Effect of severe plastic deformation on the structure,microhardness, and wear resistance of the surface layer of titanium subjected to gas nitriding

The effect of severe plastic deformation under dry sliding friction on the structure, microhardness, and wear rate of the VT1-0 titanium subjected to gas nitriding has been studied. It has been shown that this deformation leads to the formation of a nanocrystalline structure with an α-crystal size of 10–100 nm and a microhardness of ～3.1 GPa in a surface layer up to 10 μm thick. The presence of this structure intensifies the saturation of the surface of the titanium with nitrogen in the course of subsequent gas nitriding at temperatures of 650–750°C. The formation of the nitride nanocrystalline TiN phase in the deformed titanium occurs at a relatively low nitriding temperature (700°C) and a short-term holding (2 h). The volume fraction of the nitride phase, which is formed in the layer up to 10 μm thick, reaches a few tens of percent, which leads to an increase in the microhardness of the nitrided surface of the titanium deformed by friction. Preliminary severe plastic deformation has a negative effect on the fatigue wear resistance of the nitrided titanium due to an increased brittleness of the deformed and subsequently nitrided surface layer of this material.     

Utilizing the resistance to microplastic deformation during aging of beryllium

Conclusions Commercial and distilled beryllium has the highest resistance to microplastic deformation after aging at 500 and 400°C, respectively. The aging of beryllium depends on the presence of iron in it.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 54–55, March, 1972.     

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.     

Improving the wear resistance of titanium-bronze friction couples by plastic deformation

Conclusion To improve the antifriction properties and the fatigue strength of friction couples of titanium and AMts9-2 bronze we recommend the use of roller or ball burnishing as the final operation.Translated from Metallovedonie i Termicheskaya Obrabotka Metallov, No. 1, pp. 77–78, January, 1974.     

时效处理对金属铍剩余电阻比的影响

运用电位方法测量纯金属铍剩余电阻比,研究了时效处理制度对金属铍的剩余电阻比的影响。结果表明：金属铍的剩余电阻比不仅与时效温度和金属内杂质的浓度有关,而且受时效时间的影响;剩余电阻比值随金属铍样品纯度的增加而增加,纯金属铍（纯度大于99.91%）的剩余电阻比值为20-147,并随时效温度和时效持续时间的不同而变化;高纯度（99.94%）金属铍具有合金时效处理倾向,可以作为时效型微合金来研究杂质对金属的性能影响。     

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.     

真空时效对QBe2铍青铜组织与性能的影响

用金相显微镜和拉伸试验机研究了真空时效对QBe2铍青铜的力学性能和微观组织的影响.结果表明,时效初期,材料强度提高、伸长率下降;峰时效后,随着温度和时间延长,强度趋向稳定,但伸长率不断下降;时效后晶内析出弥散分布的细小析出相,晶界出现不连续的析出相;双级时效可提高材料强度,但降低伸长率.QBe2铍青铜的最佳真空时效工艺为320℃保温2h,随炉冷却.     

新型Cu-Al-Fe-Ni变形铝青铜的固溶和时效强化

采用正交试验法,结合金相、X射线衍射、扫描电镜、能谱和力学性能等分析测试手段,对一种自主研发的Cu-Al-Fe-Ni变形铝青铜的固溶和时效强化工艺进行研究。结果表明:固溶时效工艺参数对合金抗拉强度、伸长率和硬度的作用主次顺序为时效温度、固溶温度、时效时间、固溶时间,其中温度对合金力学性的影响趋势单一,但时间的影响较复杂。经优化获得的最佳固溶时效工艺为:先在880℃下固溶3 h、水淬,再在480℃下时效1 h、空冷。合金的抗拉强度达810 MPa,伸长率达9%,硬度达255 HB,其综合力学性能比挤压态合金的有较大幅度的提高;软硬相的面积比及其显微硬度对合金的力学性能有较大的影响。     

Effect of severe plastic deformation on the formation of the nanocrystalline structure and the aging of the multicomponent aluminum-lithium alloy with small additions of Sc and Mg

Effect of severe plastic deformation and subsequent low-temperature annealing on the structural and phase transformations, which are realized in the alloy 1450 on the base of the Al-Li-Cu-Zr system with additives of Sc and Mg has been studied by electron microscopy. The possibility of obtaining a nanocrystalline recrystallized structure in the alloy investigated has been established. It has been shown that its uniformity and dispersiveness depend on the degree of deformation and on the regime of annealing and are determined by the density distribution of particles that are precipitated upon the decomposition of the supersaturated solid solution. The transition of the alloy from microcrystalline to submicrocrystalline or nanocrystalline state changes its phase composition, morphology, and mechanism of nucleation of the precipitated phases and makes it possible to minimize structural factors that exert negative effect on the alloy plasticity.     

