In this work, an Al-Zn eutectoid damping alloy with a nominal composition of 50Al-489Zn-1Ti-01Ce (at

The five Fe3CrxMn2CoAl0.5 high entropy damping alloys with different Cr molar ratios were prepared by vacuum arc melting technology, and their microstructures, damping capacity, and mechanical properties were systematically investigated. The results show that as the Cr molar ratio increases, the high entropy damping alloy undergoes a microstructural transition: a single FCC phase (x = 0.5) evolves into a duplex FCC+BCC mixture (x = 0.8) and finally stabilizes as a single BCC structure (x >= 1.4). The FCC phase solidifies as primary dendrites, whereas the BCC phase precipitates as polygonal, equiaxed grains. Continuous FCC films wet the BCC boundaries in the Cr1.1 alloy, but this film is no longer visible in Cr1.4 and Cr2.0 alloys. Owing to the preponderance of BCC, the Cr1.1, Cr1.4 and Cr2.0 alloys exhibit significantly higher damping capacity than the FCC-dominated Cr0.5 and Cr0.8 alloys. A progressively larger absolute volumetric magnetostriction coefficient accompanies the rise in Cr content (x >= 1.1), while the magnetic domain morphology evolves from closed/dagger domains to fine dendritic domains, both of which amplify energy dissipation and damping. The 0.2 % compressive yield strength climbs to a maximum of 1218.3 MPa at x = 1.1 and then declines with further Cr addition. Benefiting from the exceptional ductility of the FCC matrix, the Cr0.5 and Cr0.8 alloys sustain compressive strains exceeding 60 % without fracture, attaining markedly higher compressive stresses of 2153.6 and 2640.9 MPa. Conversely, the BCC-dominated alloys (x = 1.1-2.0) suffer from intrinsic brittleness, the fracture strains decrease monotonically, while their ultimate compressive strengths fall in parallel.

The microstructure and properties of Fe17Mn and Fe17Mn0.1C0.4Ti (i.e. FM and CTi) alloys were studied comparatively. Some fine TiC particles are precipitated within CTi alloy and the sizes of y-austenite and c-martensite phases are reduced by adding trace C and Ti. The y 1/4 c transformation temperature decreases while the content of c phase increases with C and Ti additions. In addition, the CTi alloy possesses higher strain energy storage, lower stacking faults probability, more strong and weak pinning points, resulting in a lower damping capacity compared to FM alloy. Although CTi alloy exhibits lower damping capacity than FM alloy, the addition of C and Ti reduces the annealing temperature and time to achieve the optimal damping capacity. The additions of C and Ti significantly enhance the tensile strengths, with the highest values achieved for both alloys after annealing at 900 degrees C for 1 h, reaching 699.5 MPa for FM alloy and 819.1 MPa for CTi alloy.

The damping mechanism of Mn-Cu based alloys is usually ascribed to the antiferromagnetic transition and subsequent FCC-FCT martensitic transformation which take place in spinodal Mn-rich regions. In the present work, we investigate the influence of Ti substitution on the spinodal characteristics in the Mn-Cu based alloys subjected to ageing treatments. The experiments of X-ray diffraction (XRD), internal friction (IF) examination, transmission electron microscope (TEM) and mechanical spectrum characterizations were performed. The results highlight that the appearance of the Cu clusters enhances the Mn content in neighboring regions. Moreover, the Ti addition can promote the element diffusion, thus the damping capacity of the 0.2Ti alloy is the highest in the Mn-Cu based alloys.

The joints between medium carbon (MC) steel and Mn-Cu alloy were prepared by TIG arc-brazing process. However, intermetallic compounds (IMCs) precipitating along interfaces are detrimental to the mechanical strength of arc -brazed Mn-Cu/MC steel joints. In this paper, a minimal amount of Zn was added in fillers to prohibit the growth of IMCs. Both of the mechanical properties of the joints and microhardness across the joint section were measured. Scan electronic microscope (SEM) was used to observe the fractural morphologies of the joints and the IMCs characteristics near the interface of MC steel side. An X-ray diffraction (XRD) method was used to analyze the phase constitutions of IMCs in the fracture surface. The results show that the IMCs consist of both of reaction intermetallic compounds (RIMCs) and growth intermetallic compounds (GIMCs). Moreover, the minimal Zn addition in fillers prohibit the growth of the RIMCs and GIMCs and consequently improve the mechanical properties of the joints.

