Effect Of Superplastic Deformation Research Articles

Effect of superplastic deformation on microstructures, texture, and mechanical properties of 2A97 Al–Cu–Li alloy

In the present study, the effect that superplastic deformation exerts on the microstructures, texture, and mechanical properties in 2A97 Al–Cu–Li alloy was investigated. The as-received material was deformed to a series of strains for 50%, 100%, 150%, and 200% at 430 °C with an initial strain rate of 2 × 10−3 s−1, and the grain structure, dislocation, secondary phase particles, cavities, texture, and tensile properties of deformed alloys were demonstrated and discussed comprehensively. Results show that with the increase of superplastic strain, the grain size of the alloy decreased gradually due to the dynamic recrystallization, and the Cu-rich secondary phase particles partially dissolved and partially coarsened. The initiation and growth of the cavities mainly depended on the grain boundary sliding and grain rotation, the fraction of cavities increased rapidly at higher strains (100%–200%). Superplastic deformation weakened the rolling texture (Brass, Copper, and S) and enhanced the recrystallization texture (Goss and ND-Rotated-Cube). The strength of the material decreased with increasing the superplastic strain firstly, after the strain exceeded 100%, the strength started to increase. The fracture elongation varied oppositely. The strengthening mechanism was discussed in detail. The coarsening of Cu-rich secondary phase particles and the rapid formation of cavities resulted in the drastic loss in ductility after the strain of 100%.

Effect of superplastic deformation on precipitation behavior of sigma phase in 3207 duplex stainless steel

Owing to excellent strength, toughness and corrosion resistance, duplex stainless steels (DSS) are widely used in constructional and petrochemical applications. Sigma phase, which has detrimental impact on the properties, is readily precipitated during hot working of DSS. However, precipitation behavior of sigma phase during superplastic deformation, which is the most significant processing method of DSS, is still unclear. In the current study, the effect of superplastic deformation on the precipitation behavior of sigma phase was investigated in 3207 duplex stainless steel. The result shows that superplastic deformation could prevent sigma phase precipitation generally by increasing mobility of grain boundaries and decreasing misorientation of the sigma phase boundaries, resulting in some sigma phase precipitated on the twin boundaries. Most of the sigma phase precipitated on ferrite-austenite interface with misorientation of 20–25°, while it precipitated in ferrite or austenite with the misorientation of 40°–45°. The orientation relationship between sigma phase and matrix matched well in austenite and on the ferrite/austenite interfaces, while it showed a small misfit in ferrite. The prevention effect of the superplastic deformation on the sigma phase precipitation was beneficial to quasi stable deformation stage, resulting in longer elongation.

Effect of superplastic deformation on microstructure evolution of 3207 duplex stainless steel

High temperature tensile, electron backscatter diffraction (EBSD) techniques and transmission electron microscope (TEM) were combined to perform a systematic investigation for superplastic deformation behavior, mechanism and microstructure evolution of 3207 duplex stainless steel. Excellent superplasticity of this alloy is indicated by the elongation indicates and the flow curves revealing four stages of deformation: elastic deformation stage, stable deformation stage, quasi-stable deformation stage and localized necking stage. Before the initial of quasi-stable deformation stage, several low angle boundaries (LAGBs) can be observed, indicating dislocation creep-controlled deformation is the dominant mechanism. In the middle and final of the quasi-stable deformation stage, LAGBs are found evolving into high angle boundaries (HAGBs) indicating the dominant deformation mechanism to be grain boundary sliding (GBS), leading to the weakened textures. In the localized necking stage, dislocations are found generated by the combination of cavities along grain boundaries, indicating the dominant deformation mechanism of GBS and an accommodation mechanism of conventional plastic deformation. The main softening mechanism responsible for the flow behaviors of the 3207 duplex stainless steel is identified as dynamic recrystallization (DRX), which completely neutralized the effect of work hardening at the quasi-stable deformation stage.

Effect of superplastic deformation on the microstructure and orientation of austenite in 3207 duplex stainless steel

Effect of superplastic deformation on the microstructure and orientation of austenite in 3207 duplex stainless steel

Effect of superplastic deformation on the bonding property of 00Cr25Ni7Mo3N duplex stainless steel

The superplastic deformation diffusion bonding of 00Cr25Ni7Mo3N duplex stainless steel was performed on a hot simulator. The microstructure of the bonding interface was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The mechanical properties of the specimen were investigated by a shear strength test. The results indicated that the shear strength was improved with the increase of superplastic deformation reduction. When the deformation reduction was up to 50%, the shear strength of the specimen achieved 417 Mpa, approaching to that of the base metal. In addtion, the superplastic diffusion bonding technique was not very sensitive to surface roughness levels. When the surface roughness of the bonding specimen surpassed 0.416 μm (level G2), the shear strength achieved at least 381 MPa.

