Tensile Deformation Mechanisms Research Articles

Study on high temperature tensile constitutive behavior and deformation mechanism of Ti-47.5Al-2.5 V-1.0Cr-0.2Zr alloy

The high temperature tensile test of Ti-47.5Al-2.5 V-1.0Cr-0.2Zr alloy was carried out by electronic universal testing machine under the condition of 750–900 °C/10−5–10−3 s−1. The hot tensile stress-strain curves were analyzed, and the constitutive model under hot tensile conditions was established. The microstructure transformation rule and deformation mechanism during tensile process were determined. The results show that the hot tensile curve is longer in the steady-state flow stage corresponding to lower strain rate and higher tensile temperature, the true stress declines and the elongation at break increases. The constitutive equation was established based on the tensile curve data, and the corresponding thermal activation energy was 310.3 kJ/mol. As the rise of tensile temperature and the decline of strain rate, the proportion about cross-layer fracture in the tensile fracture morphology decreases, the number of dimples increases, more lamellar structures change into recrystallized structures, and the softening effect of the alloy is more obvious. The dislocation deformation mechanism mainly includes the existence of dislocation slip and climb, dislocation intersection and dislocation ring or dislocation network formation. Twinning deformation is also another important mechanism of high temperature tensile deformation of TiAl alloy. Twins are formed in parallel with each other, so that the deformation can be further carried out. The dislocations and twins in the deformed microstructure will provide nucleation conditions for recrystallized grains. The dynamic recrystallization(DRX) grains are preferentially formed around the grain boundary and the vicinity of dislocation and twin is also preferred nucleation site for DRX. The DRX behavior is the main softening mechanism, and DRX size and volume fraction corresponding to lower tensile rate and higher tensile temperature are larger.

Investigation of tensile deformation behavior of a TWIP/TRIP metastable β titanium alloy at typical temperature part Ⅰ: Room temperature

The tensile behavior and deformation mechanism of Ti-10Mo alloy at room temperature (298 K) were investigated. The results show that the alloy has an ultimate tensile strength (UTS) of 744 MPa and a high yield strength (YS) of 662 MPa, as well as an excellent elongation (El) after fracture of 38 %, outperforming Ti-15Mo alloy under the same conditions. The superior strength and plasticity of Ti-10Mo alloy at 298 K are attributed to the activation of both {332}〈113> twinning and SIM α“ during deformation. The sequence of different deformation mechanisms is as follows: in the initial stage of deformation, dislocation slip can be extensively activated and continues to occur during subsequent deformation; in the middle stage of deformation, primary and secondary {332}〈113〉 twinning and SIM α” are activated simultaneously, resulting in a continuous increase in work hardening rate; in the later stage of deformation, the alloy can further deform through {1 1 1}α“ twinning. The higher YS may be due to the optimal quantity and size of athermal ω phase in Ti-10Mo alloy, which increases the YS without significantly affecting plasticity. Meanwhile, Quenching vacancies can also increase the YS of the alloy. The three stages of the work hardening rate curve correspond to the activation of the dislocation slip mechanism, the activation of the {332}〈113〉 twinning and SIM α” and the stop of the {332}〈113〉 twinning and SIM α“.

The tensile behaviors of Ag-Cu alloys with different Cu contents: Molecular dynamics simulations study

The Ag-Cu alloys have received attention due to their excellent electrical and mechanical properties. However, the analytical research on why the mechanical properties of the Ag-Cu alloys increase after a small amount of Cu atoms are added is still lacked. In this work, the classical molecular dynamics (MD) simulations method was used to establish the Ag-Cu alloy models with different Cu contents. The tensile deformation mechanism of Ag-Cu alloy at room temperature was revealed from the atomic scale through the analysis of the stress-strain behavior and the evolution of dislocations. During the simulations, the embedded atom method (EAM) potential was used to describe the interaction between Ag atom and Cu atom. The uniaxial tensile deformation and nanostructure evolution of Ag-3 at.% Cu, Ag-6 at.% Cu and Ag-10 at.% Cu alloy models at the temperature of 300 K and the strain rate of 0.02 Å/ps were studied in detail. Results show that the internal stress was generated due to the large lattice mismatch among Ag atom, Cu cluster and the grain boundary. It results in the formation of dislocation and the negative initial stress at the beginning stage of Ag-Cu alloy models under tension. The dislocation firstly nucleates at the grain boundary and the growth rate of dislocation is slow before the crack propagation, and the complex dislocation reactions also exist. With the increase of Cu content, the tensile strengths of Ag-Cu alloys also increase. Cracks mainly form at the intersection of multiple grains, and the fracture mode changes from the intergranular fracture to the intergranular fracture and transgranular fracture after the unstable propagation of cracks. Meanwhile, a plenty of Cu atoms are distributed in the form of clusters in Ag matrix. They hinder the slip of dislocation and slow the relative sliding between atomic layers, and thus finally improves the deformation resistance to the plastic deformation of Ag-Cu alloy. The study on the tensile deformation behavior of Ag-Cu alloy at room temperature has certain guiding significance for the practical production and application of the design of Ag-Cu alloy.

