On the effect of plastic deformation on the coarsening of ϑ-phase precipitation in an Al-Cu alloy

In the present investigation, the focus is on dynamic coarsening of the equilibrium ϑ phase in an Al-4wt pct Cu alloy. For this purpose, specimens containing a uniform ϑ particle distribution have been produced and deformed in compression at two different temperatures (200 °C and 250 °C) and strain rates in the ranges of 200 °C to 250 °C and 10⁻⁵ to 10⁻² s⁻¹, respectively. The particle size distribution measurements performed in a scanning microscope in back-scattered mode demonstrated a double peak behavior depending on temperature: at the lowest test temperature, the dynamic coarsening is enhanced at the highest strain rate, while at 250 °C, the coarsening seems to be affected by crushing of small and medium size particles during straining.     

Effect of temperature and deformation histories on grain coarsening in medium carbon steel

Abstract

Hot rolling of medium carbon steel bars using a prototype mill and numerical analyses were carried out to examine quantitatively the effect of temperature and strain throughout rolling on the final grain size of the product. Cross-sections of the rolled bars were subjected to optical microscopy to investigate the effect of the instantaneous decrease in temperature owing to contact with the roll groove on grain coarsening in the vicinity of the bar surface. By analysing the grain size after rolling, the temperature history throughout rolling, and the equivalent plastic strain after rolling, it was found that the instantaneous decrease in temperature owing to contact did not affect grain coarsening unless the final values of the temperature and strain fell within a narrow band of values meeting the criteria for grain coarsening. Referring to both the present results and the authors' previous studies, criteria have been established for the prevention of grain coarsening in steel bar sizing operations.     

剧烈塑性变形对珠光体钢丝奥氏体转变的影响

 用金相显微镜、扫描电镜、透射电镜、X射线衍射仪、同步热分析仪研究了冷拉拔形变对珠光体钢丝奥氏体化热处理过程和组织的影响。经过冷拉拔剧烈塑性变形后,珠光体组织呈纤维状,其片层沿拉拔轴向排列,厚度剧烈减薄,铁素体<110>丝织构强度达到饱和。经剧烈塑性变形的珠光体在奥氏体化转变时,奥氏体形核更早、更密集,且沿轴向生长;在完成等温转变后,其原奥氏体晶粒、珠光体团尺寸均明显细化,其铁素体<110>丝织构一定程度遗传到了相变后的组织中,但沿拉拔轴向排列的片层形貌特点并未得到遗传。     

Effect of plastic deformation on the physicomechanical properties of tungsten carbide-cobalt hard alloys

Summary A study was made of the effect of prior plastic deformation on the hardness, strength, coercive force, and electrical resistivity of tungsten carbide-cobalt hard alloys containing 10–25% cobalt. Plastic deformation decreases the hardness of the alloys. Up to a deformation of about 5–6%, all the alloys investigated showed a marked drop in hardness. Further deformation did not decrease the hardness of alloy VK25; for the alloys with lower cobalt contents, the hardness decrease was less pronounced.     

Effect of plastic deformation on the fracture energy of powder and cast iron

Conclusions Structurai evolution in powder material is subject to the laws of deformation for cast bcc metals.The fracture energy and cold-brittleness temperature are sensitive to the structural state of the material: change in this predetermines the changes in the fracture energy and cold-brittleness temperature.The nature of the change in fracture energy with degree of deformation is independent of the method of production of the material (cast or powder) and the rolling temperature (below the recrystallization temperature): at low deformations the fracture energy decreases (=0–15%); following this it increases upon formation of a cell structure (=15–30%). With further increase in the degree of deformation (=30–40%) the fracture energy decreases, upon transition to a misoriented cell structure the fracture energy in the rolling plane decreases, but in the transverse plane increases.Translated from Poroshkovaya Metallurgiya, No. 9(345), pp. 74–79, September, 1991.     

轧制塑性变形对W-Cu复合材料组织性能影响

对不同Cu含量[20%～50%(质量分数)]的热挤压后的W-Cu合金坯料进行轧制,通过对比得出最佳轧制工艺参数,并制备出微观组织均匀、致密度高、性能优异的W-Cu合金板材。结果表明:轧制力随着道次轧下量的增加而逐渐增大,并且当一次轧下量超过60%时,轧制力急剧增加;随着轧制变形量的增加,Cu相发生变形,W相形状基本不发生变化,但W相有细化的趋势;轧制变形能在保持W-Cu合金热挤压后高组织均匀性、高致密度、高性能的基础上获得薄板甚至是箔材。     

Effect of plastic deformation on the mechanical properties and the fine-structure parameters of Pb-Ca-Sn alloys

The specific features of structure formation in Pb-Ca-Sn alloys intended for battery current leads are considered. The effect of plastic deformation on the mechanical properties and the fine-structure parameters in Pb-0.1% Ca-0.3% Sn and Pb-0.05% Ca-1.1% Sn alloys is studied. The influence of the initial structure on the mechanical properties and the fine-structure parameters of the alloys is shown, and the variation of the alloy properties under plastic deformation is demonstrated.     