Herein, the behaviors of CdSnN 2 are computationally investigated under uniaxial compressions based on density functional theory (DFT) calculations and a DFT‐1/2 scheme. When the compression is in [100] direction, phase transition is observed from Pna2 1 to Pnma phase when the compression is larger than 30 GPa, while no phase change is observed for uniaxial compressions along [010] and [001] directions. For the former one, the bandgap first increases with a maximum at 20 GPa, followed with a reduction upon the critical pressure and nearly a constant above 30 GPa. The bulk modulus nearly increases monotonically except for the transit region from 20 to 29 GPa, and the shear modulus decreases to 29 GPa and then increases for Pnma phase. When compression is along [010] direction, the bandgap nearly remains around 0.620 eV. The bulk modulus increases with a maximum around 25 GPa and then decreases, while the shear modulus monotonically decreases. The bandgap first increases and then shrinks monotonically with increasing compression in [001] direction. The bulk modulus monotonically increases and the shear modulus decreases. The absorption is then calculated and discussed. The anisotropic behaviors of CdSnN 2 may hence indicate some potential applications.

The effects of temperature and strain rate on the deformation microstructure and hardness of Al-Zn eutectoid damping alloy was systematically investigated. The results show that the deformed alloy is mainly composed of eutectoid structure with eta-Zn distributing on alpha-Al matrix. There are two forms of eta-Zn particles in the eutectoid structure of the deformed alloy. The first type of eta-Zn particles (eta-Zn-I) have relatively large sizes and display irregular morphology; another type of eta-Zn particles (eta-Zn-II) have relatively small sizes and are characterized by dispersion distribution. There exist predominant eta-Zn-I particles at lower temperature and higher strain rate while dominant eta-Zn-II particles at higher temperature and lower strain rate. The hardness of the Al-Zn eutectoid damping alloy shows an overall rising trend with increase in temperature and decrease in strain rate. In particular, the highest hardness values (up to 113.07 HB) are obtained at 648 K/0.01 s(-1).

Four Al-Zn eutectoid damping alloys with nominal compositions of 50Al-(49.9-x) Zn-xTi-0.1Ce (x=0, 0.5, 1 and 2 respectively) (atomic percentages, at.%) were prepared by hot extrusion following the resistance and induction melting and homogenization. The effects of Ti content on the microstructure, mechanical properties and damping capacity of Al-Zn eutectoid damping alloys were investigated. The results show that the eutectoid structure in the alloy is refined first and then coarsened with increase in Ti content (1Ti alloy has the finest eutectoid structure), and a small amount of (Al, Zn)3Ti intermetallic blocks are observed in the 2Ti alloy. There exist two types of regions for the eutectoid structures in the four alloys, region Ⅰ has nearly granular morphology and relatively large phase sizes, and region Ⅱ has very fine lamellar structure (the lamellar spacing is only 50-80nm in 1Ti alloy). With the increase of Ti content, the area percentage of region II exhibits an increasing trend. The tensile property of the alloy is ameliorated by Ti addition, and the tensile strength increases first and then decreases with the increase of Ti content. In particular, 1Ti alloy has a high tensile strength of up to 390MPa, which is increased by 49.43% compared to that of 0Ti one. The damping capacity of the alloys is improved by proper addition of Ti (tan δ values of 0.5Ti and 1Ti alloys increase by 78.26% and 26.09%, compared to that of 0Ti one), while is not changed obviously by further addition of Ti (up to 2at.%).

As a metal functional material, the Mn-Cu-based alloys are regarded to be able to cope with the vibration and noise from machines. In particular, the as-cast alloys often exhibit an excellent damping capacity, which is attributed to the Mn segregation in the alloys. Herein, to amplify the kind of segregation, a trace of Sn is added in as-cast Mn-Cu-Al alloys. The phase structures of the as-cast Mn-44Cu-1.5Al alloys are analyzed in detail through X-Ray diffraction (XRD). The distribution characteristics of face-centered cubic (FCC) phases and face-centered tetragonal (FCT) phases are observed using electron backscatter diffraction (BSE). The alloys' dynamic mechanical spectra and internal friction (IF) are measured using an inverted torsion pendulum device. It is found that the addition of Sn promotes the Mn segregation in the as-cast Mn-44Cu-1.5Al alloys. A large amount of FCT phases appears in the dendritic trunks, enhancing the damping capacity of the alloys. In the meantime, the Sn atoms enhance the twin boundary mobility in Mn-rich dendritic trunks. As a result, the alloy containing 1wt% Sn has the highest damping capacity in the alloys.