The Evolution of Tensile Mechanical Properties and Deformation Mechanism of GH4720Li Nickel-Based Alloy with Temperature

The Evolution of Tensile Mechanical Properties and Deformation Mechanism of GH4720Li Nickel-Based Alloy with Temperature

Temperature-dependent deformation behavior of Hastelloy X Ni-based superalloy fabricated via laser powder bed fusion

Understanding the deformation behavior of additive manufacturing components across a wide spectrum of operating temperatures is crucial from an application standpoint. This study investigated the tensile deformation behavior of Hastelloy X (HX), fabricated via laser powder bed fusion (LPBF), over a temperature range of −50 °C–900 °C through uniaxial tensile tests. The focus was on the temperature-dependent tensile properties and deformation mechanisms of HX in a fully heat-treated condition, involving initial hot isostatic pressing followed by solution treatment. The results indicate that as the temperature increases, the ultimate tensile strength decreases sharply from approximately 790 MPa at −50 °C to 610 MPa at 200 °C, then gradually declines to 530 MPa at 600 °C, and finally drops to 230 MPa at 900 °C. Meanwhile, the yield strength falls rapidly from 345 MPa at −50 °C to 230 MPa at 200 °C, then slowly reduces to 170 MPa at 600 °C, stabilizing up to 900 °C. Electron back scattered diffraction analysis revealed that with rising temperature, the predominant plastic deformation mechanism transitions from deformation twinning to slip bands and eventually to dynamic recrystallization. Remarkably, the strain hardening capacity increases with rising temperature below 600 °C, attributed to the beneficial effects of deformation twins and subsequent slip bands. Furthermore, dynamic strain aging takes place between 300 °C and 600 °C, slightly limiting the improvement of plasticity within this intermediate temperature range. Understanding these temperature-dependent deformation mechanisms in heat-treated LPBF HX would provide valuable insights into its performance over a wide range of service temperatures.

Research on the ultra-low temperature tensile deformation mechanism of Al-Mg-Si alloys in different heat treatment states

The susceptibility of Al-Mg-Si alloy to cracking during room temperature large plastic deformation poses a significant obstacle to its widespread application. Cryogenic temperature forming of aluminum alloys has emerged as a prominent research topic. However, the precise mechanisms underlying the enhancement of aluminum alloy plasticity in different states remain elusive. In order to elucidate this matter, a series of uniaxial tensile experiments were conducted on Al-Mg-Si alloy featuring diverse initial states, under varying temperature conditions. The results show that when the deformation temperature is reduced from 25℃ to −196℃, the tensile strength and elongation of the wrought material are increased by 48 MPa and 5.42 %, and the tensile strength and elongation of the annealed material are increased by 118 MPa and 5.65 %. In contrast, while the T4 state sample exhibited a significant improvement in tensile strength (103 MPa), no substantial enhancement in elongation was observed. This disparity can be primarily attributed to the absence of second-phase precipitation in the as-forged and annealed states. As the temperature decreased, the critical shear stress increased, resulting in increased resistance to deformation. Consequently, an increased degree of lattice rotation and activation of dislocations in various slip systems ensued, thereby improving the deformation uniformity. The formation of initial microvoids predominantly occurred close to grain boundaries. Therefore, compared with room temperature deformation, low temperature deformation caused by the accumulation of dislocations and hole sprouting concentrated at a single location was less likely. As a result, the dislocation distribution was more uniform and fracture was less likely to occur. Conversely, in the T4 state, the aging process resulted in the precipitation of a substantial amount of the soluble second phase (Mg5Si6). Consequently, microvoid nucleation transpired at the phase boundaries, leading to an elevated tensile strength. However, because of the increased dislocation hindrance when the deformation temperature was lowered, no significant enhancement in plasticity was observed.

