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• As Nb content increases, the damping capacity is broadly improved. • The enhanced damping capacity is attributed to the Snoek relaxation. • Larger α 2 /γ lamellar colony have an adverse effect on damping capacity. The effect of Nb content on the damping capacity of the as-cast Ti-47Al-xNb-2Cr-0.2Mo alloys (at. %) (x = 1, 3, 5, 7) was investigated. The results showed that increasing the Nb content can broadly improve the damping capacity in TiAl-xNb alloys, which profits from the Snoek relaxation. TiAl-3Nb exhibits poorer damping capacity than TiAl-1Nb due to its larger α 2 /γ lamellar colonies. [ABSTRACT FROM AUTHOR]

• A high-damping C-containing Fe-Mn-Cr-Ni medium entropy alloy (MEA) was designed. • The internal friction peak value at 550 K of the Fe-Mn-Cr-Ni MEA is about 0.083. • The Finkelstein-Rosin (FR) relaxation mechanism is meticulously discussed. • This high damping performance can be attributed to the FR relaxation. Construction machinery noise not only affects its service life, but also brings hazards to people's physical and mental health. Achieving a high and stable internal friction characteristic to eliminate noise and mechanical vibrations is always the desired goal in the design of damping alloys. In the study, we present a C-containing Fe-Mn-Cr-Ni medium entropy alloy that exhibits a superior damping capacity with an internal friction peak value of 0.083. The Finkelstein-Rosin relaxation peak appears at 550 K in the internal friction spectrum, which is attributed to the reorientation of C-C pairs and C substitutional atom pairs under stress, with the diffusion activation energy are 155.172 kJ·mol−1 and 166.711 kJ·mol−1, respectively. The relaxation of Finkelstein-Rosin peak enhances the damping capacity of the alloy, which provides an effective method for regulating the damping properties of medium entropy alloys. [ABSTRACT FROM AUTHOR]

• ZA22/Al interpenetrating composite (IPC) was prepared for the first time. • Specimens were prepared using a two-step air pressure infiltration method. • ZA22/Al IPC has a high compressive stress plateau and a high damping capacity. • The microstructure origin of excellent comprehensive properties of IPC was discussed. A ZA22/Al interpenetrating phase composite (IPC) was prepared by a two-step infiltration method for the first time. The ZA22 alloy and the Al matrix were well bonded together, and a layer with ultrafine grains containing Al, Zn and O elements was formed between them. Lamellar eutectoid structure (LES) in original ZA22 alloy transformed to granular eutectoid structure (GES) with submicron sized α and η phases, resulting in a significant increase in phase interface density. The property test results showed that the IPC has a high compressive stress plateau and a high damping capacity up to 0.2. Correlated mechanisms were discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polymer derived aluminum foam had triple the damping capacity of solid alloy. • Damping in aluminum foam positively correlates with temperature and frequency. • Microscopic pores in aluminum cause high damping due to mode conversion. Aluminum foams have excellent high-temperature damping capabilities. However, the use of metallic hydrides to synthesize foams reduces cell ductility, due to brittle intermetallics. This study demonstrates the damping behavior of AA2024 alloy foam synthesized using Polymethyl Hydrogen Siloxane as a foaming agent. Damping capacity was studied as a function of temperature (25 to 300 °C), frequency (1 to 80 Hz) and stress amplitude (1.5 to 21.5 MPa) using Dynamic Mechanical Analyzer. For comparison, monolithic samples of AA2024 at various conditions were also tested. The damping capacity of foams was about three times higher than the monolithic samples under certain conditions. The increased damping was a consequence of dislocation activity resulting from mode conversion around the numerous microscopic pores in the aluminum foam. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiTip/7075Al composites have phase-transformation damping characteristics. • Phase-transformation and damping temperature of the composites can be controlled by heat treatment. • The composites shows excellent low-temperature damping performance while maintaining well tensile strength. • The damping mechanism of NiTip/7075Al composites was analyzed. To achieve controllable damping temperature zones in aluminum matrix composites, the NiTip/7075Al composites with controllable phase transformation characteristics were prepared through friction stir processing (FSP) and heat treatment. Aging of NiTi particles led to a downward shift in the phase-transition peak temperature of the composite, accompanied by a sharper peak. During the cooling process, the as-NiTip/7075Al + T6 composites underwent a B2 → R transformation and an R → B19′ transformation. Furthermore, the T6 treatment effectively enhanced the tensile strength of the composites. The damping properties of NiTip/7075Al composites at low-temperatures (<90 °C) were significantly superior to those of FSP-7075Al alloy. The as-NiTip/7075Al + T6 composites exhibited two internal friction peaks during cooling, which were 153 % and 211 % higher, respectively, than those observed in the FSP-7075Al alloy at corresponding temperatures. The damping temperature range of the composites can be effectively controlled through T6 treatment and NiTi particle pre-aging. [ABSTRACT FROM AUTHOR]

