Compressive Deformation Behavior Research Articles

In-situ synchrotron diffraction study on compressive deformation behavior of Mg92Y5Ni3 alloy mostly composed of LPSO

The compressive deformation behavior of the as-cast and as-extruded Mg92Y5Ni3 (at.%) alloy mostly composed of long period stacking ordered (LPSO) phase was studied by in-situ synchrotron radiation combined with the analysis of deformation traces after compression at different applied stress. The as-cast alloy has random texture, while the as-extruded alloy has a typical basal texture with basal plane parallel to extrusion (compression) direction. Prior to macro-yielding, some softly oriented grains are preferentially plastically deformed, leading to micro-yielding. The micro-yielding behavior of both as-cast and as-extruded alloys is controlled by basal slip, the as-extruded alloy has higher micro-yielding strength than the as-cast alloy. The activated deformation mode near the macro-yielding point is prismatic slip in both as-cast and as-extruded alloys, and as the hard oriented grains dominate in the as-extruded alloy, the compressive yield strength of the alloy is increased from 217 MPa to 535 MPa after extrusion. The kinking activated following the prismatic slip can introduce a large number of dislocations in the as-extruded alloy, resulting in high strain-hardening rate of 3000 MPa, high ultimate compressive strength of ∼800 MPa and plastic strains above 10%.

Room temperature compressive superplasticity of low density steel

The present work deals with the room temperature compressive deformation behavior of a low density steel holding an apparent density of 6.8 gr/cm3. Surprisingly, it was found that the experimented materials tolerated a high amount of compressive true strain (∼2.5) without the occurrence of any micro-cracking or macro-localized shearing. Step by step study of the interrupted microstructures indicated the continuous and progressive development of the substructure in the course of room temperature compressive deformation. The extended dynamic recovery was justified considering the high stacking fault energy of the material and was followed by the occurrence of continuous dynamic recrystallization where the final microstructure was composed of ultrafine and equiaxed grains. Interestingly, the corresponding flow behavior was greatly affected by such specified microstructure evolution and an appreciable strain softening was obtained over a wide range of strain.

Study on the compressive deformation behavior of a basal textured AZ31 magnesium alloy from the perspective of local strain

For basal textured magnesium alloy subjecting to in-plane compression, the deformation is complicated since twinning, dislocation slipping and their intersecting are involved. In this work, a high-resolution digital image correlation (HR-DIC) technique combined with electron backscatter diffraction (EBSD) was used to quantitatively study the deformation behavior of AZ31 alloy in in-plane compression. Grain-scale local strain characteristics were emphasized. It is found that the local strain in the twined region is homogeneous and will not continuously increase with the applied nominal compression strain if no dislocation slipping is activated. When twinning is accompanied by dislocation slipping in the deformation of magnesium alloys, which is actually the common case, the strain contribution by the twinning can be calculated by transferring its shear from the twin frame to the sample frame. The results of this work can be beneficial for further understanding of deformation mechanism of magnesium alloy and the development of physics-based simulation models.

Effects of sample diameter, aspect ratio, and strain rate on compressive deformation and fracture behavior of Zr50Cu34Al8Ag8 metallic glass

In this paper, Zr50Cu34Al8Ag8 metallic glass bars with diameters of 2, 3, and 4 mm were prepared by copper mold suction casting. The compressive mechanical properties of metallic glass samples having different diameters, aspect ratios, and strain rates were tested by a universal testing machine. The microstructure of metallic glass samples was analyzed by X-ray diffractometer, scanning electron microscope, and transmission electron microscope. The experimental results show that the mechanical properties of Zr50Cu34Al8Ag8 metallic glass improve with decreasing sample diameter, aspect ratio, and strain rate. The maximum compressive strength, ultimate strain, and plastic strain of 1991.2 MPa, 7.95%, and 4.99% were respectively achieved for the metallic glass sample of φ = 2 mm. The main reason for the metallic glass's superior mechanical properties is its higher free volume content. For the metallic glass samples with the same diameter and different aspect ratios, the compressive strength and ultimate strain of the metallic glass with φ = 3 mm and aspect ratio = 1 is the largest, which are 2052.8 MPa and 15.2%, respectively, and the plastic strain is 11.09%. The improvement of mechanical properties of metallic glass samples is primarily attributed to the change of stress state. When the strain rate is 3 × 10−4 s, the compressive strength and ultimate strain of the sample are 1851.2 MPa and 4.09% respectively. This study will help to improve our understanding of the compression deformation and fracture behavior of metallic glasses, as well as promote their application.

