About: Hot working is a(n) research topic. Over the lifetime, 4512 publication(s) have been published within this topic receiving 70521 citation(s).
Abstract: In industrial forming processes, the metals and alloys are subject to complex strain, strain-rate, and temperature histories. Understanding the flow behaviors of metals and alloys in hot working has a great importance for designers of metal forming processes. In order to study the workability and establish the optimum hot formation processing parameters for some metals and alloys, a number of research groups have made efforts to carry out the thermo-mechanical experiments (compressive, tensile and torsion tests) over wide forming temperatures and strain-rates, and some constitutive equations were developed to describe the hot deformation behaviors. This paper presents a critical review on some experimental results and constitutive descriptions for metals and alloys in hot working, which were reported in international publications in recent years. In this review paper, the constitutive models are divided into three categories, including the phenomenological, physical-based and artificial neural network models, to introduce their developments, prediction capabilities, and application scopes, respectively. Additionally, some limitations and objective suggestions for the further development of constitutive descriptions for metals and alloys in hot working are proposed.
15 Jan 2002-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
Abstract: Constitutive equations including an Arrhenius term have been commonly applied to steels with the objective of calculating hot rolling and forging forces. The function relating stress and strain rate is generally the hyperbolic-sine since the power and exponential laws lose linearity at high and low stresses, respectively. In austenitic steels, the equations have been used primarily for the peak stress (strain) associated with dynamic recrystallization (DRX) but also for the critical and steady state stresses (strains) for nucleation and first wave completion of DRX. Since the peak strain is raised by the presence of solutes and fine particles, the stress is raised more than by simple strain hardening increase, thus causing a marked rise in activation energy in alloy steels. In contrast, large carbides, inclusions or segregates, if hard, may lower the peak strain as a result of particle stimulated nucleation. Due to the linear relation between stress and strain at the peak, flow curves can be calculated from the constitutive data with only one additional constant. Maximum pass stresses can also be calculated from a sinh constitutive equation determined in multistage torsion simulations of rolling schedules. Comparison is made between carbon, micro-alloyed, tool and stainless steels and to ferritic steels which usually do not exhibit DRX. Parallels to the effects of impurities and dispersoids on the constitutive equations for Al alloys are briefly discussed.
Abstract: The high temperature deformation of nickel and three nickel-iron alloys has been studied between 0.6 and 0.9 Tm over a wide range of constant strain rates in torsion. It is established from metallographic and flow stress observations that dynamic recrystallization occurs at strains greater than a critical value and results in a recrystallized grain size which is determined entirely by the flow stress. The kinetics of dynamic recrystallization are discussed and shown to be in agreement with experimental observations. It is concluded that the activation energy for deformation is determined by recrystallization and that recrystallization is periodic at low stresses but becomes continuous with increasing stress.
Lallit Anand1•Institutions (1)
Abstract: Elevated temperature deformation processing - “hot-working,” is an important step during the manufacturing of most metal products Central to any successful analysis of a hot-working process is the use of appropriate rate and temperature-dependent constitutive equations for large, interrupted inelastic deformations, which can faithfully account for strain-hardening, the restoration processes of recovery and recrystallization and strain rate and temperature history effects In this paper we develop a set of phenomenological, internal variable type constitutive equations describing the elevated temperature deformation of metals We use a scalar and a symmetric, traceless, second-order tensor as internal variables which, in an average sense, represent an isotropic and an anisotropic resistance to plastic flow offered by the internal state of the material In this theory, we consider small elastic stretches but large plastic deformations (within the limits of texturing) of isotropic materials Special cases (within the constitutive framework developed here) which should be suitable for analyzing hot-working processes are indicated
Abstract: The main feature of hot working is that extremely large strains are applied to materials at high rates of strain at temperatures above ∼ 0.6Tm, where Tm is the melting temperature in degrees Kelvin. Strength and ductility under these conditions are markedly dependent on both temperature and rate of straining. Although this review is confined to strength and structure during hot working, ductility is intimately related to the deformation processes that govern plastic flow. This aspect has been recently reviewed by one of the authors. These large strains can be achieved with little or no strain-hardening, indicating that dynamic softening processes can operate sufficiently rapidly to balance the strain-hardening processes. In this situation, the structural changes involved can be used to obtain information on the mechanism of deformation. However, as emphasised later, care must he taken in the interpretation of such hot-worked structures, since significant structural changes can occur on holding at ...