Effect of Superplastic Deformation on the Properties of Zirconia Dispersed Alumina Nanocomposite

In this paper constrained extrusion of the zirconia dispersed alumina nanocomposite under superplastic conditions was conducted. The mechanical properties of deformed material were studied and its results were compared with those of the initial materials. The microstructure evolution during superplastic deformation was also analyzed. The results demonstrated that after superplastic extrusion the flexural strength, relative density, Vickers hardness as well as fracture toughness of the material increased noticeably. The flexural strength of the deformed composite even retained at a high value of 310MPa at 800°C. The fracture toughness of the material increased from 6.92 MPa·m1/2 to 8.87 MPa·m1/2 after deformation. After superplastic extrusion due to grain boundary sliding and the compressive stress state, the internal porosities in as-sintered materials were eliminated. During extrusion with grain coarsening the effect of t-ZrO2 to m-ZrO2 transformation toughening increased because more zirconia grains reached the critical dimension. Although grain coarsening may cause the decrease of the fracture toughness in some extent, the phase transformation toughening and strengthening dominated. As a result, the mechanical properties of the deformed material were improved.

Effect of Superplastic Deformation on Thermal Expansion Behavior of Tetragonal Zirconia Polycrystals

Three mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) were superplastically deformed under various conditions and microstructural evolution was characterized. Thermal expansion properties of the 3Y-TZP specimens were then measured by a push-rod type dilatometer in a temperature range from 300 K to 1473 K. Experimental results showed that the mean coefficient of linear thermal expansion, α, decreased with an increase in the volume fraction of cavities. The cavity dependence of α value was dependent on temperature and was weakened with an increase in temperature. Changes in the average grain size and grain aspect ratio due to the superplastic deformations were found to have little effect on the thermal expansion property within the present experimental range.

Effect of microstructure on tensile and fatigue properties of superplastically formed Al–Li–Cu–Mg–Zr 8090 alloy sheet

The effect of super plastic deformation on the microstructure of the low density Al–Li–Cu–Mg–Zr (8090) alloy has been investigated. Changes in grain structure, grain misorientation, and texture were observed with increasing superplastic deformation. These observations are consistent with strain enhanced grain growth accompanied by grain boundary sliding and rotation. The tensile and fatigue properties of superplastically formed (SPF) 8090 depend on superplastic strain, post-form heat treatment, and copper content. It is shown that, in the heat treated condition, the continuous loss in strength with superplastic strain can be attributed to grain growth and solute depletion at the surface. The changes in grain structure lead to increased surface roughness and a consequent reduction in fatigue life. In alloys of high copper content precipitation during age hardening is additionally dependent on the rate of cooling after SPF.MST/1286

Effect of microstructure on tensile and fatigue properties of superplastically formed Al–Li–Cu–Mg–Zr 8090 alloy sheet

AbstractThe effect of super plastic deformation on the microstructure of the low density Al–Li–Cu–Mg–Zr (8090) alloy has been investigated. Changes in grain structure, grain misorientation, and texture were observed with increasing superplastic deformation. These observations are consistent with strain enhanced grain growth accompanied by grain boundary sliding and rotation. The tensile and fatigue properties of superplastically formed (SPF) 8090 depend on superplastic strain, post-form heat treatment, and copper content. It is shown that, in the heat treated condition, the continuous loss in strength with superplastic strain can be attributed to grain growth and solute depletion at the surface. The changes in grain structure lead to increased surface roughness and a consequent reduction in fatigue life. In alloys of high copper content precipitation during age hardening is additionally dependent on the rate of cooling after SPF.MST/1286

Effect of superplastic deformation on microstructure, texture, and tensile properties of Ti–6AI–4V

The fine grained, equiaxed duplex α/β phase microstructure of Ti–6AI–4V alloy enables large uniform plastic strains to be obtained under superplastic conditions. In this paper the role of microstructure and texture in superplastic deformation is considered. A banded, two phase microstructure gives rise to anisotropic superplastic flow stresses and strains, and can affect post-formed mechanical properties. The effect of microstructure is discussed with reference to the behaviour of Ti–6AI–4V alloy in various product forms: thick and thin sheet, extruded section and tube, and rolled bar. Manufacturing costs may dictate the use of fusion welding or diffusion bonding before superplastic forming, and the effect of such joints on deformation is described. The above data are related to other published work on Ti alloys, and the implications for the manufacture of components by superplastic forming are considered.MST/1328

Effect of superplastic deformation on microstructure, texture, and tensile properties of Ti–6AI–4V

