuCrZr alloy parts. This work aims to investigate the effect of thickness on the microstructure and mechanical properties of CuCrZr alloy produced by EB-PBF. As the wall thickness decreases from 5.0 mm to 0.3 mm, the grain sizes of the XY and YZ planes decreased from 20.4 μm and 43.1 μm to 14.5 μm and 21.5 μm respectively, and the texture intensity decreased from 16.04 and 23.57 to 7.62 and 10.99. The analysis showed that Cr2O3 nanoprecipitates were precipitated in situ in the sample, and their average size decreased from 65.8 nm to 21.6 nm. Due to the reduction in grain and nanoprecipitate size, the performance of thin-walled samples is significantly enhanced, with yield strength (YS) increasing from 112 MPa to 165 MPa and conductivity increasing from 71.7 %IACS to 86.1 %IACS. Finally, the main contributions to the YS of specimens with different wall thicknesses was discussed. Precipitation strengthening and dislocation strengthening are the main strengthening mechanisms in thin-walled samples, and the gradual refinement of nano-precipitates is the main reason for the improvement of mechanical properties as the wall thickness decreases.

In-situ synthesis of Yttria-based precipitates and their effects on Fe12Cr6Al in laser powder bed fusion

To advance the suitability of FeCrAl alloys for nuclear applications, radiation damage resistance, creep resistance, corrosion resistance, and mechanical properties enhancement are essential. A promising approach is the introduction of a high density of nitride and oxide nanoprecipitates within the alloy matrix. This study aimed to explore the impact of in-situ formed nitride and oxide precipitates on the properties of Fe12Cr6Al alloy by using a nitrogen-rich atmosphere and incorporating nano-sized Y2O3 (0.45 wt. %) during laser powder bed fusion (LPBF). As a result of adding Y2O3 nanoparticles to the Fe12Cr6Al alloy, the grain size decreased from 70 μm to 40 μm, and the Al-O, Al-N, and Al-N-O precipitates were replaced by Y-O, Y-Al-O, and Y-N precipitates. Additionally, the nitrogen contents increased from 220 ppm to 470 ppm. The sample with Y2O3 exhibited higher mechanical properties, with yield strength, tensile strength, and hardness (HV) increasing by 80 MPa, 112 MPa, and 23 HV, respectively. This study deviates from previous research on Y2O3-containing FeCrAl alloys by investigating the impact of in-situ synthesized Y-N nitrides on Fe12Cr6Al. The objective is to elucidate the combined effects of these precipitates on the properties of Fe12Cr6Al alloy in comparison to literature-reported oxide dispersion-strengthened (ODS) FeCrAl alloys, which were fabricated in an argon (Ar) atmosphere.

Effect of grain boundary engineering on corrosion behavior and mechanical properties of GH3535 alloy in LiCl-KCl molten salt

This study investigated the effect of grain boundary engineering (GBE) on the corrosion behavior and high-temperature mechanical properties of GH3535 alloy in 45LiCl-55KCl wt.% molten salt at 550°C. After corrosion for 300 h, a triple-layered product was formed on the solid solution specimen (Non-GBE), consisting of discontinuous NiCr2O4 outer-layer, Ni3Fe middle-layer, and NiCr2O4 inner-layer. For the GBE specimen, quite milder corrosion occurred on it that its surface still kept original polishing scratches. The real mass loss of the Non-GBE alloy (6.85 mg/cm2) is one order of magnitude higher than that of GBE (0.65 mg/cm2). The beneficial effect of GBE on improving alloy's corrosion resistance is owing to: surface carbide dissolution, discontinuous random high angle grain boundary and low dislocation density. High proportion of Σ3n grain boundaries and less carbide precipitation ensure stable high-temperature deformation performance of GBE sample in molten salt.

