Mechanical Anisotropy Research Articles

The impact of sidewall copper grain condition on thermo-mechanical behaviors of TSVs during the annealing process

With the drastic reduction of the TSV diameter leading to a critical dimension comparable to the Cu-filled grain size, the grain condition strongly influences the thermo-mechanical behavior of the TSV. In this work, the TSV-Cu cross-section with different grain sizes is characterized by EBSD, confirming that the sidewall grain size (0.638–1.580 μm) is smaller compared to other regions (1.022–2.134 μm). A finite element model (FEM) considering copper grains is constructed by using Voronoi diagrams to investigate the effect of sidewall grain size as well as area on the thermo-mechanical behavior during annealing. The material parameters in the FEM are optimized through nanoindentation inversion and considering the mechanical property anisotropy of copper grains. The yield strength σy and hardening exponent n of TSV-Cu are 74.6 MPa and 0.514. The simulation results indicate that the protrusion of TSV-Cu after annealing tends to increase initially and then decrease with smaller sidewall grain size and area. The maximum increase in protrusion caused by the two variables can reach 6.74% and 14.6%, respectively, relative to the average grain condition. Additionally, the simulation results were validated by quantifying grain boundaries in TSV-Cu samples with varying grain sizes.

Theoretical investigation of structural, electronic, mechanical, surface work function and thermodynamic properties of La1-xMxB6 (M = Ba, Sr, Ca) compounds: Potential plasma grid materials in N-NBI system

This study employs first-principles calculations to investigate the structural, electronic, and mechanical properties of La1-xMxB6 (M = Ba, Sr, Ca), focusing on the surface work function, elastic constants, bulk modulus, shear modulus, Young’s modulus, Debye temperature, and melting point. The results indicate that doping generally leads to a reduction in the surface work function, with La0.375Ba0.625B6 achieving a work function as low as 1.27 eV. The influence of doping concentration on the mechanical properties and anisotropy is analyzed, revealing that La1-xMxB6 and La0.5Sr0.5B6 exhibit oscillatory changes related to the layered structure of the dopants. Brittleness is assessed through the B/G ratio and Poisson’s ratio. Thermodynamic analysis shows that the melting points of these compounds exceed 2000 K. These findings provide useful references for choosing cesium-free electrode materials applied for plasma-facing applications in neutral beam injection.

Effect of asymmetric cross-rolling on the microstructure, texture, and mechanical anisotropy of Fe–0.07C steel

Effect of asymmetric cross-rolling on the microstructure, texture, and mechanical anisotropy of Fe–0.07C steel

Remelting-based microstructure engineering in laser powder bed fusion: A case study in 316L stainless steel

In laser powder bed fusion (LPBF), the formation of bulky columnar grains often results in undesirable mechanical anisotropy. Here, we demonstrate a new strategy to control the microstructure in LPBF through tuning melt pool overlaps without changing energy densities and scan patterns. Using 316L stainless steel as an example, we generate a wide range of grain sizes and morphologies. The underlying mechanism is associated with the retainment or elimination of newly nucleated grains at a melt pool during the formation of subsequent melt pools. The propensity of retainment or elimination of grains is largely dependent on the extent of melt pool overlaps because the grains are prone to nucleate at the free-surfaces of melt pool boundaries. This facile strategy could be applicable to a wide range of metallic alloys, paving a new way for microstructure engineering in additive manufacturing.

Sculpting Mechanical Properties of Hydrogels by Patterning Seamlessly Interlocked Stiff Skeleton

AbstractFunctional soft materials, especially hydrogels have been widely developed to achieve various soft structures and machines. However, synthetic hydrogels commonly show formula‐dependent mechanical properties to fulfill the requirements of mechanical elasticity, stiffness, toughness, and tearing‐resistance for adapting to complex application scenario. Inspired by heterostructures and materials found in nature such as leaves and insect wings, a sequential photopolymerization process combined with site‐selective patterning exposure is reported to prepare programmable hydrogels with locally heterogeneous reinforcement skeletons, i.e., interpenetrating double networks. The heterogeneous interface between soft matrices and stiff skeletons is seamlessly interlocked through strong multiple hydrogen bonds induced by phase transition. By harnessing the size, shape, and distribution of the patterned stiff skeletons, a wide range of mechanical properties of hydrogels including modulus (0.32–5.92 MPa), toughness (0.15–18 kJ m−2), dissipated energy (1–100 kJ m−3), impact resistance, and mechanical anisotropy can be readily sculpted within one material system without needing design and optimization of the complex and elusive material formulation on demand. It is believed that this simple yet powerful method relying on heterogenous patterning would guide the development of functional hydrogel materials with programmable mechanical properties toward potential engineering applications, such as damping and flexible circuits.