Deformation mechanisms in the directionally solidified nickel-based CM247LC at room temperature

ABSTRACT After solutionizing and aging at 980°C for various durations, the compressive deformation behaviour and mechanisms of the directionally solidified nickel-based superalloy CM247LC are investigated at room temperature. Experimental results show that the yield strength decreases gradually from 991 ± 1.2–672 ± 7.5 MPa with increasing the γ′ precipitate size from 145 ± 2–604 ± 19 nm. Transmission electron microscope observations on the slightly deformed specimens reveal that, in contrast to previous researches, plastic deformation of all the specimens is controlled by strongly coupled dislocations cutting through γ′ precipitates. Based on these experimental results, the relationship between the yield strength and precipitate size is discussed.

Compression Performance and Deformation Behavior of 3D-Printed PLA-Based Lattice Structures.

The aim of this study is to fabricate biodegradable PLA-based composite filaments for 3D printing to manufacture bear-loading lattice structures. First, CaCO3 and TCP as inorganic fillers were incorporated into a PLA matrix to fabricate a series of composite filaments. The material compositions, mechanical properties, and rheology behavior of the PLA/CaCO3 and PLA/TCP filaments were evaluated. Then, two lattice structures, cubic and Triply Periodic Minimal Surfaces-Diamond (TPMS-D), were geometrically designed and 3D-printed into fine samples. The axial compression results indicated that the addition of CaCO3 and TCP effectively enhances the compressive modulus and strength of lattice structures. In particular, the TPMS-D structure showed superior load-carrying capacity and specific energy absorption compared to those of its cubic counterparts. Furthermore, the deformation behavior of these two lattice structures was examined by image recording during compression and computed tomography (CT) scanning of samples after compression. It was observed that pore structure could be well held in TPMS-D, while that in cubic structure was destroyed due to the fracture of vertical struts. Therefore, this paper highlights promising 3D-printed biodegradable lattice structures with excellent energy-absorption capacity and high structural stability.

4D-XCT and Digital Volume Correlation of Flax Fibre Composites Under Compressive Load After Relaxation

In-situ testing capabilities of lab-scale industrial computed tomography are rapidly improving. In the present study, the compressive deformation behaviour of a flax fibre-reinforced epoxy composite is studied in an in-situ compression test with stepwise loading, during 3D imaging with X-ray Computed Tomography (XCT). The 3D volumes are processed with Digital Volume Correlation (DVC) to identify the deformation of each loading step. The natural variability of the flax texture served as an adequate speckle pattern for DVC. The precision and accuracy of the DVC were investigated prior to the analysis of the deformation volumes by digitally deforming the reference undeformed volume with a known strain of 2 %. The calculated global strain was in good agreement with the digitally applied strain. Subsequently, DVC was applied to the acquired reference and deformed volumes and the analysis was focused on the 3D strain field evolution between the consecutive loading steps. Strain localization regions were observed in the axial strain εzz and the in-plane strain εxx. In the subsequent loading steps, the onset of compressive fibre-kinking is observed as a rotating fibre inside the magnified strain region. The 3D strain field evolution allows for a better understanding of the deformation and failure mechanisms at the meso/micro-scale in natural fibre reinforced composites under compressive loads.

Compressive deformation behavior and energy absorption characteristic of additively manufactured sheet CoCrMo triply periodic minimal surface lattices

CoCrMo sheet triply periodic minimal surface (sheet-TPMS) lattices with two different topologies (Neovius, IWP) were fabricated by laser power bed fusion (LPBF). Compressive behavior and energy absorption characteristic for each topology and direction were investigated. The unique pore channel structures of the fabricated Neovius and IWP lattices were well formed. The microstructural observation revealed that fine cellular substructures existed inside the sheets, and most of their constituent phases were confirmed to be the FCC phase. The results of the compression tests demonstrated that Neovius lattice had higher yield strength and first peak strength than IWP lattice, regardless of the compressive direction. As for the stress–strain curves of the lattices, an abrupt stress drop was found in neither of the two topologies. A comparison of the energy absorption characteristics confirmed that Neovius lattice had higher energy absorption efficiency and ideality than IWP lattice. The deformed structures showed that Neovius lattice displayed a gradual collapse mode, whereas a layer-by-layer compaction mode was indicated in IWP lattice. After the deformation, Neovius showed an evenly distributed and high fraction of the HCP phase caused by strain-induced martensitic transformation. The topology of lattice and strain-induced martensitic transformation effects on the compressive mechanical responses of the LPBF-built TPMS lattices were also discussed.