Influence of aging heat treatment on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 high-entropy alloys strengthened by nano-precipitates

Nanoprecipitation strengthening represents a highly effective strategy for enhancing the mechanical properties of high-entropy alloys (HEAs). While existing research primarily concentrates on elucidating the strengthening mechanisms, comparatively limited attention has been paid to the processing technologies, which are equally vital for the industrial application of these materials. In this study, we systematically investigate the effects of aging heat treatment at various temperatures (300-800 °C) and durations (0.5-12 h) on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 HEA, which is reinforced by nanoprecipitates. Our findings indicate that aging the alloy at 700 °C for 4 h increases the yield strength from 323 MPa to 440 MPa compared to the as-cast alloy, representing a substantial enhancement in strength of 36%. However, this improvement is accompanied by a slight reduction in plasticity. This enhancement is attributed to successfully forming uniformly distributed coherent nanoprecipitates within the alloy matrix. Furthermore, an evaluation of the strengthening contribution based on dislocation pinning theory suggests that nanoprecipitation is the predominant mechanism responsible for this increase in strength. These results underscore the critical role of processing parameters in optimizing the mechanical performance of HEAs, thereby facilitating their broader industrial applications.

Large and reversible elastocaloric effect induced by low stress in a Ga-doped Ni-Mn-Ti alloy

The Solid-state cooling based on caloric effects is considered a potential alternative to conventional refrigeration technology, which uses ozone-depleting gases. Several shape memory alloys have attracted attention for solid-state cooling since they present a high reversibility of the caloric effect, which depends mainly on thermal hysteresis and sensitivity to the applied field. In the present work, a study substitution of Mn by Ga in the Ni50Mn34Ti16 alloy led to diminished thermal hysteresis in the martensitic transformation by 6 K. The elastocaloric effect, thermal and microstructure properties of a polycrystalline Ni50Mn32Ti16Ga2 alloy have been characterized. The elastocaloric effect was obtained indirectly from the length change as a function of temperature at constant stress. An isothermal entropy change (ΔSISO) of 23.0 J kg−1 K−1 during heating and 22.0 J kg−1 K−1 during cooling was observed for applied stress of 160 MPa. In addition, the ΔSISO is reversible for a temperature span between 287 and 319 K, reaching a maximum of 20.5 J kg−1 K−1 at 299 K. The thermal hysteresis changed slightly while the applied stress increased up to 160 MPa since the sensitivity of the martensitic transformation temperatures to stress was 0.150 K M/MPa during cooling and 0.160 K/MPa during heating. The X-ray diffraction analysis revealed a mixture of B2-type cubic austenite, 5 M modulated martensite, and a second intermetallic phase identified as Ni3Ti. All these results were obtained around room temperature.

Effect of laser remelting on the microstructure and properties of an AlCoFeNi eutectic high-entropy alloy fabricated through double-wire arc additive manufacturing

Additive manufacturing (AM) technology is a new method for preparing eutectic high-entropy alloys (EHEAs). The resulting EHEAs have excellent mechanical properties. However, in engineering, material failure, such as wear or fatigue fracture, often occurs on the surfaces of components. There is no report on surface modification and strengthening of additively manufactured EHEAs. Therefore, this study successfully utilized laser remelting (LR) technology to enhance the surface properties of an AlCoFeNi EHEA fabricated by using double-wire arc AM technology. After LR, the distance between adjacent regular eutectic regions and lamellar spacing of the EHEAs significantly decreased, and the proportion of strictly semicoherent face-centered cubic/body-centered cubic interfaces increased. When microhardness increased from 277.7 HV to 302.3 HV, the average friction coefficient and wear rate of the alloys decreased by 32.5% and 51.1%, respectively, and hardness and wear resistance significantly improved. This study has laid a solid foundation for the engineering application of the combination of LR and AM and also provided new ideas for improving the surface performance of additively manufactured EHEAs.

