Semi-solid Deformation Behavior Research Articles

Semi-Solid Deformation Behavior, Flow Stress Prediction and Deformed Microstructure of GH3536 Superalloy

In current work, the deformation behavior and deformed microstructures of GH3536 superalloy in semi-solid state were investigated, and the semi-solid flow stress was predicted by artificial neural network (ANN) model. The semi-solid compression deformation was carried out at 1320-1350 °C, and the solid deformation behavior at 1200 °C was tested for comparison. The peak stress under 0.01-1 s-1 semi-solid deformation was 45.6-161.9 MPa. The peak stress decreased with the increase of deformation temperature and the decrease of strain rate. The ANN model could well describe semi-solid flow stress. During semi-solid deformation, the apparent viscosity dropped as shear rate increased. At high temperature and low strain rate, more liquid phase was distributed at grain boundaries. The solid grains coarsened as deformation temperature increased.

Microstructure evolution and constitutive modeling of as-cast A356 aluminum alloy in semi-solid deformation regime

The present work deals with the semi-solid deformation behavior of A356 aluminum alloys with an emphasis on microstructure evolution and constitutive modeling. The main idea of this research is based on investigating the semi-solid deformation behavior starting with primary dendritic cast structure, instead the conventional approach in which a feedstock is prepared through the various spheroidization process. Toward this end, hot compression tests in the semi-solid temperature range (580, 590, and 600 °C) under different strain rates (0.001, 0.01, 0.1 s−1) and different initial holding times (1, 7, and 14 min) have been conducted. Compared with the thixotropic deformation in which the solid globules slide within the liquid matrix through lubricated flow mechanisms, in the present case, the strain compensation through the deformation of solid grains was increased. The higher portion of the solid-grains from the applied strain provided a proper condition for substructure development and dynamic recrystallization in the semisolid temperature range. The penetration of the liquid phase along the newly developed boundaries was introduced as another factor influencing on the softening behavior of the material. Under these conditions, the specimens were deformed up to the high strain level (>0.5) without creating cracks or tearing under very low stresses less than 2 MPa. A phenomenological-physical constitutive equation was also developed considering deformation parameters (temperature, strain rate, and strain) and material's parameters (grain size, strain rate sensitivity, viscosity) which was capable of predicting the semisolid flow stress behavior of the material.

Semisolid deformation behavior and processing of CoCrCuxFeNi high-entropy alloys

In this study, the semisolid deformability and processability of three CoCrCuxFeNi high-entropy alloys (x = 1, 2, and 3) were evaluated. At 1175 °C, the Cu content had a major influence on the semisolid deformation due to its control of the liquid fraction. The semisolid alloys displayed a typical pseudoplastic rheological behavior. Only the CoCrCu3FeNi alloy filled the die completely during thixoforming. The Vickers hardness decreased with increasing Cu content due to the different hardness values of the constituent FCC phases. The compression test results showed that the thixoformed CoCrCu3FeNi had good plasticity and a yield stress of 310 MPa. Thus, semisolid processing can be an alternative route for manufacturing components made of high-entropy alloys.

Semi-solid compression of nano/micro-particle reinforced Al-Cu composites: An in situ synchrotron tomographic study

Four-dimensional fast synchrotron X-ray tomography has been used to investigate the semi-solid deformation of nano- and micro-particle reinforced aluminum-copper composites (Al-10 wt% Cu alloy with ~1.0 wt% Al2O3 nano and ~1.0 wt% Al2O3 micro particles). Quantitative image analysis of the semi-solid deformation behavior of three alloys (base, nano- and micro-particle reinforced) revealed the influence of the particulate size on both microstructural formation and dominant deformation mechanisms. The results showed that initial void closure and incubation period were present in the particle-free and nano-particle reinforced Al-Cu composite during semi-solid compression, while the micro-particle reinforced alloy only showed continual void growth and coalescence into cracks. The results suggest that the nano-particle reinforced composite has the best hot-tearing resistance amongst the three alloys. Improved hot-tear performance with nano-particulate reinforcement was attributed to the small liquid channel thickness, fine grain size which alters the distribution/morphology of the liquid channels, more viscous inter-dendritic liquid, and fewer initial voids.

