贝氏体灰铸铁的内耗特征

本文论述了贝氏体灰铸铁在不同的振幅和频率测量条件下的内耗，并分别与相同碳当量的普通灰铸铁进行了比较。研究结果表明：贝氏体灰铸铁的内耗值是普通灰铸铁低频测量条件的1．5倍，高频测量条件的1．3—3倍，且内耗值随振幅增大而增大。     

D型石墨铸铁在600—700℃时抗氧化性的研究

试验了合金元素钛以及铸型冷却条件对灰铸铁抗氧化性的影响,研究了石墨大小和D型石墨的含量对灰铸铁抗氧化性的影响。试验结果表明:石墨越细小,灰铸铁的抗氧化性越好; D型石墨铸铁的抗氧化性优于A型石墨铸铁。     

A型和D型石墨合金灰铸铁断口形貌对比研究

介绍了D型石墨的合金灰铸铁在国内外的应用情况,以及试验生产A型和D型石墨Cr-Ni-Cu合金灰铸铁的方法,检查结果:A型石墨合金灰铸铁中的石墨较粗大;另外,在化学成分相近的情况下,D型石墨合金灰铸铁具有更高的抗拉强度。分析认为两种合金灰铸铁的断口主要是由于片状石墨解理以及石墨/基体之间的界面分离造成的,其中D型石墨合金灰铸铁断口表面的显微疏松更少,枝晶更发达,这正是其具有更高强度、适于制造液压元件的原因。     

流变法铸造石墨铝挤压铸造工艺参数的正交试验研究

本文采用正交试验法研究了用流变法制造石墨铝复合材料的挤压铸造工艺参数,分析讨论了几种工艺参数对石墨铝内耗值的影响。     

灰铸铁弹性模量的影响因素

研究了温度、石墨形态、基体组织,合金元素等因素对灰铸铁弹性模量的影响,结果表明:灰铸铁的弹性模量E_0随温度变化,在某一温度出现峰值;E_0主要与石墨有关,而基体对其影响不大;b值与石墨、基体部有关系.     

珠光体基体灰铸铁内耗、共振频率及组织的关系研究

采用自由衰减法在常温和变温下测试了不同条件下所得铸铁阶梯试样的内耗值,并对所测位置的石墨分布状态进行量化统计,进而研究铸铁内耗的影响因素。分析结果表明,石墨的面积及周长对铸铁内耗有着重要影响,且铸件的共振频率始终与内耗有着相反的变化规率;在升温测试条件下,铸铁内耗试样会在100℃左右出现内耗峰。     

铅对灰铸铁组织和性能的影响

生产过程中炉料所含过量的铅会对灰铸铁件性能产生重要影响.因此研究了铅的不同添加量对灰铸铁力学性能和组织的影响,并进行了复制魏氏石墨及不同孕育剂的试验.结果表明:铅会使石墨变异,并在一定条件下,形成魏氏石墨,这明显降低了灰铸铁件的力学性能;采用锆硅孕育剂能够缓解铅对铸铁石墨形态的影响.     

钛对D型石墨铸铁组织和性能的影响

研究了钛对灰铸铁组织和性能的影响。试验表明,不同含量的钛对灰铸铁组织和性能产生不同的影响。在一定含量范围内,钛促进灰铸铁D型石墨的形成,改善灰铸铁石墨形态,并提高灰铸铁的强度性能。对钛对灰铸铁组织和性能作用的机理提出了看法。     

硫对灰铸铁组织和性能的影响

在电炉熔炼条件下,采取往铁液中加入FeS增硫的方法,研究和探讨了硫对灰铸铁组织和性能的影响.试验结果表明:硫从0.020%上升到0.061%,灰铸铁强度可提高50MPa以上,硬度值可提高20个HB,灰铸铁白口倾向减小,A型石墨增多,断面均匀性得到改善,进一步提高硫到0.101%时,上述指标值变化不大.此外,用电子探针对灰铸铁组织进行的微区分析发现,石墨内部有大量的Si、Ba、S和Mn等元素的富集,据此可以认为,上述元素的硫化物在灰铸铁凝固过程中起着石墨形核的基底作用.     

