Effect of hich-temperature thermomechanical treatment on mechanical properties of 45KhNMFA steel in torsion

High-temperature thermomechanical treatment involving deformation in torsion ensures a substantially larger increase in the fatigue limit of steel carrying pulse torsion loads than the ordinary quench-hardening treatment. Rapid electrical resistance heating for quenching also has a beneficial effect on the fatigue strength. Oriented strain hardening of specimens subjected to a high-temperature thermomechanical treatment produces an additional increase in their fatigue strength in torsion.     

Influence of torsion deformation on microstructure of cold-drawn pearlitic steel wire

A comparative microstructural analyse of cold-drawn pearlitic steel wires in as-drawn and after an additional torsion deformation states is presented in this paper. During torsion the temperature of the wire increases to attain 90 °C. Then the microstructure of wires is the result of different events effects, as initial drawing, temperature increase and torsion deformation. Individually or in association, both events influence the stress level and nature in ferrite and cementite lamellae, modify the kinetic of cementite decomposition and change the dislocation mobility in cementite and ferrite. Carbon atoms migration from cementite to ferrite is affected by these thermomechanical treatments inducing a modification of dislocation pinning by carbon atoms and lamellae interfaces. The phases’ determination and quantification, associated with the carbon content variation in each phase was investigated by Mössbauer spectroscopy. The evolution of the pearlitic steel wires microstructure will be discussed point-by-point, as a function of applied deformation nature.     

The effect of strain aging on the stability of rod elements

The article suggests a thermomechanical method of enhancing the stability of various structures that includes preliminary plastic deformation with subsequent aging and elevated temperatures. The results of experiments with longitudinal compression of a rod and torsion of a thinwalled cylindrical specimen showed that this method leads to increased torsional load and critical moment of loss of stability, on an average by 20%.Translated from Problemy Prochnosti, No. 10, pp. 9–11, October, 1994.     

Microstructures of 18R martensite induced by deformation and thermomechanical cycles in CuZnAl shape memory alloy

Microstructures of martensite in a Cu-26.4Zn-4.8Al shape memory alloy after deformation and thermomechanical cycles are reported. By detailed transmission electron microscopy investigation, it is clearly established that the microstructure induced by deformation is different from that induced by thermomechanical cycles, and the effects on the thermoelastic martensite transformation are also not the same at all. The microstructure of martensite induced by deformation is mainly deformation twins when the deformation exceeds the range of recoverable strain of the shape memory alloy. The main microstructure characteristic of martensite which has undergone thermomechanical cycles is regularly distributed dislocations, which are mainly aligned but sometimes tangled. Micro-twins similar to those found in deformed martensite and crossed bands also exist inside the martensite of samples after thermomechanical cycles, but the amounts are too small to be regarded as important microstructure features.     

形变热处理细化7475Al合金的晶粒

本文提出了一种细化7475Al 合金晶粒的简化工艺。该工艺由固溶处理、轧制及再结晶组成。该工艺适合于工业生产。经过细化后的7475Al 合金平均晶粒尺寸可以达到10μm,具有优良的超塑性能。     

Influences of thermomechanical treatments on the cryogenic treatability of a slightly unstable austenitic stainless steel

The success of deep cryogenic treatment (DCT) of austenitic stainless steels (AusSSs) relies heavily on martensitic transformation. For AusSSs that are not prone to martensitic transformation, thermomechanical treatments (such as high-temperature solution treatment, plastic deformation, and sensitisation) may expedite DCT by encouraging martensite formation. This paper looks into the influences of the aforementioned thermomechanical treatments on the cryogenic treatability of a slightly unstable AusSS regarding tensile properties. Overall, no noticeable strengthening could be achieved through DCT, but a slight improvement in ductility was observed for all the thermomechanical treatment conditions mentioned above. Preliminary results indicated that the pitting corrosion resistance of the AusSS was almost unaltered by DCT.     

