Nanoindentation Behavior Research Articles

Iso-Material Manufactured 17-4PH Stainless Steel to Enhance the Nano-indentation, Corrosion, and Cavitation Erosion Behavior

Iso-Material Manufactured 17-4PH Stainless Steel to Enhance the Nano-indentation, Corrosion, and Cavitation Erosion Behavior

Nanoindentation behaviors of the AlCoCrFeNi2.1 eutectic high-entropy alloy: The effects of crystal structures

The AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA), as a kind of in-situ composite materials, have achieved good match of strength and plasticity due to its typical eutectic lamella structures. Although many previous studies have investigated the indentation behaviors of the AlCoCrFeNi2.1 EHEA, there are still some controversies about the hardness characteristic of different crystal structures, requiring further clarification. Accordingly, in this study, nanoindentation tests were conducted to investigate the indentation behaviors of different crystal structures (primary L12 phase, primary B2 phase, and the eutectic phase region). The residual indentation and the crystallographic orientations were characterized by the laser scanning confocal microscope, scanning electron microscope, and electron backscatter diffraction. The hardness in different crystal structures were comparatively analyzed and the material deformation mechanisms were discussed correspondingly. The statistic results showed that the eutectic phase region had the lowest hardness, and primary B2 phase had the highest hardness. Furthermore, the slip lines in the primary L12 phase were evenly distributed near the residual indentation, but the slip lines in the eutectic phase region were concentrated near the phase boundaries. These findings are expected to deepen the understanding of the microscale deformation behaviors of EHEAs.

Effect of temperature on the nanoindentation behavior of monocrystalline silicon by molecular dynamics simulations

Monocrystalline silicon (Si) undergoes complex phase transformations under external loads, significantly affecting its performance and processing. In this study, molecular dynamics (MD) simulations are performed from 1 to 900 K to explore temperature effects on the mechanical properties and deformation behavior of monocrystalline silicon during nanoindentation. Results indicate that hardness and elastic modulus decrease with rising temperature. At lower temperature, the activation of plastic deformation is delayed. The suddenly release of stored elastic energy manifests as a pop-in event. The indentation creates a quadruple symmetric phase transformation zone, primarily consisting of Si-II at the core, flanked by Si-XIII and bct-5. Increasing temperature advances the plastic deformation of the sample. High temperatures facilitate the formation and subsequent phase transformation of Si-XIII, reduce the stability of bct-5 during unloading, and promote the amorphization of silicon. At high temperatures, the dislocation of silicon nucleates at the subsurface, resulting in the formation of a substable phase. The anisotropy of deformation is evident from the atomic perspective, based on the orientation dependence of the phase transformation. This research provides new insights into the deformation behavior and phase transformations of monocrystalline silicon, supporting manufacturing and application of silicon products.

Strength Weakening and Phase Transition Mechanisms in Nanoindentation of Al/Mg-Layered Nanocomposites: A Molecular Dynamic Study

Molecular dynamics (MD) simulations were performed to investigate the nanoindentation behavior of Al/Mg-layered nanocomposites with varying layer thicknesses and Mg layer orientations in this study. The aim is to understand the weakening mechanisms at low layer thicknesses and the phase transition mechanisms associated with the dislocation slip angle in the Mg layer. Results indicate that the nanoindentation strength of nanocomposites increases with the layer thickness in the range of 1–10 nm, with the strength of 9.5 × 10−7 N at 10 nm being approximately 73% higher than that at 1 nm. This strength increase is mainly attributed to high interfacial stress, the higher percentage of amorphous atoms, weakened interatomic interactions, and the transition of adjacent interfaces to fully coherent interfaces that significantly reduce their ability to hinder dislocations at the low-layer thickness range. Additionally, in the initial deformation process, the hexagonal close-packed (HCP) phase of the Mg layer firstly transforms into the body-centered cubic (BCC) phase due to its lower energy barrier, followed by the emergence of a faced-centered cubic (FCC) phase driven by 1/3<1−100> dislocations. In the late stage of deformation, new dislocations are generated in the FCC phase and move along its slip planes, altering the dislocation direction. The FCC/HCP interfacial configuration also affects the HCP phase transition mechanism in the Mg layer. When the dislocation slip angle is 0°, the primary phase transition is the BCC phase, whereas a 45° slip angle results in the FCC phase. These findings will provide a guide for the preparation and manufacturing of new high-quality layered nanocomposites.

