Superelasticity and Shape Memory Effect Under Tension and Compression in the [001]-Oriented Single Crystals of Non-Equiatomic FeNiCoAlTi High-Entropy Alloy

Russian Physics Journal - The effect of γ′-phase dispersed particles on the temperature dependence of the stresses of the start of martensitic transformations σcr(T), the shape...     

Superelasticity and the propagation of shock waves in crystals

The separation of a shock wave into an elastic precursor and a plastic wave is a characteristic phenomenon occurring only in solid media. The existence of the elastic shock wave at pressures p ≈ 10 GPa, which is one or two orders of magnitude higher than the dynamic elastic limit, has been detected in recent numerical calculations and a femtosecond laser experiment. The plastic shock wave has no time to be formed in these ultrashort waves at p ≈ 10 GPa. The processes of the formation and propagation of the elastic and plastic waves in aluminum at higher pressures obtained by means of femtosecond lasers have been analyzed in this work. It has been found that the elastic precursor survives even under the conditions when the pressure behind the plastic front reaches a giant value p ∼ 1 Mbar at which the melting of the metal begins. It has been shown that superelasticity should be taken into account to correctly interpret the preceding laser experiments.     

Quenched noise in surface growth

The analytical continuous equations for the Tang and Leschhorn (Phys. Rev. A 45 (1992) R8309) and the Buldyrev et al. (Phys. Rev. A 45 (1992) R8313) models are derived from the microscopic rules using a regularization procedure. As was shown in a previous paper (Phys. Rev. E 62 (2000) 6970) the continuous equation for the Tang and Leschhorn model is formally different to the Kardar–Parisi–Zhang equation (Phys. Rev. Lett. 56 (1986) 889) with quenched noise (QKPZ). Nevertheless, after expanding the multiplicative noise, it is shown that we recover the usual QKPZ, demonstrating analytically that both equations belong to the same universality class.     

Peculiar Features of Thermal Aging and Degradation of Rapidly Quenched Stainless Steels under High-Temperature Exposures

This article presents the results of comparative studies of mechanical properties and microstructure of nuclear fuel tubes and semifinished stainless steel items fabricated by consolidation of rapidly quenched powders and by conventional technology after high-temperature exposures at 600 and 700°C. Tensile tests of nuclear fuel tube ring specimens of stainless austenitic steel of grade AISI 316 and ferritic–martensitic steel are performed at room temperature. The microstructure and distribution of carbon and boron are analyzed by metallography and autoradiography in nuclear fuel tubes and semifinished items. Rapidly quenched powders of the considered steels are obtained by the plasma rotating electrode process. Positive influence of consolidation of rapidly quenched powders on mechanical properties after high-temperature aging is confirmed. The correlation between homogeneous distribution of carbon and boron and mechanical properties of the considered steel is determined. The effects of thermal aging and degradation of the considered steels are determined at 600°C and 700°C, respectively.     

40GPa压力范围内铜和铝的准等熵压缩线

 基于自行研制的磁驱动准等熵压缩加载实验装置CQ-1.5,利用全光纤位移干涉仪（Doppler Pins System, DPS）、激光速度干涉计（Velocity Interferometer System for Any Reflectors, VISAR）两种测试手段,以及反积分数据处理方法,实验测量了40 GPa压力范围内T1铜、LY12硬铝和L1纯铝3种材料的准等熵压缩线,将实验准等熵压缩线与基于Grüneisen状态方程的理论等熵压缩线和冲击Hugoniot线进行了比较。结果表明,在该压力范围内,实验准等熵压缩线与理论等熵压缩线相一致,两者偏差小于3%;实验准等熵压缩线靠近冲击Hugoniot线,位于其下方,与国外文献发表的结果相同,进一步表明,实验测量结果正确可靠。     

快速压缩作用下橄榄石的结构稳定性

结合不同的温度效应,研究了快速压缩过程对橄榄石结构稳定性的影响。分别在293、373、473、573、673、773 K下将橄榄石快速加压至3 GPa,在873、973、1073、1173 K下烧结橄榄石样品2 h后再在室温下快速加压至3 GPa。采用同步辐射X射线衍射、拉曼光谱、红外吸收光谱以及扫描电镜等技术分析了回收样品的结构和微观形貌。结果表明,上述过程中橄榄石结构均稳定,未发生由压力和温度导致的相变。橄榄石回收样品的微观形貌发生变化,晶粒细化。由于回收样品中存在残余应力以及晶粒细化,橄榄石的822 cm^–1和854 cm^–1拉曼特征峰出现了展宽和偏移。     

Spalling in Sapphire in Different Crystallographic Directions under Shock Compression

Technical Physics - The tensile strength of single-crystal sapphire specimens with c, a, d, r, n, s, g, and m crystallographic orientations (c-, a-, d-, r-, n-, s-, g-, and m-axis specimens) has...     

Pulse Compression and Tension of Epoxy Resin under Shock-Wave Action

Technical Physics - The shock-wave properties of ED-10 epoxy resin have been studied using VISAR and PDV multiple-channel laser interferometers. The Hugoniot of epoxy resin and pressure dependence...     