Mn-Cu合金是一种特殊的金属功能材料,能够依靠相界及孪晶界的相对运动耗散振动能量,实现结构的减振降噪.合金元素是影响Mn-Cu合金相变的主要因素之一,但合金元素Sn对合金相变机制的报道却很少.本文以Mn-44Cu-1.5Al以及Mn-43Cu-1.5Al-1Sn阻尼合金为研究对象,通过扫描电镜(SEM)分析了两种合金的成分分布特征;利用电子背散射衍射(EBSD)分析了合金内相的分布情况;利用X射线衍射(XRD)分析了合金的相结构差异;通过多功能内耗仪测试了两种合金的相变点,阻尼性能及其不同激振频率下合金的动态力学谱.结果表明,由于Sn的添加,合金的阻尼性能从0.0142提高至0.055(扭转振幅为2×10-4).其根本原因是Sn元素一方面将合金的马氏体(fct)相变点提高了60.3℃,使合金中的fct相转变量显著增加,从而有效提高了合金组织的相界面积;另一方面,固溶的Sn元素降低了孪晶激活能,增强了合金的孪晶弛豫行为,且相比于0Sn合金,在5～10Hz范围内1Sn合金的激活能降低了42.71％.此外,由于Sn的原子半径较大,Sn元素进入基体时会提高晶格畸变度从而更有利于马氏体的生成,这使得马氏体相主要分布在晶界附近的富Sn区.研究将有助于理解合金化在Mn-Cu合金阻尼机制中的重要作用.

A damping alloy with a nominal composition of 50Al-49.9Zn-0.1Ce (at%) was tested in hot compression (60% depression) using a Gleeble-3800 thermomechanical simulator at deformation temperatures and strain rates ranging from 573 to 648K and 0.01 to 10 s(-1), respectively. According to the true stress-strain curves, two constitutive equation models based on peak stress and strain compensation were constructed. The microstructure of the alloy after deformation was characterized and analyzed by means of X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the flow stress increases with decreasing deformation temperature and increasing strain rate. The theoretical predictions of the constitutive equation model at low temperature and high strain rate are well fitted to the measured values with low average absolute relative errors. At low strain rates and high temperatures, the alpha + eta eutectoid structure tends to transform from lamellar to granular morphologies, which is accompanied by the increased sizes of alpha and eta phases. Also, the obvious dissolution of eta into alpha phase has been occurred and some tiny holes induced by thermal-force coupling have been formed during compression. In this work, the Al-Zn-Ce damping alloy is more suitable for thermomechanical processing at relatively lower temperatures and meanwhile higher strain rates (such as at 573K/0.1 s(-1), 573K/10 s(-1) and 623K/10 s(-1)).

采用井式电阻炉熔炼及真空感应熔炼的方法制备名义成分为50Al-48.9Zn-1Ti-0.1Ce(原子百分数,at%)的合金,然后在380℃保温20h进行均匀化处理,并于150℃下分别进行1 h、2 h、4 h、6 h,10 h的时效处理,研究了均匀化及时效处理对Al-Zn共析阻尼合金组织和性能的影响.结果表明:均匀化处理消除了原铸态组织中的枝晶偏析,此时合金主要由α-Al分布在η-Zn基体上的共析组织所构成.然而经不同时间时效处理后的合金则主要由η-Zn分布在α-Al基体上的共析组织所构成.随着时效时间的增加,α-Al相含量逐渐增加(在均匀态下以及时效1 h、2 h、4 h、6 h、10 h后α-Al相的面积百分数分别约为16.1%、40.3%、47.2%、54.7%、60.1%、68.2%),共析组织不断粗化,且其形貌逐渐从不规则片层或颗粒状向近似等轴的颗粒状而转变.随着时效时间的延长,Al-Zn共析阻尼合金的阻尼性能不断上升(对于时效10h后的合金试样,当应变振幅为8×10-4时,其tanδ的值约为0.052).与均匀态下的合金相比,短时时效处理后Al-Zn共析阻尼合金的拉伸性能明显改善拉伸性能(在时效 1h时获得最高拉伸强度,其σb 值约为197.6 MPa),但随着时效时间的进一步延长,合金抗拉强度呈现逐渐下降的趋势.