Characterization of semisolid deformation behavior of a high Zr-containing WE magnesium alloy

The effects of temperature and strain rate on the semisolid deformation behavior of a high Zr WE54 magnesium alloys were studied at temperatures of 570, 595 and 620 °C. A flow stress peak was appeared during deformation of the feedstock experimental material at deformation conditions of 570 °C, 0.010 and 0.100 s−1, and 595 °C, 0.100 s−1. The latter results were connected to the occurrence of dynamic recrystallization in solid globules. Also, these conditions were gauged to be able to activate “lubricated flow” mechanism. At 570 °C and strain rate of 0.001 s−1 as well as 595 °C and rates of 0.010 and 0.001 s−1, the flow stress increases and reaches a plateau, where dynamic recovery is considered as the dominant mechanism. However, at 620 °C under all the strain rates, the flow stress drops for a limited strain range and then increases again. The results show that as the liquid removes from the boundaries between the solid parts, the densification of the globules occurs at higher strains, causing an increase in the flow stress. Comparative analysis points out that the feedstock material exhibits a lower flow stress than as-cast alloy associating with a modified morphology of Zr particles after deformation.

Characterization of semisolid deformation behavior and constitutive analysis of Ti230 alloy

The semisolid compressive deformation behavior of Ti230 titanium alloy at the temperature range of 1273 K to 1573 K and strain rate range of 0.005 to 5 s−1 has been investigated by hot compressive testing. The relationship between flow stress and deformation parameters and microstructure were discussed. The results show that the alloy expresses obvious yield point in semisolid state. The maximum decreased with decreasing solid phase fraction and/or decreasing strain rate, and a transition in stress occurred at a solid phase fraction close to 0.95, which is considered to be associated with the decrease in amount of solid bridges between grains and the decomposing effects of the liquid on α-Ti matrix. A deformation constitutive equation for Ti230 alloy in semisolid state was established considering high-temperature deformation activation energy Q. Furthermore, microstructural analysis confirmed that increasing temperature could reduce the deformation-resistant stress and lead to the transformation of softening mechanism from plastic deformation of solid particles (PDS) to sliding between the solid particles (SS).

Effect of Cu concentration on the semi-solid deformation behavior and microstructure of Ti–Cu alloy

The semi-solid compressive deformation behavior of Ti–Cu alloys was investigated by Gleeble-3500 hot simulator at the deformation temperatures ranging from 1273 to 1473 K with strain rates ranging from 5×10−3 to 5×10−1 s−1. The relationship between Cu concentration and flow stress was analyzed, and the deformation apparent activation energy was also calculated. The results show that Cu concentration has significant influence on the flows’ behavior of Ti–Cu alloys, especially at high semi-solid deformation temperatures. The Ti–14Cu exhibits the highest flow stress at 1273 and 1373 K, Ti–2.5Cu alloy exhibits the highest flow stress at 1473 K, and Ti–7Cu alloy shows the lowest flow stress at all tested temperatures, which corresponds to liquid fraction caused by varied Cu concentration and the deformation temperature. The difference in microstructure suggests that the shape and distribution of Ti2Cu precipitates are significantly affected by Cu concentration. The increase in Cu concentration leads to the growth and precipitation of acicular Ti2Cu along grain boundaries at high semi-solid deformation temperatures. The deformation apparent activation energy of Ti–14Cu alloy significantly decreases from solid deformation to semi-solid deformation owing to the change in main deformation mechanism from plastic deformation of solid particles to solid particles’ slippage and rotation of grain boundaries.

Research on the Semi-Solid Compressive Deformation Behavior of Ti-7Cu Alloy

AbstractThe semi-solid deformation behavior of Ti-7Cu titanium alloy in the temperature range of 1,223 K to 1,473 K and strain rate range of 0.005 to 5 s−1 have been investigated by hot compressive testing. The results show that the maximum and stability stresses decrease with decreasing strain rate and increasing temperature. A yielding occurred to the alloy at a higher strain rate under all experimental temperatures. The flow behaviors were described by a constitutive equation based on the Arrhenius equations and the deformation activate energies is also calculated. By comparing with microstructure of the solid deformation, the liquid in semi-solid deformation can overcome the restriction of the movement of solid particle, which reduced the dislocation pile-up during deformation and caused low deformation resistant stress.

The compressive deformation behavior and deformation mechanism of Ti14 alloy in semi-solid state

The semi-solid deformation behavior of Ti14 was investigated using compression tests at deformation temperatures between 1 273 and 1 423 K with strain rate of 5×10−2 s−1. Moreover, the fraction solid at different temperatures was also measured by image analysis. The results showed that the deformation temperature had strong effects on the flow stress, and the stress increased with the decrease of deformation temperature. The maximum stress depended greatly on the fraction solid, and a sharp decrease in stress occurred at a solid fraction between 0.94 and 0.98 (temperature from 1 323 to 1 373 K). This decrease was related to the decrease in the amount of solid bridges between grains. Because of the partial solid/liquid segregation during deformation, the experimental strain rates were much lower than those calculated by the flow of liquid incorporating solid particles, which suggested that the main deformation mechanism between 1 323 and 1 373 K was still plastic deformation of solid particles.