钽铌合金材料的冲击压缩特性研究

 对一种新型的钽铌合金材料进行了冲击压缩特性实验研究，通过超声测量得到了其常态下的横波和纵波声速，进而计算得到了其相关的一些静态力学参量。通过二级轻气炮加载技术，得到其在60~196 GPa压力范围内的冲击Hugoniot线。这一测量结果与混合物叠加法估算的结果符合较好，并将这种新型合金材料的力学特性与两种钨合金材料进行了简单对比。比较结果显示，Ta-Nb合金材料是一种具有较好工程应用前景的材料。     

冲击压缩下金属的电导率测量

 探索了一种在兆巴压力冲击压缩下测量金属电导率的新方法——四电极垂向引线法，并用刻槽单晶蓝宝石作绝缘腔体，以消除分流效应对测量结果的影响。用二级轻气炮作为加载手段，测量了铁在终态平衡压力为101～208 GPa压力区间内的电导率（电导率从1.45×10⁶ S/m变化到7.65×10⁵ S/m）。将测量铁电导率的压力范围扩展到了200 GPa以上。实验结果表明，关于金属电导率的Bloch-Grüneisen公式在高达200 GPa冲击压力下仍然有效（对于ε-铁）。     

Quenched and Annealed Critical Points in Polymer Pinning Models

We consider a polymer with configuration modeled by the path of a Markov chain, interacting with a potential u + V _n which the chain encounters when it visits a special state 0 at time n. The disorder (V _n ) is a fixed realization of an i.i.d. sequence. The polymer is pinned, i.e. the chain spends a positive fraction of its time at state 0, when u exceeds a critical value. We assume that for the Markov chain in the absence of the potential, the probability of an excursion from 0 of length n has the form \({n^{-c}\varphi(n)}\) with c ≥  1 and φ slowly varying. Comparing to the corresponding annealed system, in which the V _n are effectively replaced by a constant, it was shown in [1,4,13] that the quenched and annealed critical points differ at all temperatures for 3/2 < c < 2 and c > 2, but only at low temperatures for c < 3/2. For high temperatures and 3/2 < c < 2 we establish the exact order of the gap between critical points, as a function of temperature. For the borderline case c = 3/2 we show that the gap is positive provided \({\varphi(n) \to 0}\) as n → ∞, and for c > 3/2 with arbitrary temperature we provide an alternate proof of the result in [4] that the gap is positive, and extend it to c = 2.     

Random Walks and Polymers in the Presence of Quenched Disorder

After a general introduction to the field, we describe some recent results concerning disorder effects on both ‘random walk models’, where the random walk is a dynamical process generated by local transition rules, and on ‘polymer models’, where each random walk trajectory representing the configuration of a polymer chain is associated to a global Boltzmann weight. For random walk models, we explain, on the specific examples of the Sinai model and of the trap model, how disorder induces anomalous diffusion, aging behaviours and Golosov localization, and how these properties can be understood via a strong disorder renormalization approach. For polymer models, we discuss the critical properties of various delocalization transitions involving random polymers. We first summarize some recent progresses in the general theory of random critical points: thermodynamic observables are not self-averaging at criticality whenever disorder is relevant, and this lack of self-averaging is directly related to the probability distribution of pseudo-critical temperatures T _c(i,L) over the ensemble of samples (i) of size L. We describe the results of this analysis for the bidimensional wetting and for the Poland–Scheraga model of DNA denaturation.Conference Proceedings “Mathematics and Physics”, I.H.E.S., France, November 2005     

The Kaiser Effect under Multiaxial Nonproportional Compression of Sandstone

Doklady Physics - The regularities of deformation and fracture of sandstone under nonproportional biaxial and triaxial cyclic compression accompanied by the rotation of the Lamé ellipsoid and...     

Quenched disorder in a hierarchical Coulomb gas model

The effects of quenched disorder on the two-dimensional Coulomb gas are studied in the hierarchical approximation. The quenched random variables interact with the charges via a potential that decays as an inverse power () of the distance. Recursion relations for the single block charge activities are derived in which the quenched variables explicitly appear. In a linear approximation, for all1, with some restrictions on the variance of the normally distributed random variables, it is shown that the charge activities converge to the Kosterlitz-Thouless fixed point for all sufficiently low temperatures and sufficiently large blocks. The annealed system is also examined. This model is shown to have a Kosterlitz-Thouless phase only for an intermediate range of temperatures. At low temperatures the activities can diverge, and large charges can exist on all length scales.     

A Phase Transition in a Quenched Amorphous Ferromagnet

Quenched thermodynamic states of an amorphous ferromagnet are studied. The magnet is a countable collection of point particles chaotically distributed over \(\mathbb {R}^d\) , \(d\ge 2\) . Each particle bears a real-valued spin with symmetric a priori distribution; the spin-spin interaction is pair-wise and attractive. Two spins are supposed to interact if they are neighbors in the graph defined by a homogeneous Poisson point process. For this model, we prove that with probability one: (a) quenched thermodynamic states exist; (b) they are multiple if the intensity of the underlying point process and the inverse temperature are big enough; (c) there exist multiple quenched thermodynamic states which depend on the realizations of the underlying point process in a measurable way.     

Avalanche Dynamics in Quenched Random Directed Sandpile Models

We numerically investigate the quenched random directed sandpile models which are local, conservative and Abelian. A local flow balance between the outflow of grains during a single toppling at a site and the total number of grains flowing into the same site plays an important role when all the nearest-neighbouring sites of the above-mentioned site topple for once. The quenched model has the same critical exponents with the Abelian deterministic directed sandpile model when the local flow balance exists, otherwise the critical exponents of this quenched model and the annealed Abelian random directed sandpile model are the same. These results indicate that the presence or absence of this local flow balance determines the universality class of the Abelian directed sandpile model.     

Variation of the 13C Diamond Properties under Isothermal Compression

Technical Physics - The parameters of atomic interaction pair potential for 13C diamond have been determined from experimental data on the ratio of Raman frequencies for isotopically different...