Effect of severe plastic deformation and thermomechanical treatment on the structure and properties of titanium

The effect of different modes of combined treatment on the microstructure and mechanical properties of long-length semiproducts from commercial purity titanium is studied. The combined production process includes equal-channel angular pressing followed by thermomechanical treatment. Special features of formation of an ultrafine-grain structure in preforms and changes in mechanical properties are studied in different stages of the process. A comparative analysis of mechanical characteristics of titanium in the initial annealed state and after the combined treatment is performed. Scattering of mechanical properties over the length of preforms is studied.     

强变形工艺对2519A铝合金组织与性能的影响

通过硬度测试、拉伸性能测试、透射电镜观察等分析手段研究了不同强变形工艺下2519A铝合金的力学性能与微观组织。结果表明,经50%的冷轧变形和165 ℃人工时效后,2519A合金的力学性能明显提高,其抗拉强度、屈服强度和伸长率分别为522 MPa、468 MPa和8.5%。而在冷变形前添加165 ℃×2 h预时效处理,合金的力学性能进一步提高,其抗拉强度、屈服强度和伸长率分别达到535 MPa、497 MPa和8%。预时效处理可以提高合金中θ′相的密度,使析出相分布更加均匀,有助于提高合金的力学性能。     

Effect of severe plastic deformation on the properties of the Fe-36% Ni invar alloy

Temperature dependences of the magnetization and thermal expansion coefficient of the Fe-36% Ni invar alloy in different structural states obtained upon plastic deformation by torsion under a quasihydrostatic pressure followed by annealing at different temperatures are studied. A decrease in the thermal expansion coefficient of the invar in a temperature range of 20–100°C and the formation of ordered precipitates (with a superstructure) were found to result from severe plastic deformation.     

Effect of severe plastic deformation on microstructure and mechanical properties of bulk AZ31 magnesium alloy

The equal channel angular pressing (ECAP) was used to make large plastic deformation of magnesium alloy, and ECAP processing and relevant process parameters were obtained by using finite element method. The strain distributions in the workpieces and the loads on the dies were studied. The mathematical model of accumulated deformation results, microstructure refinement and mechanical properties were established. Through the analysis, the relationships between grain refinement and mechanical properties were obtained. The refined grain size and the obtained mechanical properties are forecasted by using characterization of accumulation deformation.     

Effect of plastic deformation on the mechanical properties and structure of alloy Mg-3.6% Sm

Alloys based on magnesium which exhibit low density and specific strength are used as light structural materials. Alloying of magnesium alloys with REM promotes an increase in their strength properties both at room and elevated temperatures. The possibility is studied of an additional increase in strength properties on alloying magnesium with samarium as a result of plastic deformation.A. A. Baikov Institute of Metallurgy, Moscow. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 24–26, January, 1994.     

剧烈塑性变形对AZ31镁合金显微组织和力学性能的影响(英文)

通过等通道转角挤压技术(ECAP)对镁合金进行剧烈塑性变形,使用有限元法实现对ECAP加工过程及相关工艺参数的数值模拟,分析成形过程中的网格的变化、应力应变分布规律及其加载载荷规律,确定主要工艺参数影响规律。通过分析,得出晶粒细化程度与力学性能的关系,为镁合金的晶粒细化方法提供更合理的理论指导和参考依据。     

Effect of low-rate isothermal plastic deformation on the structure and properties of ZhS6KP nickel alloy

ZhS6KP alloy is used in commercial production of blades of aircraft engines pressed in Widin presses. Standard heat treatment that consists in air hardening from 1220°C (4 h) and aging at 950°C for 2 h with cooling in air does not always provide an optimum combination of long-term strength and fatigue resistance for the alloy at 900°C. In this connection, the possibility of improving the fatigue resistance and the long-term strength while preserving the high level of short-term mechanical properties by conducting low-rate plastic deformation before the heat treatment is considered.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 31 – 33, July, 1996.     

