Deformation Of Alloy Research Articles

Ti-Zr-V-Nb-Al BCC high-entropy alloy with outstanding uniform ductility achieved by grain refinement

The lack of sufficient uniform deformation ability of body-centered cubic (BCC) high-entropy alloys (HEAs) is the obstacle to their applications as structural materials. Here we present a grain refinement strategy to achieve excellent uniform ductility of a BCC non-equal atomic ratio Ti-Zr-V-Nb-Al (TZ) alloy. The uniform elongation and yield strength of the fine-grained TZ alloy with a grain size of 15 µm are as high as ~12% and 840 MPa, respectively. The outstanding uniform deformability of the fine-grained TZ alloys is due to the frequent cross-slip events and abundant dislocation tangles. Grain refinement can increase the probability of dislocation entanglement, thereby promoting a rise in the work-hardening rate. The good plasticity and high work-hardening rate can improve the uniform deformation ability. Our results will give new insights into enhancing uniform ductility while maintaining high strength in the BCC HEAs.

Surface Integrity and Machining Mechanism of Al 7050 Induced by Multi-Physical Field Coupling in High-Speed Machining

Improving the surface quality and controlling the microstructure evolution of difficult-to-cut materials are always challenges in high-speed machining (HSM). In this paper, surface topography, defects and roughness are assessed to characterize the surface features of 7050 aluminum alloy (Al 7050) under HSM conditions characterized by high temperature, strain and strain rate. Based on multi-physical field coupling, the mechanism of microstructure evolution of Al 7050 is investigated in HSM. The results indicate that the surface morphology and roughness of Al7050 during HSM are optimal at fz = 0.025 mm/z, and the formation of surface defects (adherent chips, cavities, microcracks, material compression and tearing) in HSM is mainly affected by thermo-mechanical coupling. Significant differences are observed in the microstructure of different machined subsurfaces by electron backscatter diffraction (EBSD) technology, and high cutting speeds and high feed rates contributed to recrystallization. The crystallographic texture types on machined subsurface are mainly {110}<112> Brass texture, {001}<100> Cube texture, {123}<634> S texture and {124}<112> R texture, and the crystallographic texture type and intensity are significantly affected by multi-physical field coupling. The elastic–plastic deformation and microstructural evolution of Al7050 alloy during the HSM process are mainly influenced by the coupling effects of multiple physical fields (stress–strain field and thermo-mechanical coupling field). This study reveals the internal mechanism of multi-physical field coupling in HSM and provides valuable enlightenment for the control of microstructure evolution of difficult-to-cut materials in HSM.

Construction and application of a physically-based constitutive model for superplastic deformation of near-α TNW700 titanium alloy

Construction and application of a physically-based constitutive model for superplastic deformation of near-α TNW700 titanium alloy

Deformation mechanism and microstructure evolution of newly developed Ti-42.5Al-4Nb-0.5Mo-0.1B-(C, W, Y) alloy

A novel Ti-42.5Al-0.5Mo-0.1B-0.2W-0.25C-0.05Y alloy with a nearly lamellar structure was explored to better understand the deformation behavior and microstructure evolution during hot compression test at a high strain rate of 10s-1. Cylindrical samples were compressed in the temperature range of 1373K to 1523K, with the true strain reaching 69%. The results show that the crystal structure and phase transformation have an influence on the deformation mechanisms. Regarding the Tα2→α transformation within the deformation temperature range of 1373K - 1473K, the nucleation and growth of dynamically recrystallized (DRXed) γ and α grains can alternate in dominating the hot deformation of the present alloy. When the deformation temperature is 1523K, the softening mechanism mainly is the dynamic recovery (DRV) of the α phase. Moreover, the deformation temperature also has a significant effect on phase fractions and the critical values of dynamic recrystallization. Specifically, as the temperature rises, the proportion of the α phase increases, the proportion of the γ phase decreases sharply, the content of the β phase remains stable, and the critical values of dynamic recrystallization decrease. Additionally, fine equiaxed α2 grains with an average size of 8 μm were obtained at 1523K and 10s-1, which provided a reference for obtaining a fine near-lamellar or full-lamellar microstructure in TiAl alloys.

