Development of a Processing Map for Use in Warm-Forming and Hot-Forming Processes
01 Jun 1981-Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science (Springer-Verlag)-Vol. 12, Iss: 6, pp 1089-1097
TL;DR: In this article, a fracture initiation map is developed which should be useful in fast forming operations at strain rates greater than about 10-3 s-1 at elevated temperatures, and two types of cavitation mechanisms, one pertaining to cavity formation at second phase particles, as in ductile fracture, and the other pertaining to wedge type microcracking at grain boundaries, are considered.
Abstract: A fracture initiation map is developed which should be useful in fast forming operations at strain rates greater than about 10-3 s-1 at elevated temperatures. Two types of cavitation mechanisms, one pertaining to cavity formation at second phase particles, as in ductile fracture, and the other pertaining to wedge type microcracking at grain boundaries, are considered. In addition, dynamic recrystallization and adiabatic heating effects are considered. When these concepts are applied to aluminum, it is shown that there may be an intermediate region in the strain rate and temperature field in which neither of these mechanisms should operate and within which the material would, therefore, be safe from fracture.
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TL;DR: In this article, a new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented, which considers the workpiece as a dissipator of power in the total processing system and evaluates the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ).
Abstract: A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.
1,121 citations
TL;DR: Bulk metal working processes are carried out at elevated temperatures where the occurrence of simultaneous softening processes would enable the imposition of large strains in a single step or multi-step process.
Abstract: Bulk metal working processes are carried out at elevated temperatures where the occurrence of simultaneous softening processes would enable the imposition of large strains in a single step or multi...
622 citations
TL;DR: In this article, the fabrication and mechanical investigation of aluminium alloy, alumina (Al2O3) and boron carbide metal matrix composites is discussed, where the fabrication is done by stir casting which involves mixing the required quantities of additives into stirred molten aluminium.
244 citations
Cites background from "Development of a Processing Map for..."
...Raj [15] developed Ashby’s concept of maps to construct a processing map, which represent the limiting for cavity formation at hard particles in a soft matrix occurring at lower temperatures and higher strain rates and vice versa....
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TL;DR: In this article, the development and widespread use of thermomechanic processes are considered as one of the oldest and most important materials related technologies, and new materials technologies centre on the development, widespread use, and adoption of such technologies.
Abstract: Forming and forging processes are among the oldest and most important materials related technologies. New materials technologies centre on the development and widespread use of thermomechan...
167 citations
20 Aug 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a hot deformation behavior of AISI 410 martensitic stainless steel was investigated by conducting hot compression tests at the temperatures of 900-1150°C and the strain rates of 0.001-1 s −1.
Abstract: Hot deformation behavior of AISI 410 martensitic stainless steel was investigated by conducting hot compression tests at the temperatures of 900–1150 °C and the strain rates of 0.001–1 s −1 . The relation between the flow stress and Zener–Hollomon parameter was successfully analyzed via the hyperbolic sine function under the whole range of deformation condition. Therefore, the value of apparent activation energy and the empirical materials constants of A and n were determined. The values of both strain and stress of peak and steady state flow were related to Zener–Hollomon parameter and pertaining relations were proposed. On the basis of dynamic materials model the power dissipation map and the instability map were developed. The processing map was obtained by superimposition of the power dissipation and the instability maps and the regions having the lowest strain rate sensitivity added for more clarification of low and high workability regions. Optical microscopy observations of prior austenite grains showed that dynamic recrystallization grain size had an adverse relation with Zener–Hollomon parameter. According to grain size measurements, the best relation between dynamic recrystallization grain size and Zener–Hollomon parameter was proposed.
151 citations
References
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TL;DR: In this paper, a theoretical analysis of the process of the generation of the groove based on anisotropic plasticity theory is presented, and the system of equations derived was solved numerically with the aid of a computer, which enabled the limiting strain of the sheet metal to be determined as a function of the material.
1,814 citations
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TL;DR: In this article, the authors investigated the permitted discontinuities of stress, velocity, and surface slope in a plastic-rigid sheet deformed in its plane, and the necessary restrictions on the stress-state and rate of workhardening were obtained for any yield function and plastic potential.
Abstract: Permissible discontinuities of stress, velocity, and surface slope are investigated in a plastic-rigid sheet deformed in its plane. One such discontinuity of velocity is shown to be the mathematical idealization of localized necking; the necessary restrictions on the stress-state and rate of workhardening are obtained for any yield function and plastic potential. The results are illustrated by an examination of the modes of necking in notched tension strips. The constraint factors at the yield point are obtained for notches with wedge-shaped or circular roots.
1,243 citations
TL;DR: In this paper, it is established from metallographic and flow stress observations that dynamic recrystallization occurs at strains greater than a critical value and results in a recrystized grain size which is determined entirely by the flow stress.
498 citations
TL;DR: In this paper, the temperature dependence of internal friction and rigidity modulus of 99.991 percent aluminum have been measured as a function of frequency of torsional vibration and grain size of the specimen.
Abstract: In order to elucidate further the concept of relaxation of shear stress across grain boundaries in metals, the temperature dependence of internal friction and rigidity modulus of 99.991 percent aluminum have been measured as a function of frequency of torsional vibration and as a function of grain size of the specimen. It has been found that for the same specimen, an increase of frequency of vibration shifts the internal friction curve and the rigidity relaxation curve (${Q}^{\ensuremath{-}1}$ and $\frac{G}{{G}_{U}}$ versus temperature) to higher temperatures; and when the frequency of vibration is kept constant, a change in grain size of the specimen has the same effect as a change of the frequency of vibration The observed internal friction and rigidity relaxation can be expressed as functions of the parameter $(\mathrm{G}.\mathrm{S}.)\ifmmode\times\else\texttimes\fi{}f\ifmmode\times\else\texttimes\fi{}\mathrm{exp}(\frac{H}{\mathrm{RT}})$, where (G.S.) is the grain size or average grain diameter of the specimen, $f$ is the frequency of vibration, and $H$ is the heat of activation. It is shown that all these observed phenomena are necessary manifestations of the stress relaxation across grain boundaries arising from the viscous behavior of the grain boundaries in metals, which behavior has been demonstrated by previous anelastic-effect measurements.
165 citations