Compressive deformation behaviour and toughening mechanisms of spark plasma sintered NiAl-CNT composites

Carbon nanotube (CNT)-reinforced NiAl intermetallic composites were produced via powder metallurgy, particularly spark plasma sintering. The aim of this study was to evaluate the room temperature compressive behaviour of the sintered NiAl-CNT composites with a focus on the toughening mechanisms of the CNT reinforcement and the resulting microstructures. Remarkably, the NiAl-0.5 wt% CNT composites exhibited a balanced combination of strength and toughness despite a trade-off tendency, due to the presence of both coarse and fine bimodal grains in its microstructure. Mechanical properties of 831 MPa, 429 MPa and 360 HV were recorded for the ultimate compressive strength (UCS), compressive yield strength (CYS) and microhardness of the NiAl-0.5%CNT intermetallic composites, respectively, along with a compressive strain of 12% being higher than the unreinforced NiAl.

Dynamic recrystallisation and constitutive equation in hot deformed AISI H10 tool steel

ABSTRACT The compression deformation behavior of AISI H10 (DIN 32CrMoV12-28) hot work tool steel was investigated at temperatures ranging from 900°C to 1200°C and strain rates from 0.01 to 1 s−1. True stress-strain curves showed that a decrease in strain rate or increase in deformation temperature can promote the occurrence of DRX. It was found that the characteristic strains and stresses decrease with an increase in temperature or decrease in strain rate. The σc/σp ratio takes an average of 0.94; and the ϵc/ϵp ratio lies in range of 0.48-0.65 (average of 0.53). This suggests that DRV in H10 is not extensive and DRX starts at strains about half of the peak strain. However, the extensive softening by DRX keeps σp close to σc. Using the hyperbolic-sine constitutive equation, the deformation activation energy was calculated to be about 435.76 kJ mol−1.

Developing harmonic structure in CoCrFeMnNi high entropy alloy to enhance mechanical properties via powder metallurgy approach

The FCC structured CoCrFeMnNi high entropy alloy (HEA) has attracted great attention due to its excellent ductility and strain hardening ability, but the lowest yield strength is insufficient for structural applications. To achieve high strength and ductility, we developed a new strategy called harmonic structure (HS) consisting of soft coarse and hard fine grains via controlled mechanical milling time. The SEM and EBSD microscopic characterizations reveal that the formation of HS from surface to the interior of powder is due to a difference in the degree of plastic deformation. The hardness of HS HEAs increased with increasing distance from center to surface regions due to a reduction in grain size. Compared with the homogeneous HEA, the yield strength of HS HEAs increased from 370 MPa to 730 MPa and 760 MPa due to grain boundary strengthening, dislocation strengthening, and twin boundary strengthening effects. While HS HEAs exhibited enhanced strain hardening ability due to gradient structure with their mechanical incompatibility provide back stress strengthening. Furthermore, the compressive deformation behavior of homogeneous and HS HEAs was analyzed by microstructural evolution.

Investigation of conventional and asphaltic underlayment track behaviors subjected to freight train load: Mechanistic approach

The load characteristics in terms of the carrying capacity and the train operation speed limit Indonesia's conventional track capability. In this study, the behaviors of Indonesia's conventional tracks and the proposed asphaltic underlayment tracks under cyclic loading conditions of the low-speed Babaranjang (long-chain coal) freight trains have been evaluated using the finite element package Abaqus/CAE considering linear elastic behavior of materials. The numerical modeling was applied on three different layer thicknesses of sub-ballast in Indonesia's conventional tracks and three different layer thicknesses of asphalt in asphaltic underlayment tracks to investigate the vertical compressive stress, horizontal-vertical-maximum strain, and deformation behaviors. According to the numerical simulation, the measurements indicate that the asphaltic underlayment tracks are superior to Indonesia's conventional tracks. Furthermore, a 15 cm of asphalt layer in the asphaltic underlayment tracks demonstrates promising performance in the future of Indonesia's railway systems. The asphaltic underlayment tracks are expected to serve the heavier and higher speed Babaranjang freight trains with longer service life and lower life cycle cost than Indonesia's conventional tracks.