母材与钎缝界面处的金属间化合物会降低MnCuAl阻尼合金与430不锈钢钎焊接头的结合强度,进而降低焊接结构的使用性能.采用在430不锈钢表面电镀Ni层后再进行钎焊的方法对有害的金属间化合物进行抑制,同时探究不同厚度Ni层对接头组织、金属间化合物的影响规律和机理.结果表明,镀Ni层与基体界面处无明显缺陷,镀Ni层能够与430SS母材良好结合.对于钎焊接头,未镀Ni时,在430SS侧界面处分布着γ-(Fe,Mn)固溶体层,在两侧的反应层与钎缝中心区之间均存在连续分布的IMC,且伴随着钎剂残留;电镀8μm Ni层时,焊后镀Ni层完全溶解,在430SS侧界面处仍分布着γ-(Fe,Mn)固溶体层,但接头中金属间化合物消失,且只有极少数钎剂残留;镀层为20μm时,焊后在430SS侧有一层残余镀Ni层,未发现γ-(Fe,Mn)固溶体层,金属间化合物消失,且未见钎剂残留.分析认为,当镀层厚度分别为8μm、20μm时,Ni层分别是通过合金化作用、阻隔作用抑制了金属间化合物的生成.

A Fe-16Cr-2.5Mo(wt％)damping alloy was prepared by spark plasma sintering(referred to SPS alloy)and vacuum induction melting followed by forging and annealing(referred to VIMFA alloy).The comparative study on microstructure,magnetic performance,damping capacity and mechanical property of SPS and VIMFA alloys was conducted.Results show that the relatively high compactness of SPS alloy is obtained.The dissolution of Cr and Mo in a-Fe solid solution is obviously promoted and the homogeneity of microstructure of SPS alloy is dramatically ameliorated with increase in sintering temperature and extension in holding time.SPS alloys exhibit relatively lower saturation magnetization but higher coercivity than VIMFA ones.There is still favorable damping capacity for SPS alloys despite it is lower than that of VIMFA one.Furthermore,the damping capacity of SPS alloy slightly rises with increase in sintering temperature and extension in holding time.The SPS alloys possess evidently higher compression strength than VIMFA ones.Also,the compression strength of SPS alloy rises with increase in sintering temperature.

Abstract Mn–Cu alloys are metal materials, which can be used to reduce vibration and noise from machines. With their inner damping mechanism, the alloys show an excellent damping capacity. However, previous reports show that the damping capacity of the alloys often attenuates after placing at room temperature (RT) for a long time. In the present study, the as-cast Mn–Cu–Al–0∼3 wt% Sn alloys were held at RT for 18 months. Their crystallization morphology was observed using backscattered electron (BSE) technology. The phase distribution was characterized using electron backscatter diffraction (EBSD). Their phase structure was analyzed by using X-ray diffraction (XRD). Their starting martensite transformation temperature (Ms) and damping capacity were measured by using an inverted torsion pendulum device. It is observed for the first time that the FCT phases mainly form in the dendrites. With vacancies diffusing towards boundaries of phases and twins, the boundaries are pinned and the Ms point declines. Hence, the damping capacity attenuates within 18 months. Moreover, the addition of Sn can weaken the decline trend of Ms point and consequently the IF value of the Sn-contained Mn–Cu alloys attenuates less than that of the none-Sn alloy. This research could help us to understand how to cope with the damping attenuation of the Mn–Cu alloys.

Mo0.5NbHf0.5ZrTiAl, Mo0.5NbHf0.5ZrTiSi0.5Al and Mo0.5NbHf0.5CrZrTiAl (molar ratio) refractory high entropy alloys (RHEA) were prepared by vacuum arc melting. The influences of Si and Cr on microstructure and properties of RHEA were investigated. Three RHEA all contain BCC1 phase. Si addition promotes the formation of M5Si3 intermetallic compound, and the microstructure of Si0.5Cr0 RHEA consists of M5Si3 blocks and BCC1 + M5Si3 eutectics. Cr addition leads to the formation of Cr2Nb type Laves phase, and two BCC dendrites exist in Si0Cr RHEA. The compressive strength of Si0.5Cr0 and Si0Cr RHEA increased by about 102% and 85%, respectively, compared to Si0Cr0 one. The oxidation resistance of RHEA is improved by adding Si while dramatically degraded by adding Cr.