Evaluation of nano indentation behavior of TIG, MIG and diffusion bonded Inconel 718 and austenitic Stainless Steel 316L joint interface

The nanomechanical characteristics of Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and diffusion-bonded Inconel (IN718) and Austenitic Stainless Steel (SS 316L) were investigated. The nano hardness and elastic modulus of different weldments were evaluated using nanoindentation and compared. The results showed that intermetallic compounds (IMCs) and carbides were reduced with diffusion bonding. Moreover, maximum nano hardness and elastic modulus occurred in the welded zone (WZ) of TIG and MIG welded joints while at the bonding interface in diffusion bonding (DB). Lastly, the nano hardness of the bonding interface in diffusion-bonded was 11 % and 7 % lower compared to MIG and TIG welded joints.

Nanoindentation and relaxation behavior of nitrogen doped zirconium based bulk metallic glass

In this paper, the effect of nitrogen doping on the mechanical properties of Zr-based bulk metallic glasses (BMGs) was studied by nano indentation experiment, and the correlation mechanism between microstructure evolution and mechanical properties was analyzed. The results show that the serrations events exhibited by metallic glasses during nanoindentation are related to the loading rates. With the decreasing loading rate, more obvious serrations events occur in the loading segment, which is attributed to the sufficient time for shear bands to multiply and propagate at low rates. The addition of nitrogen will induce the generation of more flow defects. Compared with BMGs without nitrogen, the nitrogen-doped Zr-based BMGs exhibit more serration events due to introducing more flow defects to form the shear transformation zones (STZs) and subsequently facilitating the shear bands to multiply. The possible relationships between the structural evolution, shear band initiation and propagation, and relaxation behavior of nitrogen doped and non doped metallic glasses were discussed.

Nanoindentation and isothermal compression behaviour of Al–4Cu–Ni composites

The present investigation explores the nanoindentation and isothermal compression behaviour of Al–4Cu-xNi (x = 2, 4, 6, 8 and 10 wt%) Aluminium matrix composites produced by pressureless sintering technique. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses of sintered samples reveal the presence of core-shell type Al3Ni and Al3Ni2 intermetallic formation at the interface between Ni particulates and the Al–Cu matrix. Nanoindentation study shows hardness of 1.55 ± 0.15, 4.65 ± 0.44, 21.02 ± 0.42, 13.17 ± 0.13, 5.53 ± 0.89, 6.28 ± 0.19, 8.39 ± 0.14 GPa corresponding to α-Al matrix, Ni, Al3Ni2, Ni and Al3Ni2 interface, Al3Ni, and their respective interface. The composite containing 10 wt % Ni possesses the highest yield strength at room temperature. At 200 °C it could retain 54 % of its room temperature strength (91 MPa). The HR-TEM analysis shows that particulate and precipitation hardening was the predominant mechanisms during the initial stage of an isothermal compression. However, as the compression progressed, the pinning effect, dynamic recovery (DRV), and work hardening mechanisms became active. According to the current study findings, interface qualities substantially impact composite performance at both room temperature and elevated temperatures. The creation of strong intermetallic compounds (Al3Ni2 and Al3Ni) due to an intensive endothermic interaction between the Al and Ni particles is linked to this effect.

Effects of heat treatment on the nano-indentation, corrosion and cavitation erosion behavior of 17-4PH stainless steel by laser surface melting

The effects of heat treatment on the microstructure, residual stresses, nano-indentation behavior, the resistance to the corrosion and cavitation erosion (CE) of 17-4PH stainless steel (17-4PH SS) by laser surface melting (LSM) were thoroughly investigated. Experimental results showed that the samples were mainly composed of martensite phase, and the NbC precipitations formed after heat treatment. The distribution of NbC precipitations was more uniform in the sample (S3) after solution treatment 3 h at 1040 °C + aging treatment 3 h at 480 °C. The grain size was increased for the samples after heat treatment. This heat treatment processing significantly reduced the residual stresses generated from the LSM process, and the nano-indentation behavior of the LSM samples after heat treatment was improved compared to that of the LSM sample without heat treatment. The S3 sample displayed the highest corrosion resistance as indicated by the low corrosion current density (icorr), high pitting potential (Epit) and high polarization resistance (Rp). The CE resistance of samples after heat treatment in 3.5 wt% NaCl solution was higher than that of the sample without heat treatment. Among them, the S3 sample exhibited the highest CE resistance, and its CE mass loss was only 59.5 % of the sample without heat treatment. The excellent CE resistance resulted from the appropriate combination of mechanical properties, corrosion resistance and self-recovery ability of the passivation film.

