Kinetics of atomic ordering of Cu-49 at % Pd alloy after severe plastic deformation

Resistometry has been employed to study kinetics of the disorder → order phase transformation in the Cu-49 at % Pd alloys in as-quenched and deformed (to various degrees of deformation) states. Diagrams of transformation kinetics upon isothermal annealing have been plotted and the activation energy of atomic ordering after severe plastic deformation has been estimated (? ≈ 7.1). The possibility of achieving a single-phase ordered state with an extremely low electrical resistivity in the alloy studied has been demonstrated.     

4GPa压力处理对Cu-11.68Al合金塑性变形的影响

采用纳米压痕法测量了4 GPa压力处理前后Cu-11.68Al合金的塑性变形量,并借助光学显微镜和透射电镜对其组织进行分析,探讨了4 GPa压力处理对Cu-11.68Al合金塑性变形的影响。结果表明,4 GPa压力处理能细化Cu-11.68Al合金组织,增大组织内部的位错密度,有效地减小Cu-11.68Al合金的塑性变形量,经2000 μN 载荷保持30 s后,4 GPa压力处理后Cu-11.68Al合金的塑性变形量为98.22 nm,较高压处理前减少了22.13%。     

Effect of heat treatment on the structural and phase transformations and mechanical properties of TiNi alloy subjected to severe plastic deformation by torsion

Effect of annealing on the structural and phase transformations and mechanical properties of large-size samples of the Ti_49.4Ni_50.6 alloy preliminary subjected to severe plastic deformation by torsion under a high pressure (HPT) is studied. The study was performed by transmission and scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and measurements of mechanical properties. The annealing was found to result in the nanocrystallization of initial samples amorphized by HPT. In this alloy, the high-strength uniform nanostructured state is formed the size of nanocrystalline grains of which and the mechanical properties depend on the temperature and time of annealing.     

应变能对Al-Cu合金强变形诱导析出相回溶的影响

透射电镜观察表明,Al-4.11%Cu二元合金中θ′相在等径角挤压(ECAP)强变形中发生反复的弯曲变形,形成了亚结构,并从亚结构界面处开始发生溶解,而θ相则发生了折断和破碎,并从破碎θ粒子的尖角处发生溶解。X射线衍射及小角度X射线散射测试结果表明,θ′相粒子随强变形溶解得比θ快,θ′相粒子在尺寸较大时即开始随强变形溶解。热力学分析表明,θ′相在强变形中因为自身的应变增加了系统的应变能和粒子回溶的驱动力,促使其在强变形中的溶解。而θ相的溶解则是因为破碎粒子尖锐菱角表面能的增加造成的。研究表明,析出相粒子应变能与表面能都是强变形诱导析出相粒子回溶的驱动力,尤其是应变能的作用更大。     

On the structural and phase transformations in solids induced by severe plastic deformation

Based on the analysis of our own and literature data, as well as on the principles of nonequilibrium thermodynamics, the influence of plastic deformation on the diffusion, structural, and phase transformations in solids at different temperatures is considered. The main regularities for all effects can be explained from a unified point of view based on the attainment of the critical internal energy in solids due to the high density of accumulated, interacting, and moving defects. This leads to various transformations at the expense of growth in the the phase energy to the extent that the thermodynamics of alloys and their phase diagrams change up to the transition of the alloys into to a state that, from the view-point of thermodynamics, corresponds to liquid. The high number density of moving defects facilitates the diffusion processes, which contributes to rapid transformations, even at liquid nitrogen temperatures.     

塑性变形对铝合金弹性模量的影响

回弹是影响弯曲件精度的主要障碍 ,而弹性模量是影响回弹的重要因素之一。一般工程应用中都把弹性模量作为常数 ,而实际上弹性模量随塑性变形的进展在不断发生变化。为了准确把握弹性模量值在塑性变形过程中的变化规律 ,针对应用广泛的铝合金材料 ,采用静力学实验方法 ,对常用的退火LY12及退火LF2 1铝合金的弹性模量在塑性变形中的变化情况进行了实验研究。得到了弹性模量值随塑性变形程度及加载方式变化的规律 ,并分别归纳为数学模型。     

Phase and structural transformations in the aluminum amts alloy upon severe plastic deformation using various techniques

The paper presents experimental data on the structure formation in the commercial aluminum alloy of grade AMts subjected to severe plastic deformation using dynamic channel-angular pressing and torsion under high quasi-hydrodynamic pressure in Bridgman anvils. The dependences of the structural characteristics and hardness on the degree, rate, and scheme of deformation have been analyzed.     

Effect of the rate of cold plastic deformation on the kinetics of mechanical alloying of the Fe-35Ni-5Al alloy

The strain-induced dissolution of Ni₃Al intermetallic particles in the matrix of the aging Fe-35Ni-5Al alloy has been found to become more intense with increasing rate of deformation in rotating Bridgman anvils. This regularity has been presumably explained by a disbalance in the kinetics of the dual process of strain-induced dissolution and formation of phases owing to an increase in the number of interstitial atoms and a retardation of the development of an alternative process of the precipitation of second phases with increasing rate of deformation.     

Microstructure of an ordered Cu-40 at % Pd alloy

An electron-microscopic analysis of the microstructure of a Cu-40 at % Pd alloy ordered by B2 type has been carried out. The observed structural states have been shown to depend on the initial state of the alloy and ordering conditions. Previously unknown peculiarities of the fine structure of the ordered phase have been revealed, and assumptions about the nature of the observed phenomena have been made.     

Structural and phase transformations in a titanium alloy of the transition class under the effect of deformation

Structural and phase transformations in the VT22 (α + β) titanium alloy of the transitional class that occur during cold plastic deformation (CPD) by upsetting under the conditions of limited friction have been studied and the evaluation of the nonuniformity of deformation along the height of the deformed samples has been performed. It has been found that a CPD of the alloy quenched from the β field with degrees of reduction higher than 6% results in the formation of a martensite-like τ phase (bct) with an axial ratio c/a less than 1; upon upsetting with reductions exceeding 16%, α″ martensite appears in the structure. It is shown that the structural transformations in the alloy with the above degrees of deformation are realized in the following sequence: easy slip (ɛ = 1.5%); multiple slip (ɛ = 6%); the formation of a cellular structure (ɛ = 16%); the formation of deformation twins (ɛ = 23% and higher). The morphology of phases and structural constituents at all stages of the alloy treatment has been established and the distribution of the degree of deformation over the height of the deformed samples has been calculated.     

变形率和热处理制度对Nb47Ti合金显微组织的影响

通过对比Nb47Ti合金在4种变形率和4种热处理制度下的显微组织.结果发现:晶粒的生长受到热加工变形率、热处理温度等综合因素的影响,变形率对再结晶温度影响较大;当变形率达到80%以上时,再结晶可以在较低的温度下进行,选择合适的热处理制度,能够获得具有细小和均匀显微组织的Nb47Ti合金.