Three refractory high entropy alloys (RHEAs) with nominal compositions of Mo 0.5 NbHf 0.25 CrZr x TiAl (x = 0, 0.5, 1, mole ratio) were prepared by vacuum non-consumable arc melting technology. The influences of Zr addition on the microstructure, compressive performance and oxidation resistance at 1473 K of RHEAs were investigated and evaluated integrally. The results show that the three RHEAs are all composed of BCC1, BCC2 and Laves phases. With increasing the Zr content, the microstructure of RHEA has gradually become BCC1 + BCC2 eutectics, and also the area fraction of BCC2 phase exhibits a rising trend. Both peak stresses are displayed at the strains of near 0.03 and 0.08 respectively in the compressive stress-strain curves of the three RHEAs. On the whole, the compressive yield strength of RHEA shows an increasing trend with Zr addition. The oxide scales of the three RHEAs all possess good adhesion and obviously layered structures. The different oxidation products are distributed in their oxide scales and internal oxidation zones. The oxidation resistance of RHEA is dramatically degraded due to the decreased compactness of the oxide scale with Zr addition.

用Cu-34Mn-6Ni-xSn(x=6、8、10 wt％)钎料,对MnCuAl合金/430SS钢进行高频感应钎焊,表征接头组织、各区域显微硬度、接头剪切强度,并分析钎料成分对组织和力学性能的影响.结果表明,钎料中Sn含量会引起钎缝宽 度、MnCuAl合金侧部分润湿区域的形貌和宽度、钎缝中心区硬度发生变化.6Sn、8Sn钎料焊后钎缝宽度基本一致,而10Sn钎缝宽度明显减小;6Sn、8Sn和10Sn钎料焊接后部分润湿区的宽度分别为0、200、460 μm;钎缝中心区的平均硬度由6Sn至10Sn逐渐升高,与钎料本身的硬度变化一致.6Sn、8Sn和10Sn钎焊接头的剪切强度分别为320、307、293 MPa,断裂形式均为混合型断裂,裂纹贯穿MnCuAl合金侧的IMC层和钎缝中心.

Ferromagnetic Fe-Cr alloys can be used to reduce unwanted noise and vibrations because of their high damping capacity which is attributed to the irreversible magnetic domain-wall movement. However, excessive annealing usually causes an obvious drop of damping capacity of the alloys. In the present study, the magnetomechanical hysteresis effect (MMHE) is investigated by measuring magnetostriction coefficients of the annealed Fe-16Cr-2.5 -3.5Mo alloys. It is found that the annealing more than 1 h at 900celcius causes the attenuation of MMHE. The higher Mo concentration restrains the MMHE attenuation and the damping decline due to the MMHE attenua-tion. The research could help us to better understand the alloying role in the damping mechanism of Fe-Cr based alloys.

In this work, we presented laser welding-brazing of Al/steel dissimilar alloys with alternating magnetic field augmentation. Interfacial microstructures, element distribution and mechanical properties of the joints welded at different magnetic field frequencies were carefully investigated. Formation mechanism of HAZ cracking was also discussed. The results showed that Zn element in the filler metal promoted the occurrence of Fe-2 (Al, Zn)5 phase instead of Fe-Al intermetallic compounds at the steel interface, which greatly improved interfacial performance. Columnar crystals at the Al interface were broken into fine dendrites with the aid of the electromagnetic force in the molten metal. Zn-rich products at grain boundaries weakened the cohesions between grains and increased the crack susceptibility. It has been also found that formation of HAZ cracking mainly goes through four stages involving crack inoculation, crack nucleation stage, crack initiation and crack growth. The tensile force and elongation of welded joints subjected to an alternating magnetic field can be increased by 126% and 144%, respectively, compared to that of joints laser welded in the shortage of a magnetic field. Significant improvement in joint performance is attributed to the precipitation of Fe-2 (Al, Zn)5 phase and transformation of interface shape.