强变形Al-Cu合金的退火组织与性能

研究时效Al-Cu合金强塑性变形后退火过程中的显微组织与性能的变化.制备分别只含θ″、θ′和θ相的时效Al-Cu合金,在室温多向压缩变形(MAC)后进行低温退火,测试合金的拉伸性能,借助X射线衍射仪和透射电镜分析显微结构的变化.结果表明,合金中含θ″相和含θ′相试样分别在MAC变形8道次和12道次时,析出相完全回溶于基体,形成过饱和固溶体.在退火过程中,基体发生回复,并伴随粒子再次析出,产生析出强化,再析出速度比同温度下的常规时效快.在120 ℃退火时,析出相完全回溶的含θ″相试样和含θ′相试样的强度分别在前60和30 min上升,而析出相未回溶的含θ相试样的强度则下降;在150 ℃退火时,析出相完全回溶的含θ″相试样和含θ′相试样强度与退火前强度基本持平,而析出相未回溶的含θ相试样强度明显下降;在200 ℃退火时,析出相回溶的试样和未回溶的试样强度都出现明显下降.说明强变形Al-Cu合金退火时强度取决于析出强化与回复软化的综合作用.在所有试样中,MAC变形8道次的含θ″相试样在120 ℃下退火60 min,表现出最好的综合性能.     

Effect of rolling-assisted deformation on the formation of an ultrafine-grained structure in a two-phase titanium alloy subjected to severe plastic deformation

The effect of rolling in the temperature range 450–650°C on the fragmentation of the primary phase in a hot-rolled VT6 alloy rod preliminarily subjected to severe plastic deformation by equal-channel angular pressing at 700°C (scheme B _c, the angle between the channels is 135°, 12 passes) is studied. Rolling at 450°C without preliminary ECAP is shown not to cause α-phase fragmentation and to favor intense cold working of the alloy due to multiple slip. ECAP provides partial fragmentation of the initial structure of the α phase and changes the morphology of the retained β phase: it transforms from a continuous matrix phase into separated precipitates located between α particles. This transformation activates the fragmentation of the α phase during rolling at 550°C owing to the development of twinning and polygonization processes apart from multiple slip. Both a decrease (to 450°C) and an increase (to 625–650°C) in the rolling temperature as compared to 550°C lead to the formation of a less homogeneous and fragmented structure because of weakly developed recovery and intense cold working in the former case and because of the beginning of recrystallization and the suppression of twinning in the latter case. A relation between the structure that forms upon SPD followed by rolling and the set of its properties is found. A general scheme is proposed for the structural transformations that occur during ECAP followed by rolling at various temperatures.     

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 plastic deformation on the structure and properties of laminated composite materials

Experience with the development and application of plasma cutting of metals using reversed polarity current and mixed gas supply is described. The high efficiency of plasma cutting with reversed polarity in both the manual and automatic cutting modes in the plant conditions is stressed. It is noted that the number of activations of the constricted arc can be greater than 1000 without failure of the electrode.     

大塑性变形6013铝合金的时效特性与力学性能

利用X射线衍射分析（XRD）、差示扫描量热法（DSC）和拉伸试验,研究不同温度等通道转角挤压（ECAP）和常规静态时效处理后6013 Al-Mg-Si铝合金的微观结构、时效行为、析出动力学以及力学性能。XRD测得的ECAP变形后合金的平均晶粒尺寸在66-112 nm范围内,平均位错密度在1.20×10^14-1.70×10^14 m^-2范围内。DSC分析表明,由于ECAP后试样比常规时效处理试样拥有更细小的晶粒和更高的位错密度,因此,ECAP变形后合金的析出动力学更快。与未变形合金相比,ECAP后试样的屈服强度和抗拉强度都得到了显著提高。室温ECAP后试样的强度达到最大,其屈服强度是静态峰时效屈服强度的1.6倍。细晶强化、位错强化以及由于ECAP过程中的动态析出而产生的析出相强化,是ECAP合金获得高强度的几种主要强化机制。     

Effect of plastic deformation on the properties of VAD15 forging aluminium alloy and welded joints in this alloy

The results are presented of the investigations of the effect of the surfacing parameters on the penetration area and thermal efficiency in the conditions of constant heat input in automatic deposition of a bead on a thick component. The correction coefficients for calculating the penetration area using the well-known and corrected Rykalin equation for a constantly acting and rapidly moving point heat source on the surface of the thick component are determined.     