Hot extrusion, tensile deformation behavior and deformation mechanism analysis of a wrought superalloy with a high γ′ phase volume fraction of 64 %

A hundred kilograms of GH4975 extrusion bar, featuring fine equiaxed grains, were successfully fabricated using electron beam smelting layer solidification(EBSL) and hot extrusion techniques. Subsequent analysis focused on the microstructure and tensile properties of the extruded bar. The study also delved into the influence of temperature on tensile deformation behavior and mechanisms of the alloy after standard heat treatment(SHT). The results revealed uniformity in precipitated phase size and morphology across the extruded bar, with grain size being the largest at the center and smallest at the edge. Tensile tests conducted at 20 °C and 650 °C show an obvious work hardening phenomenon, and the deformation mechanism is dominated by APB coupled dislocation pairs shearing. With the increase of deformation temperature, the work-hardening phenomenon gradually weakens, and SFs emerge as the primary deformation mechanism at 750 °C. As the deformation temperature further rises, cross slip, Orowan bypass and dislocation climbing gradually dominate. The fracture mode changes from brittle fracture to ductile and brittle mixed fracture, and ultimately to brittle fracture. Compared with the traditional preparation method, the hundred kilograms of GH4975 extrusion bar prepared by this technology still show better mechanical properties.

Atomistic study of selenium doping effects on the mechanical properties of zinc-blende and wurtzite CdTe nanowires

CdSexTe1–x semiconductor materials, having potential to be used to design dependable and reproducible nanowire devices, require an extensive study of their mechanical behaviors. The uniaxial tensile deformation mechanism of CdSexTe1–x nanowires (NWs) with different Se dopant concentration are yet to be explored. By integrating theoretical analysis with computational simulation, this research demonstrated that Se doping in CdTe NWs influences the mechanical response and failure modes. Ultimate tensile strength (UTS) and elastic modulus (EM) were studied for both zinc-blende (ZB) and wurtzite (WZ) structures with different crystal orientations. The findings revealed that these mechanical properties increase linearly with increasing Se concentration in all cases. In addition, the WZ structures exhibited similar mechanical properties under both zigzag and armchair loadings, unlike the ZB structures, which exhibited a strong dependence on the crystal orientation. The [111]-oriented ZB structures showed the highest EM and UTS whereas [100]-oriented ZB structures showed lowest EM and UTS. The failure mechanism was explored for CdSe50Te50 to underscore the influence of the dopant on the NWs failure for tensile loading. In both the cases of WZ structure, the failure planes were perpendicular to the loading direction. Furthermore, the failure plane varied with the Se content in ZB CdSexTe1–x. Atomic coordination and bond length affected by doping defined the alterations of mechanical properties and the preferred modes of failure. The significance of the interaction between doping elements and nanowire structures offers insights that unite material science and mechanics, contributing to the scientific understanding of solid materials’ behavior.

The influences of microstructural length scale on the tensile properties and deformation mechanisms of Sn-3.0Ag-0.5Cu solder alloys

Optimizing microstructures remains critical for improving the reliability of Pb-free solder joints, especially in applications with high failure risks. The mechanical properties of Sn-3.0Ag-0.5Cu (SAC305) solder alloys is intricately linked to the length scale of the initial microstructure. This paper investigates the effects of microstructure refinement on uniaxial tensile properties, nanomechanical response, plastic deformation, and fracture using directional solidification techniques. The findings demonstrate that controlling the microstructure can effectively enhance mechanical properties, dynamic recrystallization, and intragranular deformation in SAC305 alloys. Furthermore, the study explores heterogeneous plastic deformation and the interaction between eutectic intermetallics and β-Sn. These results offer valuable insights for optimizing microstructures to achieve superior solder joint performance.