• Cryogenic laser peening (CLP) can enhance the mechanical properties of pure Ti. • CLP can improve the damping capacity of pure Ti. • The simultaneous improvements were contributed to the twins induced by CLP. In this study, the effects of cryogenic laser peening (CLP) on mechanical properties and damping capacity of pure titanium (Ti) were explored. The experimental results showed that CLP improved the tensile properties and in-depth microhardness of pure Ti, while the compressive residual stress was introduced in the surface layer. Meanwhile, the damping ratio was also increased after CLP process. The synergistic strengthening effect of CLP could effectively accelerate the formation of deformation twin, which contributed to the simultaneous improvement in mechanical properties and damping capacity of pure Ti. [ABSTRACT FROM AUTHOR]

Highlights • ECAE processing improves the strength of grade 4 titanium at room temperature due to its UFG structure. • ECAE processing improves the ductility of grade 4 Ti at 600 °C. • Damping capacity of ultrafine-grained Ti is improved over its coarse-grained counterpart. • Damping behavior was shown to be time dependent at ambient conditions, albeit no dependency at 600 °C. Abstract In this work, influence of severe plastic deformation on the damping properties of commercial purity titanium is explored. Deformation induced grain refinement improved the strength at room temperature while this effect diminished at a high temperature of 600 °C. Ultrafine-grained titanium demonstrated higher damping capacity as rationalized with the enhanced contribution of increased defect density. [ABSTRACT FROM AUTHOR]

• A novel technique was developed to fabricate Al matrix composites. • In the Al matrix composites, SiC p and carbon fibers were evenly distributed. • The mechanical and damping properties of the Al matrix composites were improved. A colloidal dispersion and suction filtration novel technique was developed to fabricate SiC particles (SiC p) and carbon fibers (C fs) synergistically reinforced Al matrix composites (SiC p -C fs /Al composites). The SiC p and C fs could be uniformly inserted into the Al matrix by the approach, and the manufactured SiC p -C fs /Al composites exhibited a dense structure, according to microstructural observations of the composites. The tensile strength and damping capacity of SiC p -C fs /Al composites were dramatically increased when compared to SiC p reinforced Al matrix composites. The homogenous distribution of SiC p and C fs in the Al matrix, which offers an excellent synergistic strengthening effect, is responsible for the simultaneous improvement of the strength and damping properties of the SiC p -C fs /Al composites. [ABSTRACT FROM AUTHOR]

• The present paper mainly investigates the damping behaviour of AA6061. • Grain refinement was studied with the help of electron back scattered diffraction. • Intermetallic behaviour was studied under the scanning electron microscope. • Damping behaviour is correlated with grain size and intermetallic behaviour. The effect of brass interlayer and water cooling on the damping behavior of friction stir welded AA6061 was investigated in the present work. The results revealed that weld samples showed better damping capacity than base metal attributed to the grain refinement. Moreover, the damping capacity of weld with the addition of interlayer is enhanced due to more grain refinement, formation of hard intermetallics, and high inherent damping capacity of brass. The reduced intermetallics and formation of smooth interface obtained for water-cooled weld attributed to the faster cooling rate improved the mobility of grain boundaries which enhanced the damping capacity than natural cooling. The water-cooled weld with interlayer showed better damping at high temperatures than other weld joints due to the increased grain boundary area. [ABSTRACT FROM AUTHOR]