Compressive deformation and electrochemical analysis of Ti4AlxCo alloy

Ti4AlxCo (wt%) (x = 0%, 2%, 4%, and 6%) were synthesized via powder metallurgy route. Effect of Co content on the phase formation, microstructural transformation, compressive deformation and electrochemical behaviour of the alloy were investigated. Phase formation and microstructural analysis were done with the help of XRD and FESEM respectively. Compression test was performed to investigate the yield strength and modulus of elasticity of the alloy. Synthesized alloys were analyzed by electrochemical method to probe their resistance to corrosion in the Hank’s solution. XRD test confirms the formation of Ti2Co phase in the alloy which volume fraction increases with the increment of Co content. Leafy columnar structure of Ti2Co phase was clearly observed in the microstructure of the alloy containing Co. Compressive yield strength (σy) and elastic modulus (E) of Ti4Al sample are about 45% and 25% lower than the sample made of commercially pure (CP) Ti. Addition of Co content improves σy as well as E. However, alloys containing more than 2 wt% of Co have higher elastic modulus than Ti6Al4V which may be a concern to use them as a bone scaffold. In Tafel plot, corrosion current density (Icorr) shifts towards the higher value with the increment of Co content causing the reduction of corrosion resistance.

Effect of carrier gas species on the microstructure and compressive deformation behaviors of ultra-strong pure copper manufactured by cold spray additive manufacturing

Cold spray (CS) which has recently become a promising additive manufacturing (AM) technology, was used to fabricate ultra-strong pure copper. In addition, the effects of carrier gas species on the microstructural characteristics, mechanical properties and deformation mechanisms were systemically explored. The CSAM copper manufactured with N2 carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner particles. With He carrier gas, a homogeneous grain structure consisting of ultra-fine grains in most areas was obtained. Compressive tests showed that N2 and He carrier gasses enabled ultra-high yield strengths of 340 and 415 MPa, respectively. These values are comparable to severely plastic deformed copper, which has extremely low ductility and shape fidelity. On the other hand, both samples showed a strain-softening phenomenon that does not commonly occur at room temperature. The deformation microstructures revealed that dynamic recovery (DRV) and dynamic recrystallization (DRX) phenomena were generated despite being deformed at room temperature. Based on the above findings, the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were discussed. Furthermore, the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation .

Study on the Compressive Deformation Behavior of a Basal Textured Magnesium Alloy from the Perspective of Local Strain

Study on the Compressive Deformation Behavior of a Basal Textured Magnesium Alloy from the Perspective of Local Strain

Plastic anisotropy and compressive deformation behavior of Zinc prepared by sintering using fine particles

In recent years, Zn can potentially be applied as biomaterials owing to its excellent biocompatibility and biocorrosion resistance. However, Zn has poor strength and large plastic anisotropy due to its hexagonal close-packed (HCP) structure. In this study, to increase the strength and plastic isotropy, fine-grained Zn polycrystal was produced by spark plasma sintering from Zn fine particles prepared by arc plasma method. Yield strength and the plastic anisotropy of the sintered Zn were evaluated by compression tests and Vickers indentation. The yield strength of the sintered Zn was significantly higher than the as-cast Zn. Moreover, the plastic anisotropy of the sintered Zn was small because of its fine grain and random texture.

Effect of hydrogen on microstructure evolution and deformation behaviors of Ti-2Fe-0.1B alloy

A low-cost Ti-2Fe-0.1B alloy with high performance was manufactured and hydrogenated in this study. The effect of 0.3 wt% hydrogen addition on microstructure evolution, compression deformation behavior at room and high temperature of Ti–2Fe–0.1B alloy has been investigated. Results indicated that lamellar αL structure along with martensite α′ are formed after hydrogenation compared with initial equiaxed grains, and the fraction of β phase increased from 4.95% to 30.1%. Obvious phase transformation αeq→αH+ βH, β→βH during hydrogenation and βH→α + δ, αH→α + δ during subsequent cooling occurred. The hydrogenated Ti-2Fe-0.1B alloy is characterized by hardening effect during compression deformation at room temperature along with the loss of ductility due to the solid solution strengthening by hydrogen atoms and presence of hydride δ. However, peak flow stress of hydrogenated Ti-2Fe-0.1B alloy decreased from 49 MPa to 29 MPa extremely during compression deformation at 973 K, which can be attributed to the high volume of β phase induced by hydrogenation, as well as the promotion of dynamic recovery and dynamic recrystallization.