Microdeformation and strengthening mechanism of 3D printed TC4/TC11 gradient titanium alloy subjected to tensile loading

3D printing of heterogeneous alloys holds promising application potentials in industry, especially in the field of aerospace. However, the relationship between the microstructure and mechanical properties of heterogeneous gradient titanium alloys produced by this technique, especially the micromechanical properties and mechanisms within the gradient zones, remains largely unexplored. In this study, we investigated the tensile micromechanical properties and deformation mechanism of 3D printed TC4/TC11 titanium alloy using the digital image correlation method in combination with scanning electron microscopy. The results show that this heterogeneous gradient titanium alloy possesses superior tensile properties. Furthermore, we elucidated the influence of microstructure and grain size on the alloy’s mechanical properties. Notably, an increased presence of secondary α phases and refined grain size were found to reduce the likelihood of microcrack initiation and propagation. Interestingly, all samples fractured on the TC4 side, with the microcracks predominantly extending at a 45° angle to the tensile direction. This observation underscores the necessity for optimizing the fabrication process of the TC4 alloy. Additionally, the strengthening mechanism of the gradient-bonded region of the alloy was also explored. The heterogeneous deformation-induced strengthening was identified as a key factor enhancing the strength of the dual alloyed zone. Collectively, this study provides valuable insights for optimizing the 3D printing process of heterogeneous gradient titanium alloys. It also lays a solid foundation for future investigation in this burgeoning field.

Atomistic simulations of tensile properties and deformation mechanisms in a gradient nanostructured Al0.3CrFeCoNi high-entropy alloy

Atomistic simulations of tensile properties and deformation mechanisms in a gradient nanostructured Al0.3CrFeCoNi high-entropy alloy

A single-phase Nb25Ti35V5Zr35 refractory high-entropy alloy with excellent strength-ductility synergy

Refractory high entropy alloys (RHEAs) are promising candidates for high-temperature structural materials due to their excellent high-temperature performance. However, the room-temperature brittleness of most alloys results in poor plastic formability, thereby limiting their engineering applications. In this study, Nb25Ti35V5Zr35 alloy with cold-rollability was developed, and its phase stability, tensile mechanical properties, elastic properties, strengthening mechanism, and deformation mechanism were investigated by combining experiments, CALPHAD, DFT and molecular statics (MS) methods. The results demonstrate that Nb25Ti35V5Zr35 alloy possesses good phase stability, with both the as-cast and annealed states maintaining a single-phase BCC structure without undergoing phase transformation. The tensile yield strength of the alloy reaches its peak at 1152 MPa in the cold-rolled condition, while its annealed state exhibits an optimal balance of strength and plasticity, with a yield strength of 836 MPa and an elongation of 22.45 %, respectively. Solid solution strengthening is the primary source of its high strength, with V and Zr playing key roles in this strengthening mechanism. Dislocation slip plays a dominant role in plastic deformation. Additionally, compared to traditional BCC alloys, the significance of edge dislocations in the deformation process is notably enhanced, with the {112} plane serving as the preferred slip plane for dislocations. DFT results indicate that the alloy exhibits significant anisotropy in both Young's modulus and shear modulus. This work contributes to understanding the material properties of the Nb25Ti35V5Zr35 alloy and provides a reference for the design of new ductile RHEAs.

Transitioning of deformation mode in bicrystalline Al-Mg alloy with Σ3 [1 1 1] 60° {11 8 5} faceted grain boundary

In this letter, the authors have elucidated the effect of alloying biocompatible and lighter magnesium (Mg) solute atoms in a bicrystalline aluminium (Al) solvent incorporated with a faceted coherent-incoherent grain boundary (GB) to analyze the tensile deformation mechanisms. Cryogenic temperature and high strain rate conditions were imposed through molecular dynamics simulations to report the detrimental effect of Mg addition on the tensile strength of Al-Mg alloys. Evidence of transitioning in deformation modes for pure Al and Al-Mg alloys was seen. On elaborating, for pure Al, GBs acted as the dislocation nucleation site; whereas for Al-Mg alloy, it was both the GBs and grains. It was observed that stacking faults (SFs) originated from GBs and propagated toward grains in Al. In contrast, in Al-Mg alloys, SFs were generated simultaneously from both GBs and grains. This simultaneous nucleation of dislocations and SFs from both GBs and grains renders bicrystalline alloys lower the elastic limit than pure metal. Conversely, beyond this elastic limit, the alloys exhibit higher flow stress than the pure metal due to the Mg-dislocation interactions. These findings offer valuable insights for tailoring the mechanical properties of Al-Mg alloys to meet aerospace, automotive and marine engineering-related application requirements.

