NON-LINEAR INTERNAL FRICTION PHENOMENA ASSOCIATED WITH FLOWING AND CRACKING OF ADHESIVE IN MARX METHOD

定量研究了Marx法测量低内耗试样内耗及模量亏损时各种粘结剂引起的所谓操作效应。对于水杨酸苯酯,水玻璃混合剂之类弱粘结剂所造成的背景内耗既不能忽略也不是常数,它与粘结层温度、热应力、时间、干燥程度和应变振幅等因素有关。经过高温热循环,粘结剂中出现徽裂缝时呈现双共振峰。在稍高频率的反常共振峰所测得的内耗,随应变振幅或大振幅激发时间的增加而减小,并且在小振幅时效中增大。当反常共振峰频率与正常共振峰靠近时,在内耗-振幅或内耗-时间图上呈现峰值效应。观察到各种共振振幅-频率滞后回线,在一定非线性回线和时效场合下观察到可重复的试样振幅的概周期跳动。 采用高温高强度粘结剂后,上述现象均消失,但是热应力使石英传递棒开裂或试样范性变形。 分析了Marx法的适用范围及改进途径。     

Experimental study of the nonlinear internal friction peaks in Al–Mg solid solutions

Nonlinear internal friction peaks associated with the interaction between dislocations and point defects are experimentally studied in cold-worked Al–Mg solid solutions. It is found that the appearance of these peaks is very sensitive to the cold-work methods among which the stretching method in the strain range of several percent is effective for reproducing the peaks. A maximum of the internal friction vs. strain amplitude at a given temperature around the peak is observed. With the forced vibration method and by using a nonlinear fitting program to subtract the background, the activation energies are measured to be 1.3, 1.1 and 0.7 eV, respectively, for the three peaks (P_L1, P₁′, P₁″) in the order of ascending temperature.     

INTERNAL FRICTION OF HYDRIDE PRECIPITATION IN Ta-H ALLOYS

测量了冷加工的高纯Ta丝在电解加氢前后的低频内耗。发现在加氢后除出现氢化物沉淀峰外,氢一位错交互作用的内耗峰也降低,附加范性扭形变对沉淀峰有明显的增强作用;在氧原子可动的温度范围内时效,可以完全消除形变对沉淀峰的增强作用。结果表明,氢化物可能择优在位错上沉淀。沉淀峰的本质可能与位错-氢化物交互作用有关。     

Mechanical spectroscopy of Al-Mg alloys

The internal friction of deformed, annealed, and quenched Al-Mg alloys with Mg contents of 0–12 wt % has been studied as a function of temperature. The measurements have been performed in the range of 25–580°C at 0.3–30 Hz using a DMA Q800 TA Instruments dynamic mechanical analyzer at the maximum amplitude of deformation ?₀ = 5 × 10^?5. In annealed alloys with Mg contents up to 5 %, a relaxation IF peak with activation parameters (activation energy H ≈ 1.7–2.1 eV) has been detected. In alloys with 8–12% Mg, this relaxation peak is absent and, at a lower temperature, another IF peak appears (with an activation energy H of about 1 eV), which is interpreted as the Zener peak in terms of the combination of activation parameters. The article discusses the nature of these peaks and the influence of alloying on the relaxation mechanisms. In cold-worked alloys, an IF pseudo-peak takes place, which is related to the recrystallization of samples, and its temperature position in the alloys that contain more than 5% Mg depends not only on the degree of deformation, but also on the dissolution temperature of the β phase.     

