Grain boundary damping in substitutional alloys

A study was made of the grain boundary damping characteristics of twelve Cu?Ni alloys, chosen to cover the entire range of solid solutions. The height, temperature, and activation energy of the solute peak was used to investigate solute segregation to grain boundaries. A criterion was developed to determine solute build up in the grain boundaries, and when applied to other alloy systems, it verified the well known equilibrium segregation concept due to Mclean.¹² The qualitative model for the low temperature peak in fcc pure metals¹⁰ was modified to incorporate segregation effects and thus explain the origin of the solute peak in dilute alloys. The model explained, without modification, the behavior of a concentrated alloy, as long as it was a complete solid solution.     

Effect of Ho-doping on microstructure and magnetostriction of TbDyFe alloys

Tb0.3Dy0.7HoxFe1.95 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50, 0.65) quaternary alloys were prepared by arc-melting and followed by annealing. The phases present and structure of the alloys were determined using a D8-Advance X-ray diffractometer. The magnetostriction of the alloys was studied by standard strain gauge technique. The dependence of Ho content on the structure, magnetostriction and density of the alloys was investigated in detail. The research results showed that Ho-doping did not change MgCu2-type cubic Laves structure in Tb0.3Dy0.7Fe1.95. When Ho content x≤0.2, rich rare earth phase presented in the alloys increased and magnetostriction of the alloys reduced evidently with increasing x, but for alloys with x>0.2, the content of rich rare earth phase started to reduce and the magnetostriction increased quickly, especially at low magnetic field in the alloy with x=0.65 due to separation of rich rare earth phases on the surface of the alloy.     

Effect of copper on magnetostriction and mechanical properties of TbDyFe alloys

The intrinsic brittleness of the TbDyFe alloy significantly decreases its mach inability and applications.This paper aims to improve the toughness of TbDyFe alloy by adding Cu. Various alloys of the type(Tb_(0.3)Dy_(0.7))_(0.37)Fe_(0.63-χ)Cu_χ(χ=0, 0,01.0.03, 0.05, 0.08, 0.1) were fabricated by an arc melting furnace under a high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance were studied systematically. The results show that the (Tb,Dy)Cu phase forms in these alloys upon the addition of Cu. Correspondingly, their toughness improves, attributed to the formation of a (Tb,Dy)Cu phase. Compared to the Cu-free alloy, the fracture toughness (Kic) increases 2-3 times with increasing Cu content. However, the magnetostriction performance of these alloys declines with Cu addition, due to the low-magnetic performance of the (Tb,Dy)Cu phase at room temperature. Compared with other alloys, the alloy with the addition of 1at%Cu shows the best compromise between the saturation magnetostriction and fracture toughness.     

Use of damping alloys to fight noise

Moscow Institute of Steel and Alloys. Translated from Metallurg, No. 2, p. 26, February, 1994.     

Research on microstructure and magnetostriction of Fe83Ga17Dyx alloys

The crystal structure, microstructure and the magnetostriction of Fe₈₃Ga₁₇Dy_x (x=0, 0.2, 0.4, 0.6) series alloys were studied. The results showed that the influence of the Dy on the crystal structure of the alloy was very small but the effect on the microstructure was significant when different contents of Dy were added into the Fe₈₃Ga₁₇ alloy, respectively. Meanwhile, the magnetostriction of Fe₈₃Ga₁₇Dy_{0. 2} alloy was greatly enhanced, the magnetostriction λ value reached 300×10^?6 at 400 (kA/m) magnetic field.     

Stress-strain hysteresis and damping in MnCu and NiTi alloys

Uniaxial stress-strain hysteresis loops for high damping manganese-copper (MnCu) and nickel-titanium (NiTi) shape memory alloys are experimentally determined. The characterization concerns two MnCu samples, one containing 60 pct Mn, the other 40 pct Mn, and two NiTi samples, one in the martensitic phase and the other in the austenitic phase at room temperature. In the 225 to 360 Hz frequency range, tests are conducted using a vibration exciter; for lower frequencies (2Hz), we use a Material Test System (MTS) servohydraulic apparatus. The ensuing characterization allows us to compute the energy dissipated per unit volume per cycle, the dynamic modulus, and the loss factor as a function of frequency and strain amplitude. The sensitivity of these results to such factors as frequency, temperature increments during the tests, and vibration duration are discussed. The experimental stress-strain characterization is also used to express the tangent stiffness along the stress-strain path as an analytical function of strain (within the vibration cycle) and strain amplitude using kriging interpolation. Behavioral differences both between the alloys and also from equivalent linear viscous models are discussed.     