H型截面钢梁约束扭转的简化计算

钢梁在外扭矩以及梁端约束的作用下,会产生翘曲正应力以及剪应力,传统上利用扇性坐标及双力矩法计算,计算过程很繁琐。许多工程师在设计中对钢梁扭转作用的处理带有一定的盲目性。根据约束扭转的受力及变形特点,以变形协调为基础提出一种新的计算钢梁约束扭转的简化计算方法,该方法可很好的计算钢梁在外扭矩作用下的受力情况。算例计算结果表明,该方法具有很好的精度和准确性,可供工程设计应用。     

Effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy

The CuCrZr alloy undergoes processes of precipitation during ageing. Besides precipitation hardening the strength is affected by cold deformation which is performed before and after ageing. The cold deformation (D ₁) before ageing accelerates the process of strength hardening, since it induces higher rate of precipitation from the saturated a-sold solution. Cold deformation (D ₂) after ageing primarily affects the alloy strength. In this paper the results of the effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy are presented. The aim of the paper was to evaluate the most suitable combination of thermomechanical treatment and alloy properties.     

Brittle-to-ductile transition in the fracture of steels hardened by thermomechanical treatment

This article describes the results of a comparative study of the brittle-to-ductile transition observed during the fracture of steel after quench-hardening and after thermomechanical treatment, with respect to the tempering and test temperatures. Substantial differences in the kinetics of the increase in ductility during the brittle-to-ductile transition were revealed by mechanical torsion tests and electron microscopic examination of fracture surfaces.     

Stress-corrosion cracking of thermomechanically treated steels

The effect of high-temperature thermomechanical treatment (HTMT) on the susceptibility of high-strength chromium-silicon steels to stress-corrosion cracking was studied. The considerable improvement produced by this treatment was attributed to the resulting reduction in the sensitivity of steels of this kind to the presence of notches formed by corrosion under stress. Comparison of results obtained for specimens tested in tension and torsion made it possible to assess various theories of long-term strength for heat-treated steel (quench-hardened and subjected to low-temperature tempering) under the influence of corrosive media.     

Precipitation behavior and strengthening effect in thermomechanical treatments of Al‐Zn‐Mg alloys

Abstract

An investigation was carried out to determine the precipitation behavior and strengthening effect in various thermomechanical treatments of Al‐Zn‐Mg alloys containing high Zn and low Mg contents. The results show that the precipitation behavior is largely influenced by a plastic deformation in the thermomechanical treatment, and the final precipitate and dislocation structures are greatly related to the influenced precipitation behavior; hence the strengthening effect is determined. Different alloy contents also cause different influences. A super‐strengthening occurs in the T‐AHA (80°C) treatment attributed to the optimum combination of dislocation and precipitate structure.     

Thermomechanical Coupling Model for a Stainless Steel-Clad Plate on Heat Treatment

Strength of Materials - Quick and correct prediction of the internal stress and deformation of stainless steel-clad plates on heat treatment is a problem of specific interest. A thermomechanical...     

Propagation of rayleigh waves in transversely isotropic generalized thermoelastic diffusion

This paper is devoted to the study of propagation of Rayleigh waves in a homogeneous, transversely isotropic, thermoelastic diffusive half-space that is subjected to stress-free, thermally insulated/isothermal, and chemical potential boundary conditions in the context of the generalized theory of thermoelastic diffusion. The Lord and Shulman theory, where thermal and thermomechanical relaxation as well as diffusion relaxation are governed by two different time constants, is selected. Secular equations for surface wave propagation in the considered media are derived. The amplitudes of surface displacements, temperature change, and concentration are computed. The paths of the surface particles are determined. Transverse isotropy and diffusion effects on the phase velocity, group velocity, and attenuation coefficient are presented graphically.     

Enhanced Homogenization Strategy by Electroslag Remelting of High‐Manganese TRIP and TWIP Steels

In the production of high‐manganese TRIP and TWIP steels, significant micro‐segregation effects are observed after solidification. Homogenization can be achieved by heat treatment followed by deformation at a significant time and effort (forging, annealing, hot rolling). In an attempt to achieve the best homogeneous microstructure and reduced thermomechanical processing, the cast alloy is treated by electroslag remelting (ESR). After a simple hot rolling procedure with a thickness reduction of 90% and without further heat treatment, micro‐segregation of manganese can be reduced to about 5 wt%. There is a potential to achieve even lower values with further optimization of the ESR process and an adapted thermomechanical processing.     