• An innovative graphene oxide/TiNi laminate composite sheet was designed and prepared. • The continuous Ti 2 Ni and TiC reaction layers were generated along the GO/TiNi interface without obvious disjunct. • The composite sheet showed superior damping properties than TiNi alloy and TiNi laminate sheet without GO. In this paper, the interfacial microstructure and damping behavior of the novel graphene oxide/TiNi laminate composite sheet (GO/TiNi) were characterized. Results showed that the well-bonded GO/TiNi interface and alternating laminate structure were obtained in the composite sheet. The continuous reaction layer adjacent to the TiNi matrix was detected as the Ti 2 Ni phase with cubic structure, and the reaction layer near the GO was confirmed as the TiC nanocrystalline. The rhombohedral Ni 4 Ti 3 phase could be tracked to precipitate within the TiNi matrix. Compared with the TiNi alloy and TiNi laminate sheet without GO, the GO/TiNi laminate composite sheet has the optimal intrinsic damping capacities with the tanδ (martensite) of 0.089 and tanδ (austenite) of 0.034, which are attribute to the effective introduction of the high damping GO reinforcement. [ABSTRACT FROM AUTHOR]

A NiTi/Mg composite was fabricated using a method that combines top-down pore-forming and pressureless infiltration processes. The phase constituents of this simple composite are B2-NiTi, B19′-NiTi and Mg phases. Both the size and the distribution of the Mg-phase are fine and homogeneous. The composite has very high mechanical strength and damping capacity, ~1.2 and 1.5-fold higher than those of a similar composite with different microstructures, respectively. These behaviors are generally attributed to the high damping capacity of Mg, the physical continuity of the composite, and the homogeneous distribution of fine Mg-phase, which generate more interfaces, contributing to the damping capacity. This composite is considered a good candidate for use as a damping material in engineering applications. [ABSTRACT FROM AUTHOR]

• Parallel distribution of second phases in as-cast Mg-Gd alloys are obtained. • Mg-Gd alloys still retain high damping capacities with increasing element content. • Mg-Gd alloys still retain high damping capacities with improved strength. • Mg-Gd exhibits promising potential for developing high-performance damping alloys. In this study, we aim at the inherent contradiction that the addition of elements with strong solid solubility strengthening effect in Mg leads to a sharp deterioration of damping capacities. It is proposed that utilizing the element with the low growth restrict factor (GRF) can form parallel distribution of second phases in solidification microstructure to impede the sharp deterioration of damping capacities with increasing element content. In cast Mg- x Gd (x = 1, 1.5, 3, 6 wt%) binary alloys, with increasing Gd (GRF = 1.03) content from 1 wt% to 6 wt%, the damping value Q −1 decreases from 0.16 to 0.05 due to the existence of the parallel distribution of second phases at the strain amplitude of 0.8 × 10−3, while the yield strength increases 30 MPa to 84 MPa. Compared with the reported sharp decrease in damping properties of high-damping Mg-Y alloys with increasing Y content, Mg-Gd alloys could be promising potential candidates for developing high-performance damping magnesium alloys (Q −1 ≥ 0.01). [ABSTRACT FROM AUTHOR]

[Display omitted] • Synchronous change in magnetostriction and damping in Fe-16Cr-0.6Mo-0.6Al alloy. • Damping as a function of amplitude and frequency of forced vibrations. • Damping is interpreted in terms of variations in relaxation time and stiffness of DMA. The magnetostriction, damping capacity and mechanical properties of a Fe-Cr-Mo-Al alloy are studied and compared with binary Fe-Cr and Fe-Al alloys. Synchronous change in magnetostriction and damping in Fe-16Cr-0.6Mo-0.6Al alloy: the maximum magnetostriction strain and damping capacity are obtained after annealing at 900 °C followed by air cooling. Frequency dependence of damping in subresonance range is analyzed and interpreted in terms of variations in relaxation time and stiffness of DMA. [ABSTRACT FROM AUTHOR]