非线性滞弹性内耗的实验和理论研究

本文评述了非线性滞弹性内耗研究的新近发展，非线性滞弹性内耗与线性滞弹性内耗的主要区别是它不但呈现频率内耗峰和温度内耗峰，还在出现温度内耗峰的温度范围内出现振幅内耗峰。自１９５０年首次发现非线性滞弹性内耗现象以来，截至目前，已经发现了两种呈现非线性滞弹性内耗的体系：（１）点缺陷（空位与溶质原子）与位错的交互作用，在这方面已有了丰富的实验结果，提出了有关的物理模型，也进行了一些理论研究工作，（２）位错     

SECONDARY CYCLIC HARDENING AND GRAIN BOUNDARY CRACKING IN HIGH PURITY Al

对充分退火的、晶粒尺寸超过10 mm的99.999％纯Al试样在Schenck试验机上进行了恒应变幅的对称拉-压疲劳试验。应变幅的范围从2.82×10~(-4)到6.1×10~(-3)。测量了各个循环之后的拉、压半周的峰值应力。在所用应变范围内,都观察到二次循环硬化,并在大约3.0×10~(-3)的应变幅处有一个最大值。 金相和电子扫描显微镜的观察表明,在高应变幅下,在晶界区域内产生不同的塑性应变,导致与穿晶裂纹联接的晶界滑动和迁移。在同一断裂面上存在不同型式的疲劳条纹。 作为简单的讨论。假定二次硬化是二次滑移和晶界滑动过程中局部硬化的结果。     

Microstructures and mechanical properties of welded Fe-12Cr-20Mn austenitic stainless steel

The effects of welding on the tensile and fatigue properties of fully annealed and cold-worked Fe-12Cr-20Mn austenitic stainless steel were evaluated. Room temperature and 500 °C tensile tests and room temperature cantilever beam fatigue tests were accomplished on specimens that contained autogenous bead-on-plate welds. The tensile and fatigue properties of the fully annealed material were not significantly influenced by welding. The tensile properties of the welded cold-worked material were also not significantly affected by the presence of a weldment. However, welding caused a large reduction of the fatigue life of the cold-worked material. Fatigue cracks preferentially initiated at large Mn-Si inclusions that formed in the fusion zones of the weldments.     

Effect of thermal aging on the temperature spectrum of internal friction of alloyed Fe-Si-Al-C ferrite

Snoek relaxation parameters in a quenched ternary Fe-Al-Si alloy have been studied during subsequent aging of samples. Substitutional atoms contribute to a broadening of the Snoek peak on the high-temperature side due to an additional relaxation induced by migration of carbon atoms, which interact elastically with the substitutional atoms. Upon subsequent heating (aging) to ～350°C, there occurs a decomposition of the oversaturated solid solution, which is accompanied by a redistribution of carbon atoms over different positions, which is seen from an analysis of the parameters of the Snoek peak. At temperatures about 400°C, there are observed anomalies related to the re-pinning of dislocations by interstitial atoms and to the formation of new internal-friction peaks.     

The internal friction peaks correlated to the relaxation of atomic defects in Fe47Al53 alloy

The internal friction behavior of a Fe₄₇Al₅₃ alloy was examined to understand the evolution of the atomic defects. It is found that the internal friction peak observed at around 410 °C is in fact composed of two relaxational peaks (P1 and P2) that shifted toward high temperature with increasing frequencies. The P1 peak originates from the stress-induced migration of Al antisite atoms between the vacancies while the P2 peak originates from the dissociation of the interstitial carbon atoms from the C–V complexes and subsequent diffusion.     

Influence of aging on damping behavior of TiNi/TiNi alloys synthesized by explosive welding

The influence of aging time, measuring frequency and strain amplitude on the internal friction of TiNi₅₁/TiNi_50.2 sandwich composite was investigated. The DSC and internal friction measurements were employed to characterize the sample. The two internal friction peaks of the specimen were confirmed corresponding to the reverse transformation of TiNi₅₁ and TiNi_50.2 component, respectively. The internal friction as a function of the temperature at different measuring frequencies was presented and it was found that the height of both internal friction peaks increased with decreasing frequency; however, the increase corresponding to TiNi_50.2 component was larger than that of TiNi₅₁ component. Furthermore, the internal friction of the TiNi/TiNi composite alloy decreased with increasing the measuring strain amplitude. The height of internal friction peak of TiNi₅₁ component increased with increasing the aging time, whereas that of the TiNi_50.2 component did not change significantly. The increase in internal friction of TiNi₅₁ appeared to be associated with the formation and growth of precipitate during the aging process.     