The effect of strain rate on macrozones of the α+β phase region during thermal deformation in near-α titanium alloys

The effect of strain rate on macrozones of the α+β phase region during thermal deformation in near-α titanium alloys

Microstructure evolution and dynamic recrystallization mechanism of tantalum-tungsten alloys under hot compression

Ta-W alloys exhibit outstanding comprehensive properties at high temperatures, allowing them to have great application prospects in the high-temperature field. High-temperature compression tests (1573~1873 K) were conducted to evaluate the high-temperature mechanical properties of Ta-12W alloy, and the strain-compensated Arrhenius-Type model and hot processing map were developed to predict the optimal processing window. The electron backscatter diffraction, Transmission electron microscope, and DEFORM-3D software were performed to investigate the microstructure evolution and distributions of strain. The results demonstrated that the flow stress of Ta-12W alloy presented apparent negative temperature sensitivity and positive strain rate sensitivity. Based on the thermal processing diagrams and EBSD analysis, the results show that the low deformation temperature and high strain rate introduce stress concentration and deformation instability in the Ta-12W alloy. The optimized processing temperature and strain rate are at 1800 ~1873 K/0.001 s-1~0.05 s-1, and the microstructure at 1873 K/0.001 s-1 is more uniform and exhibits a low residual stress level. As the temperature increases, dynamic recovery and dynamic recrystallization cause significant softening effects, and continuous dynamic recrystallization dominates the high-temperature deformation behavior. Moreover, multiple continuous dynamic recrystallizations occur simultaneously, including sub-grain nucleation inside large grains, sub-grain nucleation at grain boundaries, and grain fragmentation accompanied by grain rotation. This study revealed the mechanisms of microstructural evolution during hot deformation of Ta-12W alloy, providing important guidance for optimizing the thermomechanical processing parameters.

Effects of rapid infrared radiation heating on the warping deformation and mechanical properties of selective laser melted Co-Cr dental alloy.

Infrared radiation heating (IRH) technology has been innovatively applied to the annealing of selective laser melted (SLM) cobalt chromium (Co-Cr) frameworks. However, previous studies have not reported the effects of IRH on the warping deformation and mechanical properties of these frameworks. The purpose of this in vitro study was to investigate the effects of IRH on the warping deformation and mechanical properties of dental SLM Co-Cr alloy and to evaluate its potential applications in dental restorations. Two types of specimens, bone-shaped tensile specimens and warping deformation specimens (cantilever beam structures), were fabricated by SLM, followed by annealing using IRH and general furnace heating (GFH). The specimens were divided into 4 groups (n=6) based on the applied heat treatment method and build direction (IRH-XY; IRH-Z; GFH-XY; GFH-Z). The cantilever beam support structure of the warping deformation specimen was cut using wire cutting, and the warping deformation was measured using a digital image correlation optical extensometer. Tensile tests were used to evaluate mechanical properties, with the fracture characteristics being observed using a scanning electron microscope (SEM). A micro-Vickers hardness tester was used to measure the microhardness. The microstructures were analyzed using a metallographic microscope. All data were analyzed using a 1-way ANOVA and the Tukey Honestly Significant Difference test (α=.05). The surfaces of the SLM Co-Cr warping deformation specimens treated with IRH showed slight oxidation, while those treated with GFH exhibited a dark black appearance. No significant difference was found in deformation between the IRH group (0.412 ±0.039 mm) and the GFH group (0.379 ±0.070 mm) (P>.05). The elongation of the longitudinally built specimens was significantly higher than that of their transversely built counterparts (P<.05), while the yield strength showed an opposite trend. The longitudinally built specimens demonstrated ductile fracture characteristics, while the transversely built specimens displayed quasi-cleavage fractures. The specimens treated with IRH exhibited comparable tensile strength and microhardness with the GFH-treated specimens, with no statistically significant differences (P>.05). IRH treatment resulted in finer grains in the SLM Co-Cr alloy. Many fine second-phase particles precipitated from the matrix in the longitudinally built specimens, while few were observed in the transversely built specimens. The SLM Co-Cr specimens treated with IRH achieved comparable warping deformation and mechanical properties with those of the GFH-treated specimens. The IRH technology holds great potential for application to dental restorations.

Direct determination of diffusion flux in alloys via spatial separation of flux

Despite the importance of atomic diffusion in controlling high temperature deformation, it remains difficult to generally determine diffusion flux through alloys. We present thermomechanical nanomolding, where a nanomold is filled by the alloy's diffusion flux under a stress gradient, to determine the flux diffusing through an alloy's microstructure. This flux is collected in the nanomold forming nanorods. Length and composition analyses of the formed nanorods allow us to determine rate and composition of the flux, and further allow estimation of the constituents’ diffusivities in this flux. We verify this technique on metals and simple alloys, and then reveal diffusive flux in general alloys. Notably, for alloys that can access a eutectic composition in their alloy system, the flux's composition is that of the eutectic, which can be very different from the alloy's nominal composition. Moreover, the flux's overall diffusivity is greatly enhanced. This, so far unknown, eutectic mechanism is present in the majority of multicomponent alloys. These insights into diffusion flux in alloys can be used to guide the development of alloys with particularly low diffusivity or particularly high diffusivity. More generally, the presented method provides a novel toolbox to reveal the rich underlying diffusion-controlled mechanisms of deformation of alloys in general.