Abstract: A new idea of using a stiffer metallic compound Mg2Si to enhance the damping capacities of Mg2Si/Mg–9Al is successfully attempted. Results show that Mg2Si/Mg–9Al composite materials have better damping capacity than non-reinforced alloy. Damping capacities of composite materials have been improved further after morphology modification of Mg2Si particles. Particular emphasis is placed on the increasing dislocation density around matrix–particulate interface and effect of modification of antimony on damping capacity. [Copyright &y& Elsevier]

Abstract: A new idea of using a stiffer metallic compound Mg2Si to enhance the damping capacities of pure magnesium and its alloys is successfully attempted. The present paper focuses on the relation between damping capacities and the addition amount of Si. The results show that damping capacities increase with increasing amount of Si. Particular emphasis is placed on the increasing dislocation density around matrix–particulate interface and the refinement of grain size promoted by big growth restriction factor of Si. [Copyright &y& Elsevier]

Abstract: The damping properties of the hollow sphere fly ash/6061Al composites with various reinforcement diameters and with about 40 vol.% porosities (enclosed within the hollow sphere fly ash particles) have been measured by using the forced vibration mode and the bending–vibration mode on the multifunctional internal friction apparatus. The results indicate that the damping capacity of the fly ash/6061Al composite with smaller reinforcement diameter is higher than that with larger reinforcement diameter in both vibration modes. In the bending–vibration mode, there is a more significant increase in the damping capacity of the as-received commercial 6061Al due to the addition of fly ash particles and the damping capacities of the fly ash/6061Al composites can reach (2–3)×10−2, which is more than two times of the maximum values measured in the forced vibration mode. But this phenomenon has not been found in the as-received 6061Al. The related mechanism has also been discussed. [Copyright &y& Elsevier]

Abstract: Damping capacity of in situ TiB2 particulate reinforced aluminum composites with Ti and Mg excess were investigated. The composites were fabricated with an exothermic reaction process via K2TiF4 and KBF4 salts. The damping behavior of materials over a temperature range of 30–300 °C was investigated by using a dynamic mechanical thermal analyzer. Experimental findings indicate that the damping capacity of composites with Ti, Mg excess, respectively is lower than that of Al/5 wt.% composite when temperature is below 180 °C and is higher than of Al/5 wt.% composite above 180 °C. The main effects of these elements are the formation of thin layers on TiB2 particulates, which resulted in the change of damping capacity. [Copyright &y& Elsevier]

Abstract: JR-6 nano-grain refiner was employed to investigate mechanical properties and damping capacity of A356 alloy after grain refinement. Experimental findings indicate that α-Al dendritic arm spacing reduced from 44 μm to 23 μm in size after grain refinement. With T6 heat treatment, gliding fracture only was observed by SEM on fracture region after refinement, which filled with dimple fully. Tensile testing results show that A356 alloy after refinement has better mechanical properties, which increased by 30 MPa, 24 MPa, 4.1% in tensile strength, yield strength and elongation, respectively. Damping measurement shows damping capacity of A356 alloy after grain refinement is higher than that of without refinement. Moreover, damping capacity increases with increasing the temperature and decreases with increasing frequency. With testing condition of room temperature and frequency of 0.5 Hz damping capacity of A356 alloy after grain refinement is 13×10− 3, increased by 5×10− 3 compared to A356 without refinement in same case. Also damping mechanisms are discussed basing on experimental results. [Copyright &y& Elsevier]

Abstract: A novel model for calculating the damping capacity of continuous fiber-reinforced metal matrix composites (FMMCs) is proposed based on the viewpoint of energy loss. Finite element method (FEM) has been employed to investigate the effect of fiber coating on the longitudinal damping capacity of a composite by varying the thickness and the material properties of the coating. The results show that the damping of a composite containing the elastic coating increases with a decrease in the elastic modulus of the coating, while for the case of plastic coating, the weak coating or the high elastic modulus coating may help in improving the overall damping of composite. [Copyright &y& Elsevier]