Effect of primary α phase fraction on deformation mechanism of Ti-1023 alloy at room temperature

The fraction and morphology of α phase have important effects on the mechanical properties and deformation mechanism of Ti-1023 alloy. Here, the tensile stress-strain curves and deformation mechanisms with the fraction of α phase are discussed in detail. As α phase fraction decreases from 67.5 % to 12.6 %, there is a negative correlation coefficient between the yield strength and α phase volume fraction of Ti-1023 alloy, and its fitting equation is obtained. When the fraction of α phase is decreased to 12.6 %, the elongation and ultimate tensile strength of the alloy are 31.09 % and 845.52 MPa, as well as a transition from single to double yielding phenomenon, which is caused by stress-induced martensitic transformation (SIMT). When the fraction of α phase is high, the deformation mechanism is dominated by dislocation slip and mechanical twinning of the α phase. When the fraction of α phase is low, the deformation mechanism is dominated by mechanical twinning of the β matrix and stress-induced martensitic transformation (SIMT). The relationship between α phase fraction and deformation mechanism and mechanical properties of Ti-1023 in α+β dual phase region is studied, which provides a template to guide the development of comprehensive mechanical properties of metastable β titanium alloy in α+β dual phase region.

Deformation Mechanisms Dominated by Decomposition of an Interfacial Misfit Dislocation Network in Ni/Ni3Al Multilayer Structures.

Ni/Ni3Al heterogeneous multilayer structures are widely used in aerospace manufacturing because of their unique coherent interfaces and excellent mechanical properties. Revealing the deformation mechanisms of interfacial structures is of great significance for microstructural design and their engineering applications. Thus, this work aims to establish the connection between the evolution of an interfacial misfit dislocation (IMD) network and tensile deformation mechanisms of Ni/Ni3Al multilayer structures. It is shown that the decomposition of IMD networks dominates the deformation of Ni/Ni3Al multilayer structures, which exhibits distinct effects on crystallographic orientation and layer thickness. Specifically, the Ni/Ni3Al (100) multilayer structure achieves its maximum yield strength of 5.28 GPa at the layer thickness of 3.19 nm. As a comparison, the (110) case has a maximum yield strength of 4.35 GPa as the layer thickness is 3.01 nm. However, the yield strength of the (111) one seems irrelevant to layer thickness, which fluctuates between 10.89 and 11.81 GPa. These findings can provide new insights into a deep understanding of the evolution and deformation of the IMD network of Ni/Ni3Al multilayer structures.

Effect of Ta on Tensile Behavior and Deformation Mechanism of a Nickel-Based Single Crystal Superalloy

Effect of Ta on Tensile Behavior and Deformation Mechanism of a Nickel-Based Single Crystal Superalloy

Plastic deformation mechanism of TA1 pure titanium plate using SEM-EBSD in-situ tensile testing

As the core component of proton exchange membrane fuel cell (PEMFC), pure titanium bipolar plate has been faced with cracking and thinning problems in the forming process. It is considered that the stamping and tensile deformation of the bipolar plate have similar stress states. In this paper, the plastic deformation mechanism of TA1 pure titanium plate is analyzed from the aspects of twin, texture evolution and dislocation slip by in-situ tensile combined with SEM/EBSD. During tensile deformation, a large number of dislocation slips occur inside α grain, and obvious slip traces are produced on the surface of the sample. Within grains with different crystallographic orientations, the degree and direction of the trace are different, which leads to the increased disharmony between grains. Especially in the triple junction of grain boundary, soft/hard orientation grain junction and other deformation disharmony locations are easy to crack. The tensile deformation causes obvious changes in the texture, and the initial strong bimodal texture becomes weak bimodal texture. This phenomenon is explained by intragranular misorientation, crystal rotation and twins. The main mechanism of tensile deformation of titanium plate is slip and twinning. A large number of {11–22}<11-2-3> compression twins are formed due to most c-axis bearing compressive stress. The types of initiating slip systems are different in different stages. The cylindrical slip system is preferentially activated and occupies a dominant position before yielding, which is conducive to the plastic forming of the plate. After yielding, the start-up ratio of the pyramidal slip system is increased due to the deflection of the observed surface of sample during tensile process, which improves the deformation resistance of the thin plate.