铸态Mn-Cu合金的马氏体相变内耗的研究

对含Mn量为90%的铸态Mn-Cu合金的马氏体相变内耗进行了研究.用低频测量时,稳定峰(变温速率T=0)的峰温与频率无关,峰高随f的增加而减小,因而不是静滞后型内耗.连续变温的相变峰高与T,f有关,但峰高Q_m~(-1)与T,1/f或T/f都不满足线性关系;在一定振幅范围内(A_ε:1×10~(-5)—1×10~(-4)),峰高与应变振幅基本无关.因而,认为低频变温马氏体相变内耗的大小与相变中共格界面有关,即马氏体相变内耗不仅有体积效应的贡献,而且有界面效应的贡献.     

EFFECT OF ORIENTATION ON STRESS RESPONSE,FRICTION STRESS AND BACK STRESS DURING CYCLIC DEFORMATION IN Al SINGLE CRYSTALS

The symmetrical push-pull fatigue tests at strain amplitude of 2×10~3 with different sliporientation of Al single crystals,were carried out at room temperature in air.The peakstresses of various cycles were measured and the stress-strain hysteresis loops for selected cy-cles were recorded.The energy losses.friction stresses,back stresses and shape     

Theory of the nonlinear internal friction associated with bulk diffusion of solute atoms around dislocations in Al–Mg alloys

In this paper the nonlinear (amplitude-dependent) internal friction (P₃ peak) in cold-worked Al–Mg alloys is theoretically studied by solving the bulk diffusion equations of the solute atoms (Mg atoms) under the action of dislocation drag. The results in the case of a constant external stress show that the bow-out distance of the dislocation has an exponential relation with time, which can be well described by an exponential creep function with a Gaussian distribution in τ. With the increasing strain amplitude, the relaxation strength Δ and relaxation time τ decrease, while the distribution parameter increases. Both activation energy H and pre-exponential factor τ₀ deduced from τ through Arrhenius relation are dependent on strain amplitude.     

Internal friction in steel EI961

Conclusion A strain maximum caused by reaction of dislocations with interstitial impurities was detected on curves of the temperature dependence for internal friction of hardened and tempered steel EI961 specimens in the region of 350°C.In studying the amplitude dependence of internal friction existence was established of sections of amplitude-independent and amplitude-dependent internal friction. Tempering leads to a reduction in the level of internal friction and a change in the critical amplitude for the changeover from amplitude-independent to amplitude-dependent internal friction.Voronezh Polytechnic Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, 62–64, February, 1990.     

Internal friction, dilatometric and calorimetric study of anelasticity in Fe-13 at.% Ga and Fe-8 at.% Al-3 at.% Ga alloys

This paper investigates the structural transitions associated with different cooling rates from a high temperature disordered state and the effect of substitution of Ga atoms by Al atoms in Fe-Ga binary alloys on the ordering processes. Two iron-based low carbon (about 0.04 at.% C) alloys Fe-13 at.% Ga and Fe-8 at.% Al-3 at.% Ga are studied. Internal friction, dilatometric and calorimetric tests are carried out to check ordering in these alloys and contribution of structural defects to relaxation spectrum. Several thermally activated internal friction peaks have been observed and their activation parameters evaluated by means of temperature and frequency dependent internal friction tests using forced vibration. For most of these peaks physical mechanisms are proposed. Apart from these thermally activated relaxation peaks, a structural, frequency independent relaxation takes place at 250-300 °C. Dilatometric and DSC curves show the appearance of a contraction effect in the same temperature range. This effect was studied in alloys cooled down with different cooling rates. We believe that the frequency independent internal friction peak (denoted as the P3 peak in this paper) and peaks at dilatometric and DSC curves are controlled by the same structural mechanism and therefore the activation energy for this anelastic mechanism is derived from DSC data.     