Numerical study of a three-stage metal hydride hydrogen compressor considering alloy bed deformation

ABSTRACT Metal-hydride hydrogen compressors offer a promising alternative for compressing hydrogen to high pressures. Before conducting experimental investigations, an in-depth numerical analysis is essential for designing suitable reactors, optimizing operating parameters, and evaluating performance. This work presents a comprehensive numerical model for a three-stage MHC, focusing on higher delivery pressures exceeding 300 bar with an absorption pressure of 15 bar. The model uniquely incorporates alloy bed deformation, a factor previously overlooked. It is found that the selected alloys can compress 82 L of hydrogen up to 340 bar at 363 K in 5.4 hr, achieving a productivity of 15.2 L/h. A crucial observation revealed a maximum radial variation in bed permeability of 96.9%, highlighting the importance of considering bed deformation during the sorption process. Additionally, the bed exhibited a significant 206.7% variation in the reacted fraction from the center to the periphery. To optimize MHC performance while slightly compromising the weight ratio, the study recommends limiting reactor diameters to 20–30 mm. Furthermore, the analysis of source and sink temperatures showed that sink temperature has a more substantial impact on compression performance, providing valuable insights for optimizing operating conditions to enhance MHC efficiency.

Increasing the technological deformability of titanium alloy during rolling using electric current pulses

Increasing the technological deformability of titanium alloy during rolling using electric current pulses

On the Possibility of the Deformation of Mg and Alloys Without Preheating of Initial Billets: Understanding Their Corrosion Performance via Electrochemical Tests.

Due to limited slip systems activated at room temperature, the plastic deformation of Mg and its alloys without any preheating of initial billets is significantly limited. To overcome those issues, new methods of severe plastic deformation are discovered and developed. One such example is extrusion with an oscillating die, called KoBo. This method, due to the oscillations of reversible die located at the end of extruded, introduces material into the plastic flow, and thus, enables deformation without preheating of the initial billets of metals that are hard to deform. Such solution is important from an industrial point of view and may lead to serious savings and reduction in carbon dioxide emission to the atmosphere. Therefore, this paper focuses on the possibility of KoBo extrusion of hcp-structured Mg alloys with different chemical compositions and includes comparison of their corrosion resistance using short-term electrochemical tests. In order to have a broad view of the problem presented, we compared the electrochemical behavior of the following groups of Mg materials: pure Mg, Mg-Al-Zn, Mg-Li, and Mg-Y-RE. It was stated that the KoBo method performed at room temperature improves the corrosion resistance of pure Mg when compared to the initial billet and the alloys which belong to the Mg-Al-Zn, Mg-Li, and Mg-Y-RE series. The presented study shows that different corrosion trends are observed for traditionally deformed alloys, and they significantly vary from nascent developments, such as KoBo extrusion. Therefore, it is crucial to widely study those methods because it may be a path leading to long-lasting solution to the formability limitations of Mg-based metallic systems.

Mechanical behavior of supersonic fine particle bombardment single crystal γ-TiAl alloys based on atomistic simulation: effects of velocity and crystal plane

Abstract The crystal orientation significantly affects the plastic deformation and mechanical properties of γ-TiAl alloys. However, there are few studies on the mechanical behavior of supersonic fine particle bombardment (SFPB) of single-crystal γ-TiAl alloys impacted with different crystal planes and velocities at the nanoscale. And the characterization of the mechanical properties in the presence of dislocation defects after impact is lacked. Therefore, in this paper, molecular dynamics is used to simulate the impact response and post-impact mechanical response of SFPB single-crystal γ-TiAl alloy. The results show that: at a certain impact velocity, the different ways of inducing dislocation slip due to the number of slip system initiations under crystal anisotropy lead to a smaller depth of subsurface damage on the (001) crystallographic plane compared to the other crystallographic planes; moreover, the yield strength and Young’s modulus of the (111) and (1 1 ¯ 0) crystallographic planes are the largest after the impact, respectively. Under the same crystal plane, the subsurface damage depths of all crystal planes decrease with the increase of impact velocity; the yield strength of the (111) crystal plane of γ-TiAl alloy gradually increases, the yield strength of the (001) and (1 1 ¯ 0) crystal planes decreases, and the modulus of elasticity of the (001) and (111) crystal planes after impact is less sensitive to velocity. The angle between the two slip surfaces formed by the L-C dislocation during impact is 70.24°, while the angle between the two slip surfaces formed by the Hirth dislocation is 109.76°. This will provide atomic-scale deformation details of the plastic deformation and mechanical response of single-crystal γ-TiAl alloys bombarded by supersonic fine particles.