Characterization of the damping properties of die-cast zinc-aluminum alloys

Characterization of the mechanical damping properties of a series of die-cast zinc-aluminum alloys is described. Over the range of variables (temperature, frequency, and vibration strain amplitude) normally encountered in service applications, it is shown that the damping consists of two components. Both components are due to linear relaxation mechanisms: the first is a thermoelastic relaxation and the second is the low-temperature tail of a broadened boundary relaxation. Some of the alloys exhibit elevated damping levels over a useful frequency range, particularly at the temperatures encountered in under-hood applications in automobiles. This paper is based on a presentation made in the symposium “Acoustic/Vibration Damping Materials” presented during the TMS Fall Meeting, Indianapolis, IN, October 1–5, 1989, under the auspices of the TMS Physical Metallurgy Committee.     

Use of alloys with good damping properties in the fight against noise

Moscow Institute of Steel and Alloys. Translated from Metallurg, No. 7, p. 28, July, 1994.     

Effect of preferred orientation on the damping capacity of magnesium alloys

The torsional vibration damping of Mg-4.5 Ce alloys has been correlated with the texture orientation resulting from the method of fabrication. Forged and forged-plus-swaged alloys at vibratory stress levels of 1500 psi exhibit specific damping capacities, respectively, of 6 and 11 times that of an extruded alloy of similar composition. Pole figures show that the basal planes are oriented preferentially in the extruded alloys with a 20 deg tilt to the axis of the extrusion, while the basal planes are generally parallel to the rod axis for forged or forged-plus-swaged alloys. The correlations indicate that the major source of damping in these hexagonal magnesium alloys is stress-induced anelastic shear on the basal planes (probably by dislocation motion).     

X-ray diffraction analysis by Rietveld refinement of FeAl alloys doped with terbium and its correlation with magnetostriction

Fe₈₁Al₁₉ polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal direction.Microstructural examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 phase.As a consequence of doping with Tb,the lattice ...     

The effect of carbon on the loss of room-temperature damping capacity in copper-manganese alloys

A high damping Cu-Mn alloy with a nominal composition of 48Cu-48Mn-1.5Al-0.27Si-0.072Sn-0.028C-0.05Er (all compositions in wt pct) was studied to determine the mechanism of the loss of damping capacity during room-temperature storage. In this study, it was found that an Er-modified alloy sample that was artificially aged for 16 hours at 400 °C was stable even after 68 weeks of room-temperature storage. However, a loss of damping capacity was exhibited in the same material when aged to produce an underaged or peakaged condition. The decrease in damping capacity was found to be thermally activated with at least three relaxation processes. Each of the three relaxation processes appear to be related to the diffusion of carbon within the Mn-rich regions and a single activation energy of 0.970±0.05 eV was used to model these processes. Rapid loss of damping capacity was observed in the same alloy when doped with excess carbon. After 3 weeks of storage at room temperature, the damping of the carbon-doped material, artificially aged at 400 °C for 4 hours, was reduced to one-third of its initial damping capacity.     

添加Si对FeMn阻尼合金组织及性能的影响

采用倒扭摆测试仪、SEM、TEM等方法研究了添加Si对FeMn阻尼合金组织和性能的影响.结果表明,Si的加入增加了FeMn合金的层错和ε马氏体片层的数量,但由于马氏体片的交叉及Si引起的晶格畸变都阻碍了合金阻尼源界面的移动,使得合金阻尼性能降低;预变形后Fe-19Mn合金阻尼性能呈现先增加后降低的趋势,而Fe-19Mn...     

Use of damping alloys based on iron to reduce noise from impacts

Iron-based alloys (steels) with superior damping properties have been developed. Use of the new alloys reduces noise by 6–8 dB compared to well-known standard steel 45.     

TbDyFe超磁致伸缩材料机电耦合特性实验研究

主要讨论TbDyFe超磁致伸缩材料电磁与机械耦合特性实验的若干问题,建立了电磁与机械耦合系统的物理模型并应用阻抗分析方法得到了相应的等效电路．设计制作了实验装置,测定了在电磁场与应力场共同作用下TbxDy1-xFe2-s三元稀土合金超磁致伸缩棒的机电耦合系数与电磁与机械耦合系统振动频率等．所得结果为进一步研制稀土超磁致伸缩换能器提供了重要的实验依据．