Modified torsion coefficients for a 3-D brick Cosserat point element

A simple deformation field associated with an exact torsion-like solution of the equilibrium equations of linear elasticity is shown to provide a good approximation of the deformation field in interior elements of a mesh that models pure torsion of a right cylindrical bar with rectangular cross-section. Using this solution, modified torsion coefficients are proposed for a 3-D brick Cosserat point element (CPE) which are shown to improve convergence properties for solutions of pure torsion.     

BEAM STIFFNESS MATRIX BASED ON THE ELASTICITY EQUATIONS

A new general beam stiffness matrix which accounts for bending, torsion and shear deformation is derived from an elasticity solution of the beam. The influence of shear and torsion is considered using a 3×3 matrix of deformation coefficients. Numerical examples are presented to demonstrate the behaviour of the deformation coefficients and of the beam stiffness matrix. © 1997 by John Wiley & Sons, Ltd.     

扭弯比对SRC柱抗震性能影响的试验研究与分析

为研究扭弯比对弯曲和扭转复合作用下型钢混凝土组合（SRC）柱的受力及变形性能影响,以扭弯比为主要控制参数对7个SRC柱进行了弯矩和扭矩成比例加载的低周往复试验,研究分析了扭弯比对SRC柱的破坏特征、滞回性能、承载力以及变形等特征的影响规律,并建立了SRC柱在弯扭复合作用下的抗弯、抗扭承载能力及变形计算方法。研究结果表明:扭弯比是影响SRC柱抗震性能的主要参数,扭弯比参数决定了SRC柱的破坏类型;弯扭复合作用降低了SRC柱的抗弯、抗扭承载能力,但扭弯比对弯曲和扭转存在相反的影响;弯矩与扭矩成比例往复加载相比定扭矩弯矩往复加载,抗弯和抗扭承载力的相互影响程度减小且偏于安全。     

Ultrafast heating and thermomechanical coupling induced by femstosecond lasers

This work focuses on the ultrafast thermomechanical waves generated by the hot electrons excited by ultrafast, ultra-intense lasers. The dominating effects during the short-time transient, including ultrafast thermalization and relaxation between electrons and phonons, result in thermomechanical coupling that cannot be described by Fourier’s law alone. The various thermomechanical properties are grouped to characterize the ultrafast heating and deformation. A finite-difference differential formulation is used as a general tool to tackle the new set of coupled equations that are formulated to describe the severe impingement of a hot-electron blast in the presence of nonequilibrium heating, rapid expansion/contraction of the metal lattices, phonon relaxation, and thermomechanical coupling.     

3Cr2W8V钢形变热处理研究

3Cr2W8V钢广泛应用于有色金属热锻、热挤压和压铸成形.为进一步挖掘3Cr2W8V钢的使用潜力,提高模具材料综合使用性能和使用寿命,本文开展了针对该钢的形变热处理研究,讨论了形变温度、冷却方式及回火温度对试样组织与性能的影响.研究表明高温形变热处理不适宜于3Cr2W8V,形变后水冷优于空冷,并得出组织性能俱佳的优化形...     

转炉用变截面自平衡式扭力杆扭转变形的理论计算

扭力杆通过弹性扭转变形储备能量的大小对氧气顶吹转炉大型设备工作的可靠性有着重要影响,研究其扭转变形成为关键的技术问题之一。该文基于圆柱弹性扭转初等理论,推导了由等截面圆杆、变截面锥杆和过渡圆角三部分共同组成的自平衡式扭力杆的扭转变形的理论计算公式,并以150t转炉用自平衡式扭力杆为例,对其正确性采用有限元方法进行了验证,两种方法的计算结果吻合。该自平衡式扭力杆的实际应用也表明该文两种研究方法都是可行的,但是解析法比有限元法简单方便,更适合工程设计人员直接使用。