Effect of preliminary plastic deformation on the structure and physicomechanical properties of aging invar alloy N30K10T3

The invar alloy N30K10T3 after water quenching from 1150°C (austenite, γ phase) has the temperature of the start of martensitic transformation M _s ≈ ?80°C and the Curie temperature T _C ≈ 200°C. The effect of aging-induced phase decomposition in a deformed supersaturated solid solution on its hardness HV, electrical conductivity σ, magnetic permeability μ, and linear expansion coefficient β has been studied. It has been shown that cold plastic deformation of the alloy (at 20°C) to 30–50% increases its hardness, virtually does not change the conductivity, and decreases permeability. Aging of the deformed invar results in increasing HV and σ and decreasing μ. At room temperature, the deformed invar has a low linear expansion coefficient; its magnitude grows the faster, the greater the aging temperature T _a. Plastic deformation increases the density of dislocations, which form a banded substructure in austenitic grains. Besides, a metastable martensitic phase has been observed, which undergoes a reverse martensitic transformation into austenite upon heating in the temperature range from 550°C to 650°C. This transformation causes a decrease in the linear expansion coefficient β(T) of the deformed material. In samples aged at T _a = 700°C (after deformation), an athermal aging-induced martensite (α_a phase) appears after cooling them to 20°C. The appearance of the α_a phase is due to an increase in the temperature of the start of the martensitic transformation to above the room temperature caused by aging. In the samples containing the α_a phase, there is observed a decrease in β in the temperature range from 350 to 670°C, which is due to the reverse transformation of the aging-induced martensite into austenite (α_a → γ).     

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.     

Effect of severe plastic deformation on the microstructure and tribological properties of a babbit B83

The effect of severe plastic deformation carried out at room temperature by the methods of equal-channel angular (ECA) pressing and surface friction treatment (SFT) on the microstructure, rate of wear, and friction coefficient of a babbit B83 (11.5% Sb, 5.5% Cu, Sn for balance) has been investigated. It has been shown that severe plastic deformation that leads to a drop in the grain size of the babbit to 100–300 nm and to a strong refinement of particles of intermetallic phases (SnSb, Cu₃Sn) causes a considerable (twofold-fourfold) reduction in the rate of wear and a decrease in the friction coefficient of a steel-babbit pair under test conditions with lubrication at small (0.07 m/s) and enhanced (4.5 m/s) sliding velocities. As was shown by structural investigations performed with the use of scanning electron microscopy, this positive influence of severe plastic deformation on the tribological properties of the babbit is connected with the formation on the deformed-babbit surface of a developed porosity, which improves conditions for lubrication of the babbit-steel friction pair due to the action of the self-lubrication effect and thereby favors the retention of a stable regime of boundary friction of this pair. The formation of porosity is a result of the accelerated spalling of hard brittle intermetallic particles of SnSb and Cu₃Sn from the friction surface of the deformed babbit, which is caused by weakening and loss of the bonding of these particles with the plastic matrix (α solid solution based on tin) in the course of severe plastic deformation of the babbit. At the same time, under the conditions of dry sliding friction of the babbit-steel 45 pair, when a fatigue mechanism of wear of the alloy under consideration predominantly develops, this plastic deformation yields an approximately 1.6-fold increase in the rate of wear of the babbit. This increase is mainly due to numerous defects (microcracks) that are introduced into the babbit structure upon its severe plastic deformation and reduce the resistance of the surface layer of this material to the fatigue mechanism of wear.