Comparison of the corrosion and cavitation erosion behaviors of the cast and surface-modified manganese-aluminum bronzes in sodium chloride solution

Modified layers with refined and homogenized microstructure were obtained on a cast manganese aluminum bronze (MAB) by friction stir processing (FSP) and laser surface melting (LSM). In 3.5% NaCl solution, a much more protective film was formed and uniform corrosion occurred for the two surface-modified MABs. The corrosion rate of the cast sample was reduced by a factor of 29.73% after FSP and 51.35% after LSM. The cavitation erosion (CE) rate of the cast MAB was about 1.83 and 3.07 times larger than that of the FSP and LSM samples, respectively. The CE resistance increment was highly attributed to the improved hardness and enhanced nano-indentation behavior after FSP or LSM. For each MAB, the CE resistance decreased with extended pre-immersion time. Compared with the result of the correspondingly freshly-prepared sample, the CE rate was raised by a factor of 36.22%, 42.97% and 44.00% after 30 days’ pre-immersion for the cast, FSP and LSM MABs, respectively. For the cast and FSP MABs, mechanical impact was the leading factor accounting for CE degradation. For the pre-corroded samples, corrosion damage at the β and κ phases weakened the mechanical properties and thus triggered more grievous material exfoliation under CE. For the LSM MAB, CE-corrosion synergy dominantly gave rise to the CE damage. Corrosion at grain boundaries after pre-immersion also deteriorated the CE performance. The LSM MAB possessed the highest corrosion and CE resistances because the fine single-phase microstructure reduced the galvanic corrosion effect and crack propagation tendency under CE impact.

Effect of heat treatment on the microstructure and nanoindentation behavior of AlCoCrFeNi high entropy alloy

In the present work, the effect of annealing temperature on the phase evolution, morphology, and nanoindentation behavior of the equiatomic AlCoCrFeNi high entropy alloy (HEA) were investigated, and the correlation between the microstructure and nanoindentation behavior in the dendrite core (DC) and inter-dendrite (ID) regions was revealed. The DC and ID regions in the as-cast alloy are composed of disordered A2 particles and ordered B2 matrix. As the annealing temperature increases, the volume fraction of the face centered cubic (FCC) phase first increases and then decreases, leading to complete dissolution of FCC phase at 1200 °C. In addition, annealing at 700 and 800 °C results in the precipitation of the σ phase in the ID region. DSC and thermodynamic calculations were used to analyze the phase evolution of the alloy with temperature. Changes in morphology and phase constituent inevitably affect the mechanical properties of the alloy, which were characterized by nanoindentation for both ID and DC regions. The results show that the ID region displays higher nano-hardness than the DC region in the as-cast and 600–800 °C samples, but there is no difference in the 900–1200 °C temperature range.

Graphene oxide under the nanoscope: A comprehensive study of nanoindentation behavior

Graphene oxide membranes are expected to become one of the most important materials for technological applications due to their highly reactive surface, being directly related to their atomistic configuration. The understanding of its structure and physicochemical properties under mechanical deformation is becoming crucial in the development of new applications; however, the role of the different functional groups in the membrane and their response to external factors like indentation is still unclear. Nanoindentation experiments show elastic behavior when the penetration is small compared to the indenter radius and the membrane diameter. Molecular Dynamics simulations for large 3-layer graphene oxide membranes were carried out for a 50% oxidation content and the inclusion of epoxy and hydroxy groups. Simulations showed an elastic modulus similar to experimental values. After the elastic regime, the mechanical behavior is dominated by the evolution of functional groups. A quasi-elastic regime is uncovered, where unloading leads to self-healing of broken bonds. Finally, large indenter penetration leads to fracture, with fracture stress similar to experimental values.