Compressive deformation of as-extruded LPSO-containing Mg alloys at different temperatures

This work investigates the compressive deformation behavior of as-extruded Mg-6Gd-1.6Y–1Zn-0.4Zr (VZ61) and Mg-6Gd-4.8Y–3Zn-0.4Zr (VZ63) alloys via uniaxial compressive tests at various deformation temperatures. At room temperature, compared with the VZ61 alloy, the compressive yield strength of the VZ63 alloy were obviously enhanced due to its increased amount of LPSO phase. Both alloys exhibited a three-stage strain hardening feature. The strain hardening rate first sharply decreases (stage I), then continues to increase at a slower rate (stage II) and finally decreases (stage III). At stage III, a larger number of dislocation accumulation around the kinked LPSO phase resulted in a higher strain hardening rate for VZ63 alloy than that for VZ61 alloy. During high temperature compression, the true stress–strain curves showed that the flow stress gradually reduced with increasing temperature and also the reducing of strain rate, and the VZ63 alloy displayed a higher peak stress than VZ61 alloy. Constitutive equations were constructed based on the true stress–strain to better understand the relation among flow tress (σ), strain rate (ε⋅) and deformation temperature (T) in VZ alloys during hot deformation. The results showed that the VZ63 alloy had a lower deformation activation energy (Q = 255.6 kJ/mol) than VZ61 alloy (Q = 395.5 kJ/mol). The DRX kinetic models of the VZ61 and VZ63 alloys were also established, indicating that the VZ63 alloy was more prone to DRX with a higher volume fraction of dynamically recrystallized grains (XDRX) at the same deformation conditions.

Deformation behavior of Zr33Hf8Ti6Cu32Ni10Co5Al6 high-entropy bulk metallic glass and Cu47Zr47Al6 low-entropy bulk metallic glass at room and high temperatures

Compressive deformation behavior at room temperature and the high temperatures was studied for Zr33Hf8Ti6Cu32Ni10Co5Al6 developed HEBMG and Cu47Zr47Al6 BMG alloys. Compressive strain-stress curves at room temperature showed that with the development of HEBMG, ductility and fracture stress improved by 58% and 5.4%, respectively. The high density of shear bands in the HEBMG compared to the BMG had a significant relationship with their mechanical properties, which indicated that the ductility of HEBMG is higher than BMG. The high temperatures deformation studies were performed at strain rates of 2.5×10−4s−1, 2.5×10−3s−1, and 5.0×10−5s−1 and at temperatures of 710K and 730K. The hot deformation behavior of both alloys was similar, but HEBMG with standed more stresses than BMG (under similar conditions). Considering the free volume theory, for the results obtained from stress-strain curves at high temperatures, the maximum value of activation volume was equal to V = 0.3076 nm3 for HEBMG. Also, viscosity has shown a decreasing trend with increasing strain rate, however HEBMG samples had a higher value of viscosity than BMG samples. Deformation behavior of the HEBMG at high strain rates has been closer to Newtonian flow compared to BMG.

Temperature Dependency on the Microscopic Mechanism in the Normal Direction of Wrought AZ31 Sheet under Dynamic Compressive Behavior.

In order to analyze the competitive relationship of different deformation mechanisms in wrought AZ31 magnesium alloy, the dynamic compressive experiments were conducted by a Split Hopkinson Pressure Bar (SHPB) apparatus and a resistance-heated furnace in the range of temperature between 20 and 350 °C at the strain rate of 1000 s−1. With the help of Electron Backscattered Diffraction (EBSD) observation, theoretical calculated Schmid Factor (SF), Critical Resolved Shear Stress (CRSS), and critical equivalent stress (σ0.2), the dynamic compressive deformation behavior and corresponding mechanism of wrought AZ31 magnesium alloy along the normal direction (ND) were revealed in the current study. The results demonstrate that the c-axis of grains are gradually reoriented parallel to the normal direction of wrought AZ31-ND sheet with the temperature increasing, except the dynamic recrystallization (DRX) mechanism was activated or grains grew up. The non-basal slip and tension twinning are respectively the predominant deformation mechanisms at lower temperatures (≤250 °C) and higher temperatures (≥250 °C). The predominant type of DRX mechanism of wrought AZ31-ND sheet is rotational dynamic recrystallization (RDRX), which is regarded as an obstacle for the kernel misorientation concentration region enhancement.