Effect of the morphology of pores on the regularities of plastic deformation of porous bodies. II. Evolution of the shape of pores in the process of plastic deformation

Translated from Poroshkovaya Metallurgiya No. 5(353), pp. 13–18, May, 1992.     

Influence of the temperature on the plastic deformation in TiAl

A new alloy, Ti-48.6Al-1.9Cr-1.9Nb-1B, with a near-equiaxed γ microstructure and with a lamellar microstructure is investigated by compression tests between 20 and 800 °C and transmission electron microscopy (TEM). The yield stress exhibits no anomaly as a function of the temperature, while an anomaly, related to strain hardening, is found at 400 °C in the hardening rate and the activation volume for both the lamellar and nonlamellar structure. Above 700 °C, a change in the deformation mechanism occurs and the material becomes remarkably softer. The TEM micrographs highlight the importance of ordinary dislocation motion for both structures at all temperatures. The comparison with previously reported TEM observations on single-phase TiAl alloys shows definitely that the density of ordinary dislocations is higher in the investigated two-phase TiAl alloy deformed at room temperature. Also, the presence of the lamellar interfaces drastically changes the mechanical properties of the alloy and the deformation mechanism. In contrast to the nonlamellar samples, superdislocations are rare, and twinning is very frequent in the lamellar structure.     

The deformation kinetics theory of the stress dependence of plastic deformation

The fact that plastic deformation is controlled by thermally activated processes leads to the physically rigorous conclusions that the mechanisms are defined either by a single rate constant or by the kinetics combination of rate constants. For the determination of the kinetics—that is, for the establishment of the functional relation of the stress dependence of the work, experiments have to be carried out. When the test results are plotted in the coordinate systems of logarithm of strain rate vs linear stress, also logarithm of strain rate versus linear reciprocal temperature, the behavior exhibited by the two plots defines the nature of the stress dependence of the work. The kinetics analysis of the two representations leads to the functional expression of the constitutive law in physically exact and rigorous expressions. Applications to typical mechanisms are discussed: plasticity limited by discrete obstacles; lattice diffusion controlled creep; dislocation core diffusion controlled creep; plasticity limited by lattice resistance.     

Estimation of plastic deformation in the technologies of bulk cold deformation

A technique for determining the degree of reduction upon forming by cold bulk shaping has been proposed. The technique is based on a comparison of the measurement data on the hardness of a cold-worked metal with that of the same metal subjected to a compression test at a certain strain intensity. The technique has been tested in technological operations of reduction and thread rolling.     

The plastic deformation of TiAl

The deformation substructure of TiAl (Llo type ordered lattice) tested in compression, and the factors determining it were investigated. Two types of dislocations take part in the plas-tic deformation, namely a/2 [110] and a/2 [Oil]. The latter type will disorder the Llo super-lattice and therefore would be expected to move in pairs as superdislocations. Some obser-vations are essentially in agreement with the predictions, however the large proportion and morphology of a/2 [O1l] dislocations observed was unexpected. Twins of the [112] (111) type play an important role in the deformation of the alloy, and the early stages of their formation have been recorded. Finally, equi-Schmid factor lines have been constructed in an attempt to evaluate the importance of the sense of the applied stress on the deformation capability of the alloy. Formerly visiting Scientist at the Aerospace Research Laboratories     

Effects of plastic deformation on the structure of WC-Co alloys

Summary The structural picture is established of strain propagation in the carbide and cobalt phases in VK6 and VK50 hard alloys at loads approaching the yield point of the alloys. Electron-microscopical investigation reveals slip bands in the carbide phase at stresses close to, or equal to, the yield point of the alloys. This is observed both in the low-cobalt VK6 and the high-cobalt VK50 alloys, which may be attributed to their structures being similar in that they both exhibit continuous WC-WC grain contacts.Translated from Poroshkovaya Metallurgiya, No. 5 (77), pp. 63–68, May, 1969.     

Effect of plastic deformation and high pressure working on the structure and microhardness of metallic glasses

The effects of rolling, bending and high pressure working on the structure and microhardness of Fe, FeNi and Co based metallic glasses have been investigated. Some special methods of specimen deformation and microhardness measurement were used. The structure has beeninvestigated by X-ray analysis and positron annihilation methods. A large importance of structural relaxation process occurring at room temperature during some hours after deformation has been established. The correlation between structural changes and those of mechanical properties after deformation has been found. The strain hardening and strain softening of metallic glasses has been found to depend upon the pattern of stressed state under the deformation.