Studies on Nano-Indentation and Corrosion Behavior of Diamond-Like Carbon Coated Stainless Steel (316L)

Studies on Nano-Indentation and Corrosion Behavior of Diamond-Like Carbon Coated Stainless Steel (316L)

Atomistic simulation of nanoindentation behavior of amorphous/crystalline dual-phase high entropy alloys

High-entropy alloys (HEAs) are a new type of multi-principal metal materials that exhibit excellent mechanical properties. However, the strength–ductility balance in the HEAs remains a challenge that needs to be addressed. The amorphous/crystalline (A/C) structure is a new design strategy to achieve high strength and excellent ductility of the HEAs. Here, the influences of amorphous layer spacing, indenter velocity, and indenter radius on the mechanical properties and microstructure evolution of the A/C dual-phase CoCrFeMnNi HEAs under nanoindentation were investigated by molecular dynamics (MD) simulation. The results indicate that the plastic deformation mechanism of the monocrystalline HEAs is mainly dominated by the nucleation and slip of dislocations, while the plastic deformation mechanism of the dual-phase HEAs is mainly dominated by the interaction between dislocations and amorphous phases. The results show that the average indentation force of the dual-phase HEAs increases with the increase of the amorphous layer spacing. The amorphous layer in the HEAs can hinder the expansion of dislocations, limiting them to the crystalline matrix between the two amorphous layers. The results also indicate that Young's modulus of the HEAs increases with the increase of the indentation velocity and indentation radius. However, the hardness of HEAs is positively correlated with the indenter velocity, and negatively correlated with the indenter radius. It should be noted that the critical indentation depth and critical indentation force for the plastic deformation of the dual-phase HEAs decrease with the increase of indenter velocity, which is opposite to that of the single-phase crystalline HEAs.

Ir–Zr coating through a pack cementation method for ultra-high temperature applications

An Ir–Zr intermetallic coating was prepared onto Re/Ir coated graphite through a pack cementation method. The microstructure, nanoindentation and ablation behaviors of the coating system were investigated. The Ir–Zr coating was about 20 μm thick and consisted of 4 intermetallic phases which showed a quasi-gradient transition in composition. Nanoindentation measurements indicated that most of the intermetallic phases had higher hardness but lower Young's modulus compared to pure iridium. By ablation test in a high-frequency plasma wind tunnel, the heat flux limit of the Ir–Zr coating was measured to be about 6.1 MW/m2, and the endurance time was about 100 s under this condition. The coating failed at ∼2240 °C during the ablation test when the iridium melted, but the unfused parts remained complete and in good adhesion with the iridium beneath. The average normal emissivity between 2 and 5 μm of the sample was measured to be ∼0.82 at around 2092 °C before failure, which was higher than pure iridium and bulk ZrO2.

Laser surface modification of the wrought and LPBF-printed biomedical Co-28Cr-6Mo alloys: Effects on nanoindentation and tribological behaviors

Laser surface modification of the wrought and LPBF-printed biomedical Co-28Cr-6Mo alloys: Effects on nanoindentation and tribological behaviors

The influence of chemical short-range order on the nanoindentation properties of high-entropy alloys prepared via laser powder bed fusion

Chemical short-range order (CSRO) plays an instrumental role in determining the mechanical properties of high-entropy alloys (HEAs). Current methods for controlling CSRO mainly focus on cast HEAs, which can not solve the problem of grain coarsening caused by homogenization treatments. Laser Powder Bed Fusion (LPBF), which has extremely high cooling rates, can suppress compositional segregation, refine grain structures, and achieve low CSRO. This offers a promising avenue for quantitatively controlling CSRO without the need for homogenization treatments. In this study, we investigate the CSRO of HEAs fabricated via LPBF and elucidate their influence on nanoindentation behavior. The results show that, at the low cooling rate, the average size of CSRO is 0.66 nm and they occupy 2.8% of the cross-sectional area, while at high cooling rate, the corresponding values are 0.92 nm and 9.9%, respectively, both of which are significantly smaller than those of cast HEAs. By analyzing samples with different CSROs, we observe that the hardness increases and then decreases with the increase of CSRO, primarily due to the preferential formation of dislocations in regions enriched with Cr-Mn-Ni. With the improvement of CSRO, both the size and quantity of Cr-Mn-Ni rich region gradually increased; subsequently, as multiple Cr-Mn-Ni rich regions tend to merge into one during the CSRO improvement, the size of the Cr-Mn-Ni rich region continued to increase while the quantity gradually decreased; when the size of the Cr-Mn-Ni rich region is moderate and widely dispersed, the dislocation density is higher with much more uniform distributions, which favorably improves nanoindentation hardness.

