Evolution of Microstructure During Tensile Deformation of TB5 Titanium Alloy

AbstractEvolution of microstructure of TB5 titanium alloy was studied during tensile deformation. It was found that the slip bands increased and the angle of slip bands decreased when deformation displacement increased. Besides, during elastic deformation, only the grain shape changed; while during plastic deformation, the single slip band appeared initially. With increasing in deformation displacement, grains rotated and multi slip bands appeared. At the same time, geometrical hardening appeared and cross slips appeared finally

In-Situ Synchrotron HEXRD Study on the Micro-Stress Evolution Behavior of a Superalloy during Room-Temperature Compression

The residual stress generated during heat treatment of nickel-base superalloys will affect their service performance and introduce primary cracks. In a component with high residual stress, a tiny amount of plastic deformation at room temperature can release the stress to a certain extent. However, the stress-releasing mechanism is still unclear. In the present study, the micro-mechanical behavior of the FGH96 nickel-base superalloy during room temperature compression was studied using in situ synchrotron radiation high-energy X-ray diffraction. The in situ evolution of the lattice strain was observed during deformation. The stress distribution mechanism of grains and phases with different orientations was clarified. The results show that at the elastic deformation stage, the (200) lattice plane of γ′ phase bears more stress after the stress reaches 900 MPa. When the stress exceeds 1160 MPa, the load is redistributed to the grains with their crystal directions aligned with the loading direction. After yielding, the γ′ phase still bears the main stress

Effects of Strength and Distribution of SiC on the Mechanical Properties of SiCp/Al Composites

In this paper, considering the strength and geometric discrete distribution characteristics of composite reinforcement, by introducing the discrete distribution function of reinforcement, the secondary development of ABAQUS is realized by using the Python language, the parametric automatic generation method of representative volume elements of particle-reinforced composites is established, and the tensile properties of silicon carbide particle-reinforced aluminum matrix composites are analyzed. The effects of particle strength, particle volume fraction, and particle random distribution on the mechanical properties of SiCp/Al composites are studied. The results show that the random distribution of particles and the change in particle strength have no obvious influence on the stress–strain relationship before the beginning of material damage, but have a great influence on the damage stage, maximum strength, and corresponding failure strain. With the increase in particle volume fraction, the damage intensity of the model increases, and the random distribution of particles has a great influence on the model with a large particle volume fraction. The results can provide a reference for the design, preparation, and characterization of particle-reinforced metal matrix composites

In Situ Synchrotron HEXRD Study on the Deformation Mechanism of a Nickel-Based Superalloy during Medium-Temperature Compression

The γ′ phase has an important influence on the deformation mechanism of solid-solution strengthening nickel-based superalloys. The microfracture behavior of the alloy depends on the mechanism of stress and strain partitioning between the γ and γ′ phase under load. In this study, the in situ synchrotron radiation high-energy X-ray diffraction technique was used to observe the deformation process of the FGH96 nickel-based superalloy with a γ′ volume fraction of about 40% at 650 °C and 750 °C. The results show that the (111) reflection had the greatest stiffness and showed plastic deformation first; while the (200) reflection bore a larger load. The γ phase yielded first and began to deform plastically; then the load was transferred to the γ′ phase. At 650 °C, the plastic deformation of the γ′ phase was relatively higher; while at 750 °C, the γ′ particle basically maintained elastic deformation with a tiny amount of plastic deformation

Dynamic behavior and microstructural evolution of TiAl alloys tailored via phase and grain size

As a kind of promising aerospace material, TiAl alloys need to withstand extreme conditions such as high-rate impact loads and high temperatures. The mechanism on the failure and fracture of TiAl alloys under extreme conditions is related with the microstructure, including phase and grain size. In the present research, two kinds of TiAl alloys tailored with different microstructures, near lamellar (NL) and near gamma (NG), were fabricated by thermo-mechanical treatment. Microstructural characterization was analyzed by XRD and EBSD. The dynamic behavior of the TiAl alloys under different temperatures ranging from 293 K–873 K was investigated by a split Hopkinson pressure bar. The strain rate sensitivity and temperature sensitivity was analyzed. The microstructural evolution was concerned to understand the failure mechanism of the two kinds of the TiAl alloys. The NG-TiAl had the homogeneous deformation with synergy effect between homogeneous equiaxed grain and lamellar structure, and no failure occurred in NG-TiAl. However, the NL-TiAl showed heterogeneous deformation with both “orange peel effect” and cracks, which was attributed to large equiaxed grain and brittle γ-lamellae with similar orientation. Further, the cracks were easily nucleated and propagated from the interface between γ-lamellae structures, especially in the γ-lamellae structures parallel with the loading direction. Finally, the modified Johnson–Cook constitutive model was proposed to describe the deformation behavior, in which both strain rate hardening and temperature softening terms were expressed as a function of strain and strain rate