The fine grained, equiaxed duplex α/β phase microstructure of Ti–6AI–4V alloy enables large uniform plastic strains to be obtained under superplastic conditions. In this paper the role of microstructure and texture in superplastic deformation is considered. A banded, two phase microstructure gives rise to anisotropic superplastic flow stresses and strains, and can affect post-formed mechanical properties. The effect of microstructure is discussed with reference to the behaviour of Ti–6AI–4V alloy in various product forms: thick and thin sheet, extruded section and tube, and rolled bar. Manufacturing costs may dictate the use of fusion welding or diffusion bonding before superplastic forming, and the effect of such joints on deformation is described. The above data are related to other published work on Ti alloys, and the implications for the manufacture of components by superplastic forming are considered.MST/1328

Effect of superplastic deformation using different stress modes on the structure of high-speed steels

1. During superplastic deformation (SPD) of steel R6M by tension, up setting, and direct extrusion a more dispersed structure develops as a result of refinement and spheroidizing of the carbide phases and an increase in the uniformity of their distribution. This effect occurs to a greater extent during tension loading. 2. In powdered steel 10R6M5-MP, which possesses a greater degree of initial dispersion and uniform distribution of the carbide phases than in steel R6M5, there also occurs an increase in the dispersion and uniform distribution of the carbide phases. However, this effect is only observed during SPD by tension and upsetting. During direct extrusion of steel 10R6M5-MP the dispersion and uniform distribution of the carbide phases remain at the same level they were in the initial condition or become less so with increase in the compressive stress level. 3. The greatest degree of increased dispersion and uniform distribution of the carbide phases in high-speed steels R6M5 and 10R6M5-MP occurs during SPD by tension loading. 4. The more dispersed the initial structure, than the more strongly do compressive stresses inhibit diffusion processes. 5. Changes in the superplastic indices during transfer from tension to compression loading may be associated with a change in the contribution of diffusion creep to the superplastic process. 6. The increased dispersion and uniform distribution of the carbide phases in high-speed steels R6M5 and 10R6M5-MP due to SPD is a function of the initial dispersion and uniform distribution of the carbides and of the type of stress scheme used.

Effect of superplastic deformation on the distribution of alloying elements in steels R6M5 and 10R6M5-MP

1. Superplastic deformation improves the uniformity of distribution of W, V, Mo, and Cr in the high speed steels R6M5 and 10R6M5-MP. 2. The degree of uniformity of distribution of alloying additives depends on the initial (liquation) nonuniformity of the steel and on the level of SPD which characterizes the activity of the occurring diffusion processes.

Effect of superplastic deformation on the grain size and tensile properties of Al-6.2Zn-2.5Mg-1.7Cu (7010) alloy sheet

An Al-Zn-Mg alloy (7010) was cold-rolled and annealed to produce a small recrystallized grain size, and superplastically deformed in the temperature range 475 to 520° C at strain rates $$\dot \varepsilon = {\text{1}}{\text{.1 x 10}}^{{\text{ - 5}}} $$ to 2.8×10−3 sec−1. At 500° C and $$\dot \varepsilon = {\text{2}}{\text{.8 x 10}}^{{\text{ - 5}}} $$ sec−1 superplastic elongations up to 350% were obtained, but above about 60% elongation the residual room-temperature tensile properties after heat treatment decreased due to increasing grain-boundary cavitation. Grain growth rates were increased by superplastic strain.

The Effect of Superplastic Deformation on Subsequent Service Properties of Fine Grained 7475 Al

Intergranular cavitation may be a limiting factor in the otherwise highly promising commercial exploitation of the recently developed superplastic forming process for the high strength aluminum alloy, 7475. A preliminary investigation has been carried out to quantify the effects of superplastic deformation on the major ambient temperature service properties. It is shown that the properties most degraded by the development of cavitation after large superplastic strains are those that depend on the local strain at tensile fracture. This affects, mainly, ductility and fatigue life. However, the effects are not generally significant below effective superplastic strains of about 0.8 to 0.9 (120–150 percent elongation) with the optimum forming conditions (T=516°C, ε˙=2×10−4 s−1). Furthermore, since the fine grain processing has an initial beneficial effect on the ductility-related properties, compared to conventionally processed sheet, most superplastically formed components would suffer very litle, if any, design penalties.

Effect of superplastic deformation on the structure and properties of alloy MA21

1. Superplastic deformation improves the strength characteristics of alloy MA21. 2. Treatment under conditions of superplasticity makes it possible to obtain a condition of the alloy characterized by structural homogeneity and even distribution of the alloying elements. 3. There is a substantial correlation between the structure of the alloy after various treatments and the stability of the mechanical properties.

Effect of superplastic deformation on the structure of heat-resistant nickel alloy ZhS6KP

1. Deformation of heat-resistant nickel alloy ZhS6KP in tension under conditions of superplasticity leads to changes in the quantity and size of γ′ phase, which can be explained by the intensification of diffusion processes during superplastic deformation. 2. The formation of centers of fracture in samples of alloy ZhS6KP during superplastic deformation is due to carbide stringers.