Atomic insights into the effects of Al element on the nanoindentation behavior of single-crystal FeNiCoCr-based multicomponent alloys

The effects of added Al element on the nanoindentation behavior of single-crystal FeNiCoCr-based multicomponent alloys (MCAs) loaded along different crystal orientations, were investigated via using molecular dynamic (MD) simulation. It is found that the added Al with a composition from ∼2.44 to ∼11.1 at. percentage, decreases the stacking fault energy (SFE) and enhances the lattice distortion of the face-centered cubic (FCC) alloys, accordingly affecting the dislocation-medium plastic behavior. Especially, via using the Hertz elastic theory to fit the load-displacement curve, the onset of incipient plasticity triggered by first dislocation nucleation exhibits a significant dependence on the Al concentration. As increasing the Al contents, the critical force for incipient plasticity decreases, mainly owing to the Al-enhanced lattice distortion reducing the atomic displacement necessary for homogeneous dislocation nucleation. Moreover, due to the different Schmidt factors and various slip systems activated for plasticity, dislocations are most difficult to be generated when the (111) lattice plane is indented, but easiest when the (100) plane is indented, leading to the orientation-dependence nano-mechanical response of these MCA. This suggests that whether the nanoindentation is easy in one orientation is trivially connected to the crystalline structure, and mostly has nothing to do with the chemical composition altered by the added Al. Besides, due to the lowered SFE value by the Al added to the alloy, the generation and propagation of extended dislocation structures (composed of Shockley partials and in-between stacking faults) that transfer most plastic strains on deformation, are significantly promoted, consequently increasing the plastic zone size beneath the indenter and lowering the nano-harness of the Al-doped specimens. The simulation results verify the strong composition dependence of mechanical properties for single-crystal MCAs and contribute to the composition design of MCAs for real applications.

The Influence of Crystallographic Orientation and Grain Boundary on Nanoindentation Behavior of Inconel 718 Superalloy Based on Crystal Plasticity Theory

The crystal plasticity finite element method (CPFEM) is widely used to explore the microscopic mechanical behavior of materials and understand the deformation mechanism at the grain-level. However, few CPFEM simulation studies have been carried out to analyze the nanoindentation deformation mechanism of polycrystalline materials at the microscale level. In this study, a three-dimensional CPFEM-based nanoindentation simulation is performed on an Inconel 718 polycrystalline material to examine the influence of different crystallographic parameters on nanoindentation behavior. A representative volume element model is developed to calibrate the crystal plastic constitutive parameters by comparing the stress-strain data with the experimental results. The indentation force-displacement curves, stress distributions, and pile-up patterns are obtained by CPFEM simulation. The results show that the crystallographic orientation and grain boundary have little influence on the force-displacement curves of the nanoindentation, but significantly influence the local stress distributions and shape of the pile-up patterns. As the difference in crystallographic orientation between grains increases, changes in the pile-up patterns and stress distributions caused by this effect become more significant. In addition, the simulation results reveal that the existence of grain boundaries affects the continuity of the stress distribution. The obstruction on the continuity of stress distribution increases as the grain boundary angle increases. This research demonstrates that the proposed CPFEM model can well describe the microscopic compressive deformation behaviors of Inconel 718 under nanoindentation.

Effect of Annealing Temperature and Thickness of Magnetron Sputtered Ni/Ti Film on Its Microstructure and Nanoindentation Behavior

Effect of Annealing Temperature and Thickness of Magnetron Sputtered Ni/Ti Film on Its Microstructure and Nanoindentation Behavior

The effects of normal load on the dry-sliding, micro-scratch and nanoindentation behaviors of the Zr-based bulk glassy alloys

In this work, the macro-sliding, micro-scratch and nanoindentation behaviors of the Zr55Cu30Al10Ni5 bulk glassy alloy (BGA) were investigated. It was found that the frictional coefficient and wear rate of the BGA in the dry-sliding test increase with the increasing normal load, and the wear mechanism includes abrasive and oxidative wear. The micro-scratch test results show that the plastic deformation of the alloy and the density of shear bands at the edge of scratch scar increase with the increase in normal load. The friction mechanism between the indenter and the BGA shifts from stick-slip friction to ploughing friction and to micro-cutting as the applied normal load elevates. The nanoindentation result reveals that increasing the normal load leads to the plastic deformation accumulation, and the decreasing elastic modulus and hardness, which are related to the increase in the free volume and shear bands during the deformation process.