结晶状态对铜内耗频率谱的影响

用内耗频率谱仪测量了多晶铜、纳米晶铜和单晶铜试样的内耗频率谱，在170，320以及490Hz附近观测到3个明显的共振吸收频率峰，3种试样在晶粒结构上存在极大差别，但其共振吸收内耗峰出现在相同频率范围，这说明产生内耗频率峰的机制与晶体缺陷和晶粒尺度无关，而与材料的晶体点阵性质密切相关。     

Ta－O固溶体中的Snoek－K■ster弛豫

试样表面镀一薄层Ｔｉ，消除内耗测最过程中氧吸附的影响．在镀Ｔｉ的Ｔａ—Ｏ试样中详细研究了Ｓｎｏｅｋ—Ｋｏｓｔｅｒ弛豫．观察到了两个内耗峰（较低温度的ＳＫ１峰和较高温度的ＳＫ２峰）．考查之退火温度和氧含量对内耗峰的形状和稳定性的影响．ＳＫ１峰和ＳＫ２峰的激活能分别为１．４和２．１ｅＶ．用Ｓｅｅｇｅｒ的螺位错上的双弯结成核和迁移以及几何弯结的迁移理论解释了实验结果．通过理论和实验比较，得到的螺位错上双弯结形成能约为０．９ｅＶ，螺位错与氧原子的结合能约为０．３ｅＶ实验还发现，进一步冷加工对Ｓｎｏｅｋ峰的影响在实验误差范围内，可以略去不计．     

Contribution of phase and structural transformations to linear and nonlinear mechanisms of anelasticity in binary Al-Mg alloys

Effects of the processes of the recrystallization and precipitation of the β phase in Al-(0.3–12%)% Mg alloys on the mechanisms of grain-boundary relaxation and dislocation-induced microplasticity have been studied in some detail. The decrease in the dislocation density due to the process of recrystallization of cold-worked alloys leads to the formation of a pseudopeak in the curves of the temperature dependence of internal friction and to a decrease in the critical amplitude of deformation necessary to initiate dislocation motion in a stress field. The precipitation of the β phase in the structure suppresses the mechanism of grain-boundary relaxation; the dissolution of the β phase, which leads to the formation of impurity atmospheres, then to the passage of magnesium atoms into the solid solution, impedes dislocation motion. Depending on the total content of Mg in the alloy, the dislocation mobility upon the measurements of amplitude dependences of internal friction can be described in terms of either breakaway or friction models. The characteristics of grain-boundary relaxation and dislocation-impurity interaction and of their temperature dependences have been estimated quantitatively.     

Ta—O固溶体中的Snoek—Koster驰豫

试样表面镀一薄层Ｔｉ，消除内耗测最过程中氧吸附的影响．在镀Ｔｉ的Ｔａ—Ｏ试样中详细研究了Ｓｎｏｅｋ—Ｋｏｓｔｅｒ弛豫．观察到了两个内耗峰（较低温度的ＳＫ１峰和较高温度的ＳＫ２峰）．考查之退火温度和氧含量对内耗峰的形状和稳定性的影响．ＳＫ１峰和ＳＫ２峰的激活能分别为１．４和２．１ｅＶ．用Ｓｅｅｇｅｒ的螺位错上的双弯结成核和迁移以及几何弯结的迁移理论解释了实验结果．通过理论和实验比较，得到的螺位错上双弯结形成能约为０．９ｅＶ，螺位错与氧原子的结合能约为０．３ｅＶ实验还发现，进一步冷加工对Ｓｎｏｅｋ峰的影响在实验误差范围内，可以略去不计．     

Mechanical spectrum and oxygen vacancies in γ-Na0.66CoO2

The mechanical spectrum of γ-Na_0.66CoO₂ below room temperature was measured using the vibrating reed method at kilohertz frequencies. In the cooling process, internal friction is less temperature dependent above 240 K and shows a continuous decrease with the decrease in temperature below 240 K in annealed γ-Na_0.66CoO₂ sample. A transition was suggested to occur around 240 K, which is proposed to be a freezing transition of the mobility of sodium atoms. A similar behavior was observed in as-prepared γ-Na_0.66CoO₂ sample. However, another internal friction peak appears around 160 K. This internal friction peak is expected to be a thermally activated relaxation peak with some relationship to oxygen vacancies.