Effects of ultrasonic nanocrystal surface modification treatment and subsequent annealing on the microstructure and mechanical properties of rolled AZ31 alloy

Effects of ultrasonic nanocrystal surface modification treatment and subsequent annealing on the microstructure and mechanical properties of rolled AZ31 alloy

Significantly enhanced mechanical properties of NiCoV medium-entropy alloy via precipitation engineering

Significantly enhanced mechanical properties of NiCoV medium-entropy alloy via precipitation engineering

Direct and indirect assessment of the elastocaloric properties of cast NiMnTi alloys

Direct and indirect assessment of the elastocaloric properties of cast NiMnTi alloys

The effect of graphene nanoplatelets on the aging precipitation behavior and mechanical properties of magnesium matrix composite

Aging can effectively improve the mechanical properties of Mg alloys. The reinforcements can affect the aging kinetics of composites through interaction with the matrix. In this study, the effect of graphene nanoplatelets (GNPs) on the precipitation behavior of Mg-6Zn/GNPs composite was studied. The local region with high GNPs content exhibits a faster aging precipitation rate. Compared with Mg-6Zn alloy, the aging precipitation process of the composites has been accelerated as a whole. It is mainly attributed to the fact that the high density of dislocation near GNPs provides a high-speed channel between nucleation points and atoms for aging precipitation, which promotes aging precipitation. The strengthening effect of the composites mainly results from Orowan strengthening and fine grain strengthening generated by Mg4Zn7 and GNPs, respectively. The existence of GNPs enhances the aging hardening efficiency of the composites to a greater extent than that of the alloy matrix. This work provides a new approach for the design of aging behavior in magnesium matrix composites.

Expansion of thermodynamic calculation principle of multi-component alloy and its application in the study of thermodynamic properties of the Cr-Mo-Nb-V high entropy alloy

In this paper, based on the improved Miedema model and the quaternary alloy calculation model expanded by Chou model, the activity calculation model of the ternary alloy system is extended to the quaternary alloy system through the ternary alloy activity calculation model of Wagner and Ma Zhongting et al.. In addition, a new deviation function is used in the expanded quaternary alloy calculation model to calculate the thermodynamic properties of quaternary alloys, which meets the characteristics of both non-negativity and reducibility. Using the developed model, this paper calculates the thermodynamic data of each sub-binary, sub-ternary, and quaternary system in the Cr-Mo-Nb-V quaternary high entropy alloy system. Subsequently, this paper analyzes the interactions between components, predicts the possible precipitated phases in the alloy system, and explains the possibility of forming a solid solution in the alloy system. The final results are consistent with those shown in the literatures on studying the Cr-Mo-Nb-V quaternary alloy system, which verifies the applicability of the developed model in the miscible alloy system, enriches the thermodynamic database of Cr-Mo-Nb-V alloy, and provides theoretical reference and ideas for the design of multi-component alloys.

Microstructure and mechanical properties of WE43 magnesium alloy fabricated by wire-arc additive manufacturing

Microstructure and mechanical properties of WE43 magnesium alloy fabricated by wire-arc additive manufacturing

Variation of Corrosion Characteristics and Tensile Performances of WE43 Alloy Under Marine Atmospheric Environment.

This study aims to examine the variation in corrosion characteristics and tensile properties of WE43 magnesium alloy in an actual marine atmospheric environment by means of outdoor exposure tests. The macroscopic corrosion morphology, microstructure, and tensile properties were analyzed. The results indicated that WE43 alloy will corrode rapidly during exposure under marine atmospheric environmental conditions, resulting in a loose and porous Mg(OH)2 layer on the surface. The Mg matrix was mainly consumed as an anode, leading to the occurrence of corrosion pits. With the increase in exposure time, both the tensile strength and plasticity of WE43 alloy gradually deteriorated. After exposure for six months, the elongation and area reduction were significantly reduced, with a reduction ratio of more than 50%. After 18 months of exposure, the ultimate strength of the alloy decreased from 359 MPa to 300 MPa. According to an analysis of fractures in the alloy, the corrosion pits on the sample surface were the main reason for the decrease in tensile properties.