利用大量回炉料和废钢生产高牌号灰铸铁

介绍了铸铁冶金质量指标及其影响因素,分析了利用大量回炉料加废钢生产的灰铸铁力学性能、切削加工性能和铸造性能比普通灰铸铁优良的原因.生产实践表明,生产此类灰铸铁的要点是增碳、高温熔炼和控制ω(C)、ω(Si)量;此类灰铸铁的三角试块断口组织致密、呈银灰色、白口宽度不大,抗拉强度为290 MPa,石墨由90％的A型石墨和10％的B型石墨组成,基体组织为5％铁素体+95％珠光体.在焦炭质量及供风条件一定的情况下,温度越高,增碳率越高,废钢用量比例可以越大.     

等温时效过程Cu—Al—Be形状记忆合金内耗行为研究

对ＣｕＡｌＢｅ合金在等温时效过程中的内耗特性进行了研究。结果表明,等温时效时该合 金内耗主要是由应力诱发马氏体相变和Ｍ／Ｍ、Ｐ／Ｍ界面在交变应力下的粘滞性迁移所引起的。 时效过程中,合金内耗迅速下降,至一定值后趋于稳定,且大小受测量频率影响。在马氏 体态时效时,内耗衰减曲线出现峰值,这与试样中的淬火空位及其在时效时的界面扩散有 关。     

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.     

Investigation on microstructure and internal friction for low density TiB2/ZL114 composites

TiB₂/ZL114 composites with the density of 2.733 g/cm³ were fabricated through reaction of K₂TiF₄ and KBF₄ (LSM method). The composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The internal friction measurements were performed on DTM-II-J dynamic modulus damping analyzer and the mechanisms were investigated. Experimental results indicate that reinforced particles are well-distributed in the matrix and the internal friction value of TiB₂/ZL114 composites is up to a maximum of 9.04x10^-3, almost twice that of ZL114. The internal friction results form dislocation vibration within the material, the sliding of grain boundary and phase interface, and together with the micro-plastic deformation caused by difference in coefficients of thermal expansion and elasticity modulus of various phases. The average internal friction values of samples with the sizes of 40 mmx4 mmx2 mm, 40 mmx8 mmx2 mm and 40~mm$\times 25 mmx2 mm are 8.83x10^-3, 8.89x10^-3, and 8.93x10^-3, respectively. Thus, the developed composites are of low density, high internal friction, and the sizes of samples have no relation to the internal friction behavior.     

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 and loss tangent of nonlinear viscoelastic materials: different concepts, different results

This paper aims to give some insight into measurements of the nonlinear processes involved in the dynamical response of viscoelastic materials. The main goal is to point out that these nonlinear effects can be observed with forced oscillating torsion pendulums, but by measuring the complete hysteretic loop, instead of just looking at the phase lag angle. The response of a nonlinear rheological model constructed with a standard anelastic element in series with a nonlinear dashpot is considered. The characteristic parameters of this model are according to previous empirical results reported in the literature. This system is dynamically driven as if it were in a forced torsion pendulum, which is almost the optimal device for the analysis of amplitude dependent internal friction at low frequencies. The intrinsic internal friction is calculated from the ratio between the dissipated energy per cycle and the maximum stored energy for the nonlinear rheological model. The simulation of the internal friction that could be measured with a torsion pendulum for the rheological model is then determined from the intrinsic internal friction after considering the non-homogeneous strain distribution. The intrinsic internal friction and the simulated internal friction data are compared with the tangent of the phase angle by which the strain lags behind the stress in order to show that the differences are important enough to be measured. In summary, the nonlinear response could potentially be measured with commercial equipment, but usually is not, because only the phase lag angle is considered. Automatic measurements of both the temporal evolution of stress and strain in a cycle will lead to the determination of the real value of the internal friction of nonlinear systems from the hysteretic σ– loop.     