Effect of various kinds of severe plastic deformation on the structure and electromechanical properties of precipitation-strengthened CuCrZr alloy

The effect of various kinds of severe plastic deformation (equal-channel angular pressing and quasi-hydrostatic extrusion at 77 and 300 K) on the structural formation of precipitation-strengthened CuCrZr alloy has been studied. A combination of experimental methods has been used. Sputtering by deuterium ions was used as the tool for the layer-by-layer study of the alloy structure. The difference between the sputtering yields of the matrix (copper) and precipitates (Cr and Zr) allowed us to visualize the alloy structure to a total depth of 0.5?1 μm. The effect of severe plastic deformation on the precipitate distribution is considered. It has been shown that the main peculiarity of the microstructure is related to the high density of precipitates enriched in chromium, which completely determine the surface roughness. Their distribution is not related to the grain size. The combination of equal-channel angular pressing and quasi-hydrostatic extrusion was shown to lead to the increase in the microhardness of the CuCrZr alloy to 2300 MPa in the case of low-temperature quasi-hydrostatic extrusion (at 77 K) and to the retained high conductivity. It has been proved that the high anisotropy of precipitate shape, microhardness, and sputtering yield of the CuCrZr alloy is determined by equal-channel angular pressing.     

Structure and microhardness of chromium-zirconium bronze subjected to severe plastic deformation by dynamic channel-angular pressing and rolling

Bulk samples of chromium-zirconium bronze have been subjected to severe plastic deformation by two methods, namely, high-strain-rate dynamic channel-angular pressing (DCAP) and quasistatic deformation by rolling. After deformation and additional aging using metallography and electron microscopy, the structure has been investigated and the microhardness of the samples has been measured. It has been shown that the high-strain-rate deformation by DCAP is of a periodic character. It has been established that, in the investigated bronze subjected to DCAP, in four passes, the structure of dynamic polygonization is predominantly formed, which is accompanied by processes of aging. Upon the rolling, cells of deformation origin and a structure with randomly distributed dislocations and numerous extinction contours are formed.     

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.     

Effect of silicon on the structure and wear resistance of high-carbon, chromium-manganese alloys

Conclusions  

The influence of deformation heat treatment on the structure and wear resistance of cuznpb brass

The influence of different deformation heat treatments on structure and wear resistance under dry sliding was studied under sliding velocity of 0.79 m/c, pressure of 0.2 to 1.0 N/mm2, and sliding distance of 1500 m. It was established that the deformation heat treatment led to the creation of a microcrystalline structure (2 to 3 μm) by recrystallization in the alloy. The wear rate of the alloy with the microcrystalline structure was 1.5 to 2.0 times less and 25 to 30 % less than in the β- phase state and the initial state, respectively.     

Effect of hardening and aging on thl resistance of nitrided niobium and its MN-1 alloy to low plastic deformation

Niobium, which possesses a unique combination of a high melting temperature (2465°C) and a low modulus of normal elasticity (80,000 –100,000 N/mm²), is a promising base for the creation of heat-resistant spring materials. In addition to the traditional technology, an efficient method for strengthening niobium and its alloys is gas nitriding, especially when it is combined with other strengthening techniques. The limited and temperature-dependent solubility of nirogen in niobium predetermines possibilities of using nitriding and subsequent heat treatment (hardening and aging) for improving the strength characteristics of thin-sheet materials. It is difficult to alloy refractory metals by metallurgical methods due to the high thermodynamic stability of nitrides and the desorption of nitrogen in vacuum. A more available and reliable method for bulk nitrogen alloying is suggested that consists in nitriding semiproducts of small cross section (complete penetration saturation). The present work is devoted to an investigation of the resistance of nitrided niobium and its MN-1 allov to low plastic deformations at room and elevated temperatures after hardening and aging.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 33 – 36, July, 1996.