Microstructure evolution and semi-solid deformation behavior of an A356 aluminum alloy processed by strain induced melt activated method

The effects of strain induced melt activated (SIMA) process parameters on the microstructure evolution of an A356 aluminum alloy have been investigated. It is concluded that a fine uniform globular microstructure may be obtained through heating the 45% pre-deformed specimen at 615°C for 6min. In addition, a model for microstructure evolution during SIMA process is proposed. This accounts for the mechanisms causing the microstructural changes in two successive steps of pre-deformation and heating. The present work also explores the semi-solid deformation behavior of the experimental alloy possessing different initial microstructures, including cast, rosette-like, globular and coarsened ones. The applied thixoforming process encompasses a set of isothermal hot compression tests in the semi-solid temperature range. The results indicate that the SIMA processed specimen with globular microstructure exhibits the lowest flow resistance during thixoforming process, followed by those with coarsened, rosette-like and cast microstructures. This has been justified considering the governing deformation mechanisms for different thixoformed microstructures.

Influence of Processing Parameters on the Deformation Behavior of Ti14 Alloy Containing a Small Volume of Liquid

Abstract The effects of the processing parameters on the deformation behavior of Ti14 alloy containing a small volume of liquid have been investigated through compressive tests. Experiments were conducted at deformation temperatures from 1000 to 1150 °C, strain rates from 5×10−3 to 5 s−1 and deformation degrees from 40% to 70%. The results show that deformation temperature and strain rate have significant effects on the peak flow stress. The flow stress decreases with increasing of deformation temperature and/or decreasing of strain rate. The response time required by deformation is affected by the strain rate and liquid fraction is controlled by the temperature. As the temperature increases, deformation mechanism transforms from sliding between solid particles (SS) to the flow of liquid incorporating solid particles (FLS), which improves the semi-solid deformation behavior. In addition, the flow stress decreases with increasing of deformation degrees during the compression which is associated with lubricating effect of liquid during semi-solid deformation.

Deformation Behavior and Constitutive Equation Coupled the Grain Size of Semi-Solid Aluminum Alloy

Isothermal compression tests on Al-4Cu-Mg alloy were carried out in semi-solid state. Deformation behavior and microstructural evolution are discussed in this paper. Meanwhile, a new constitutive equation, which couples the grain size and liquid volume fraction, has been established for the semi-solid deformation behavior. The results show that the maximum difference between the calculated with the experimental data is less than 15%. The present equation is satisfactory for describing the correlation between the flow stress and microstructure of semi-solid Al-4Cu-Mg alloy. The coupled simulation of the deformation behavior and microstructural evolution during the semi-solid forming would be conducted easily through writing the present equation in a FE code.

Research on Semi-Solid Deformation and Forging Behavior of Ti14 Alloy

Titanium and its alloys are widely used in industries due to their excellent comprehensive properties. However, their high-cost limits their applications in civil, therefore the research on low cost titanium technology is necessary. In the present study, the semi-solid deformation behavior of Ti14 burn resistant alloy was investigated. The results indicated that Ti2Cu melting phases within grains and at grain boundaries grow to form coarse grain boundaries and network structures during Ti14 alloy semi-solid deformation. Its microstructure was coarse and the grain boundary was wide after semi-solid forging, leading to low plasticity at room temperature. Recrystallizing heat treatment leads to fine microstructure, which is similar to that of conventional forging, resulting in improvement of tensile mechanical properties. The mechanical properties of semi-solid forging are similar to that of conventional one at high temperature.

Semisolid Extrusion of Low-Carbon Steel

The semisolid state behavior and semisolid extrusion properties of low-carbon steel were investigated, focusing on the possibility of clarifying a semisolid-forming process. First, the cooling curve of low-carbon steel is assessed by thermal analysis, so as to clarify the semisolid temperature range. The microstructure of the hot-rolled bar obtained at the semisolid temperature is the globular structure similar to those of aluminum and magnesium alloys. Then, to obtain a better understanding of the semisolid deformation behavior of the material, extrusion tests are carried out at various billet temperatures and cooling conditions at the die exit. To prevent the temperature decrease of the billet, a graphite case and block surrounding the billet acted as an insulator in the extrusion tests. The mechanical properties and the microstructure of the extruded products are evaluated and discussed, i.e., the extrusion force in the semisolid state is less than half that of the hot extrusion. The distribution of chemical components, such as carbon, is measured in the radial direction of the cross section of the products. The room-temperature hardness of the as-extruded products shows a specific distribution from the surface to the center. The hardness at the center is approximately two times greater than that at the surface.