PREBAINITIC TRANSFORMATION IN A Cu-Zn-Al ALLOY

使用微机自动控制相变内耗仪,以0.7Hz频率测量Cu-25.83wt-％Zn-3.96wt-％Al合金在贝氏体相变温区等温过程中的内耗和频率随时间的变化,实验结果显示,在孕育期内随时间出现内耗峰值Q_(max)~(-1)且Q_(max)~(-1)随等温温度升高(孕育期缩短)而升高,达到Q_(max)~(-1)所需时间却随等温温度升高而缩短.在等温初期频率最低,随时间延长逐渐上升至稳定值.在施加8×10~5Pa拉应力的条件下,重复上述等温测量表明,Q_(max)~(-1)升高,达到Q_(max)~(-1)所需的时间缩短,且初期频率下降更为显著. 本文揭示:Cu-Zn-Al合金贝氏体相变存在类似于热弹性马氏体相变的点阵软化现象。在贝氏体相变孕育期内存在预相变的主要过程为形核。等温内耗的变化规律可根据相变理论和局部软化理论,通过孕育期内形核率J~*的变化作出解释。     

Effect of ageing on transformation kinetics and internal friction of Ni-rich Ni–Ti alloys

In Ni-rich Ni–Ti alloys the ageing treatments create finely dispersed Ti₃Ni₄ precipitates in the B2-based matrix. Formed precipitates are known to influence the phase transformation temperatures and to facilitate the R-phase transformation. In addition to the change in the phase transformation behaviour, the ageing treatments are also reported to affect internal friction and mechanical properties of Ni–Ti alloys.In the present work, by means of systematic DSC and DMA studies the effects of the ageing treatments on the phase transformation as well as on the internal friction and mechanical properties of Ni-rich Ni–Ti alloy were studied. As an extension to earlier studies, the present study concentrates both on the effects of the ageing time and the ageing temperature systematically. By combining the results of the DSC measurements of phase transformation behaviour to the DMA measurements of internal friction and mechanical behaviour of the Ni-rich Ni–Ti alloy, the present study gives yet unpublished information about the comprehensive effects of the ageing treatments on these alloys. These results enable to control the phase transformation temperatures, internal friction and mechanical properties of the Ni-rich Ni–Ti alloy by selecting the suitable ageing treatment.Results showed that the noticed effects of the ageing treatments on mechanical properties could be explained with the changes in the size, distribution, density and coherency of the formed Ti₃Ni₄ precipitates. The high internal friction values can be explained as the contribution of the internal stress fields and increased amount of mobile interfaces as the result of the formed Ti₃Ni₄ precipitates. The amount of mobile interfaces seems to be more dominant factor for the increased internal friction value than the effect of the internal stress fields. Therefore, the optimal internal friction values can be obtained with a proper aging treatment which will yield a high density of small Ti₃Ni₄ precipitates.     

CuZnAl合金的马氏体及其相变的阻尼性能SCIEI

本文研究了CuZnAl合金在马氏体及马氏体相变时的阻尼性能。结果表明,在马氏体状态的内耗是一种M/M界面内耗,利用位错内耗理论的表达式可解释其变化规律。在马氏体相变区的内耗,包括M/M界面内耗及相变内耗两级分,其中相变内耗又由马氏体逆转变产生的内耗及应力诱发马氏体内耗两部分组成,并且前者占主导地位、合金阻尼性能的衰减与激振过程中引入的位错有关,并在一定振动次数后趋向一稳定值。     

基于轮廓法测试镍基高温合金惯性摩擦焊接头内部残余应力

采用轮廓法(contour method)测试小直径FGH96镍基高温合金惯性摩擦焊接接头的内部环向应力。详细介绍了轮廓法测试步骤,包括试样切割、切割面轮廓测试、数据处理和有限元分析;获得了FGH96镍基高温合金惯性摩擦焊接接头内部环向应力分布全貌并分析其分布特征。测试结果表明:镍基高温合金惯性摩擦焊接接头的焊缝中心位置环向应力为非常大的拉应力,峰值拉应力为1200 MPa,达到材料室温时的屈服强度;焊缝区域(距焊缝中心±5 mm区域)近内壁区域的环向应力大于外壁区域环向应力,垂直焊缝方向的环向应力变化梯度非常大;远离焊缝区域,焊缝两侧的环向应力不对称。