Oxidation Behavior and Creep Resistance of Cast MC-Strengthened CoNiFeMnCr HEAs at 1100 °C

The reinforcement of cast Cantor’s-type high-entropy alloys by MC carbides and their effect on the hot oxidation behavior were investigated. Three equimolar CoNiFeMnCr alloys without or with carbon and with either hafnium or tantalum were elaborated. Their as-cast microstructures were specified. Oxidation tests were carried out in air at 1100 °C. Flexural creep tests were performed at 1100 °C at 10 MPa. The carbide-free CoNiFeMnCr alloy was single-phased. The version with Hf and C added and the one with Ta and C added contained interdendritic eutectic script HfC and TaC carbides, respectively. After oxidation for 50 h at 1100 °C, all alloys were covered by a (Cr,Mn)2O3 scale with various proportions of Cr and Mn. HfO2 or CrTaO4 also formed. Oxidation resulted in a deep depletion in Cr and in Mn in the subsurface. Oxidation is much faster for the three alloys by comparison with chromia-forming alloys. Their bad oxidation behavior is obviously due to Mn and protection by coating is to be considered. The creep deformation of the carbide-free CoNiFeMnCr alloy was very fast. The creep resistance of the two versions reinforced by either HfC or TaC deformed much slower. The addition of these MC carbides led to a deformation rate divided by five to ten times. Now, creep behavior comparisons with commercial alloys are to be conducted. They will be performed soon.

Hydrogen-driven ultra-cryogenic deformation and embrittlement in Ti6Al4V alloy at 15 K

Hydrogen-driven ultra-cryogenic deformation and embrittlement in Ti6Al4V alloy at 15 K

In-situ experiment and numerical modelling of the intragranular and intergranular damage and fracture in plastic deformation of ductile alloys

In-situ experiment and numerical modelling of the intragranular and intergranular damage and fracture in plastic deformation of ductile alloys

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.

Superplastic deformation and macrozone behavior of the Ti60 high-temperature titanium alloy

Superplastic deformation and macrozone behavior of the Ti60 high-temperature titanium alloy

On the mechanism of plastic deformation in metastable TiZrHfNbx refractory high entropy alloys during tensile and sliding friction at 500 °C

Revealing the deformation mechanisms and their corresponding effect on the mechanical performance of the metastable TiZrHfNbx refractory high entropy alloys (RHEAs) is of great significance for the current engineering applications. A series of metastable TiZrHfNbx RHEAs was developed by applying the metastable engineering. The tensile and tribological properties were investigated at 500 °C systematically. The deformation mechanisms induced by the tensile stress and wear were elaborated in detail. From the experimental results, the Nb0.4 sample performs remarkable comprehensive performance with 445 MPa of YS, 937 MPa of UTS and 58.5 % of EL while Nb0.2 sample performs excellent tribological performance with lowest friction of coefficient and wear volume. It is concluded that metastable engineering with decreasing the Nb content successfully makes the matrix BCC phase unstable and improves the tensile properties and wear resistance at 500 °C. For the tensile tests, deformation bands, phase transformation and slip bands are regarded as the dominant deformation mechanisms. The co-deformation of the dual-phase microstructure for TiZrHfNb0.4 RHEA leads to excellent tensile performance. For the wear tests, the low-angle grain boundaries and nanocrystalline layer are reasonable for the lowest coefficient of friction and wear volume at 500 °C. This study not only developed a series of RHEAs with excellent tensile and tribological properties, but also expanded the understanding of the deformation mechanisms induced by stretching and friction.

Comparative study of elastic properties measurement techniques during plastic deformation of aluminum, magnesium, and titanium alloys: application to springback simulation

Comparative study of elastic properties measurement techniques during plastic deformation of aluminum, magnesium, and titanium alloys: application to springback simulation

High Strain Rate Deformation of Heat-Treated AA2519 Alloy.

This study examined the effects of heat treatment on the microstructure and dynamic deformation characteristics of AA2519 aluminum alloy in T4, T6, and T8 tempers under high strain rates of 1000-4000 s-1. A Split Hopkinson pressure bar (SHPB) was utilized to characterize the mechanical response, and microstructural analysis was performed to examine the material's microstructure. The findings indicated varied deformation across all three temper conditions. The dynamic behavior of each temper is influenced by its strength properties, which are determined by the aging type and the subsequent transformation of strengthening precipitates, along with the initial microstructure. At a strain rate of 1500 s-1, AA2519-T6 demonstrated a peak dynamic yield strength of 509 MPa and a flow stress of 667 MPa. These values are comparable to those recorded for AA2519-T8 at a strain rate of 3500 s-1. AA2519-T4 exhibited the lowest strength and flow stress characteristics. The T6 temper demonstrated initial stress collapse, dynamic strain aging, and an increased tendency for shear band formation and fracture within the defined strain rate range. The strain rates all showed similar trends in terms of strain hardening rate. The damage evolution of the alloy primarily involved the nucleation, shearing, and cracking of dispersoid particles.