A new model for calculating the damping capacity of particulate-reinforced metal matrix composites (PMMCs) is proposed based on the assumption that the energy loss mainly results from the anelasticity of the particulate and matrix and the micro-plasticity of the matrix under small strain amplitude. Finite element method (FEM) with a multi particle model has been adopted. The results show that the energy loss in the loading direction can represent the total energies consumed in the composites. Moreover, the results calculated with the new model show good coincidence to the Granato–Lu¨cke theory, which demonstrates the feasibility of damping calculation with the method. [Copyright &y& Elsevier]

• Porous structure and large numbers of interparticle interfaces are formed in the particle layer. • Damping capacity and storage modulus are simultaneously improved by the particle layer. • The comprehensive damping index of the composites is superior to the 5052 Al alloy. • The damping mechanism of AlSi30 p /5052Al composites was analysed. The AlSi30 p /5052Al composite with porous particle layer was successfully produced by hot rolling. Numerous interparticle interfaces and pores were seen in the particle layer. The dynamic mechanical analysis shows that the internal friction and the storage modulus of the composites are higher than that of the matrix. Due to the presence of an intermediate particle layer, dislocation and residual internal stress increase in the composites, and thereby improve the storage modulus of the composites. The comprehensive damping index of the composites is better than that of the matrix. The synergistic damping effect caused by the porous structure and a large number of interfaces between particles in the particle layer improve the damping capacity of the composites. [ABSTRACT FROM AUTHOR]

• Effect of rotational speed on damping capacity of pure Al is studied via FSP. • The hardness of FSPed Al is reduced due to decrease in dislocation density. • Frequency damping capacity of FSPed Al is reduced due to decrease in dislocations. • FSPed Al showed higher damping capacity at high temperatures due to grain refinement. An attempt is made here to understand the role of tool rotational speed on the damping capacity of friction stir processed (FSP) commercial pure aluminium metal. The as-received metal plates were processed with a conical pin tool by keeping the tool traverse speed as constant and varying the rotational speed 600, 900 and 1200 rpm. Subsequently, samples extracted from the stir-zones were characterized for their microstructure, hardness, frequency-dependent and temperature-dependent damping capacities. The increase in rotational speed decreased the dislocation density and increased the average grain-size at the stir-zone, thus significantly influenced the damping capacity. The frequency-dependent damping capacity decreased with rotational speed owing to the reduction in dislocation density. High-temperature damping was significantly higher for the processed samples, but at the same time increase in rotational speed decreased the damping as there was an increase in grain size. [ABSTRACT FROM AUTHOR]

• The CrMnFeCoNi-based MLGs composites were prepared by MA and SPS. • The MLGs content has a significant effect on the mechanical properties of composites. • The new damping source keeps the damping capacity of composites at a high level. The CrMnFeCoNi-based composites with different multi-layer graphenes (MLGs) content (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%) were prepared by powder metallurgy. The effects of the MLGs content on the mechanical and damping properties of the composites were studied specifically. The strength and hardness are obviously improved, and the tensile strength can reach 762 MPa. With the addition of MLGs, new damping mechanisms including the intrinsic damping of graphene and the interface damping are introduced, which lead the damping properties of composites to remain at a high level. As the content of MLGs increases, the Maximum internal friction (Q-1 max) of the composites increases first and then decreases, and its maximum value is 0.0667. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the interface structure between the matrix and the particle on the damping capacity was investigated using Mg–Zn and Mg–Zn–Y alloys in this study. The damping capacity was not affected by the interface structure at room temperature. However, the onset of temperature, which was higher in the Mg–Zn–Y alloy than in the Mg–Zn alloy despite their similar grain sizes, increased the damping capacity through grain boundary relaxation by grain boundary sliding. Compared to the Mg–Zn alloy, the existence of the quasicrystal phase particles, which had the coherent interface with low interface energy, was likely to have suppressed and delayed the grain boundary sliding in the Mg–Zn alloy. [Copyright &y& Elsevier]

Abstract: Internal friction measurements were conducted to examine the damping behavior of a porous Cu–11.9Al–2.5Mn (wt.%) shape memory alloy. It is found that the internal friction background significantly increased with increasing volume fraction or decreasing diameter of the pores due to stress concentration and mode conversion around pores when loaded, the refined microstructures and increased dislocation population. [Copyright &y& Elsevier]