Delayed recrystallization behavior and deformation mechanism of IN738LC alloy prepared by laser powder bed fusion

The design and development of heat treatment regimes adapted to the laser powder bed fusion technology for specific service conditions have become a hot topic of research in the field of additive manufacturing. This paper systematically studies the microstructure changes of the L-PBFed IN738LC alloy, solution heat treated at 1250 °C for various durations (1 h, 3 h, 5 h) and then aged at 850 °C for 24 h. The delayed recrystallization behavior was revealed, and the selective precipitation pattern of the M23C6 carbide on different types of grain boundaries was discussed. Additionally, the tensile deformation mechanism of the alloy before and after heat treatment is clarified. The results indicate that grain boundary migration and transformation are impeded under 1250 °C/1 h conditions due to carbide particle pinning and solute atom segregation during the initial stage of solution treatment, which accounts for the delayed recrystallization behavior, and the microstructure is mainly undergoing recovery. At 1250 °C/5 h, M23C6 carbides selectively precipitate at twin boundaries, accompanied by recrystallization. The samples treated at 1250 °C/1 h exhibit the highest mechanical property (σYS=1305 ± 21 MPa, σUTS=1462 ± 11 MPa, εEL=5.4 ± 0.7 %) owing to the precipitation of γ′ phase and the presence of sub-grain boundaries. The deformation mechanism shows that the as-built samples mainly experience planar dislocations slipping, while the heat-treated samples undergo stacking faults shearing and anti-phase boundary shearing. The dominant mechanism among these is anti-phase boundary shearing.

Unveiling the Stacking Fault-Driven Phase Transition Delaying Cryogenic Fracture in Fe-Co-Cr-Ni-Mo-C-Based Medium-Entropy Alloy.

In this work, the tensile deformation mechanisms of the Fe55Co17.5Cr12.5Ni10Mo5-xCx-based medium-entropy alloy at room temperature (R.T.), 77 K, and 4.2 K are studied. The formation of micro-defects and martensitic transformation to delay the cryogenic fracture are observed. The results show that FeCoCrNiMo5-xCx-based alloys exhibit outstanding mechanical properties under cryogenic conditions. Under an R.T. condition, the primary contributing mechanism of strain hardening is twinning-induced plasticity (TWIP), whereas at 77 K and 4.2 K, the activation of martensitic transformation-induced plasticity (TRIP) becomes the main strengthening mechanism during cryogenic tensile deformation. Additionally, the carbide precipitation along with increased dislocation density can significantly improve yield and tensile strength. Furthermore, the marked reduction in stacking fault energy (SFE) at cryogenic temperatures can promote mechanisms such as twinning and martensitic transformations, which are pivotal for enhancing ductility under extreme conditions. The Mo4C1 alloy obtains the optimal strength-ductility combination at cryogenic-to-room temperatures. The tensile strength and elongation of the Mo4C1 alloy are 776 MPa and 50.5% at R.T., 1418 MPa and 71.2% in liquid nitrogen 77 K, 1670 MPa and 80.0% in liquid helium 4.2 K, respectively.

Study on the tensile properties and deformation mechanism of high-temperature resistant nitrogen-containing nickel-based welding material deposited metal

This article uses a new type of nitrogen-containing nickel-based flux cored welding wire as the experimental material to study the tensile properties and deformation mechanism of the deposited metal from room temperature to 900 °C. The results show that the tensile strength gradually decreases with the temperature. The plasticity gradually increases, but the lowest value appears at 700 °C, which is the phenomenon of intermediate temperature brittleness. M23C6 carbides begin to decompose at 700 °C. More carbonitrides are precipitated within the crystal with temperature. In the low-temperature zone (T ≤ 600 °C), the main deformation mechanism is the unit dislocation a/2<110> cutting precipitation phase. In the medium-temperature zone (600 °C < T ≤ 750 °C), initiation of Orowan bypass mechanism for dislocations. In the high-temperature zone (800 °C ≤ T ≤ 900 °C), the slip and climbing mechanism of dislocation is the main deformation mechanism.