A mechanical calculation model for the nonlinear mechanical behavior of the metal rubber clamp in aero engine

As an important pipeline support component, metal rubber clamp is mainly used for pipeline connection, fixation and vibration isolation. At present, the researches on hysteretic and stiffness characteristics of metal rubber clamps in aero engines are still in their infancy. This work aims to develop a nonlinear mechanical calculation model for metal rubber clamps to effectively capture the nonlinear mechanical properties, such as hysteresis characteristics and variable stiffness behavior. The equivalent stiffness model of metal rubber clamps was established by introducing tightening torque and friction between metal wires as control variables, and the mechanical behavior under repeated loads is analyzed by combining the force and deformation relations of typical hysteretic curves. By comparing the measured hysteretic curve and natural frequencies, the proposed equivalent stiffness model of a metal rubber clamp is verified. This also suggests that the proposed model can effectively simulate the dry friction damping characteristics of metal rubber. In addition, the effects of tightening torque and friction coefficient on hysteretic characteristics and stiffness are also analyzed. The aim of this study is to develop mechanical anisotropy tests integrated with equivalent numerical simulation techniques to elucidate the mechanical characteristics of the aero engine clamp. The research can provide theoretical support for the structural design of metal rubber clamps.

Investigation of Single and Double Pulse Techniques on Microstructure and Mechanical Anisotropy of Inconel 686 Component Fabricated by Wire Arc Directed Energy Deposition

Investigation of Single and Double Pulse Techniques on Microstructure and Mechanical Anisotropy of Inconel 686 Component Fabricated by Wire Arc Directed Energy Deposition

Effect of an AC-DC composite longitudinal magnetic field on the microstructure and mechanical properties of WAAM Al-5 %Mg alloy

To address issues of poor forming accuracy, high porosity, and inadequate mechanical properties in wire arc additive manufacturing of aluminum alloys, this study applied external direct current (DC) and alternating current (AC) composite magnetic fields (ECMF) (AC+DC) in cold metal transition wire arc additive manufacturing (CMT-WAAM) of Al-5 % Mg alloys. The aim was to enhance the quality of forming and overall mechanical properties of the deposited specimens. Optimal ECMF (AC+DC) parameters-DC 3 A, AC 1 A, and alternating frequency 100 Hz-were determined through orthogonal experiments. Results showed that ECMF (AC+DC) facilitated arc expansion and stirred the molten pool via Lorentz force generation, thereby accelerating molten flow and improving forming precision. Compared to specimens without ECMF (AC+DC), those with ECMF (AC+DC) exhibited reduced porosity (1.07 % to 0.31 %, a decrease of 71.03 %) and finer grain size in the deposited layer (84.80 ±30.5μm to 69.10±25.1μm, an 18.51 % decrease). Additionally, average microhardness increased (83.83 HV to 96.70 HV, a 15.35 % increase), transverse tensile strength improved (239.66±1.6 MPa to 263.00± 1 MPa, a 9.86 % increase), and elongation at break enhanced from 25.50±3.8 % to 27.17±0.33 %. Longitudinal tensile strength also rose (232.33±14.33 MPa to 248.33±8.33 MPa, a 6.88 % increase), with elongation at break increasing from 19.00±7.5 % to 19.40±4.2 %. Moreover, the mechanical properties' anisotropy decreased. Consequently, ECMF (AC+DC) significantly enhanced the overall properties of CMT-WAAM Al-5 % Mg alloy deposition, providing valuable insights for extending engineering applications of Al-5 % Mg alloy WAAM.

Unveiling the mechanical anisotropy and related deformation mechanisms of heterostructured Mg alloy laminate with unique texture feature

In this study, a well-bonded AZ31/ZK60/AZ31 sandwich-structured laminate was prepared using extrusion. Microstructural heterogeneities in grain size, precipitate phases, and texture were evident between the constituent layers. Tensile testing revealed significant mechanical anisotropy in the laminates along the extrusion direction (ED), transverse direction (TD), and 45° directions, with the 45° direction samples exhibiting the highest tensile ductility, while ED and TD samples showed similar high strength. In-situ electron backscatter diffraction and slip trace analysis indicated that the heterogeneities in grain size and precipitates had minimal influence on the mechanical anisotropy of the laminates. Instead, texture emerged as the primary influencing factor, as it affected the initiation difficulty of basal slip and extension twinning mechanisms in various directions, thereby influencing the deformation coordination between the successive layers and resulting in varied mechanical responses in different directions.

Effect of Variable Gravity Field on Dual Component Convection in a Couple Stress Fluid Saturated Anisotropic Porous Layer With Temperature‐Dependent Heat Source

ABSTRACTThis study examines how gravity fluctuations, the couple stress parameter, anisotropic parameters, and heat source collectively influence dual‐component convection in the porous layer. The linear analysis is conducted utilizing the normal mode technique. The authors proposed three categories of gravity fluctuation, namely: (a) linear, (b) parabolic, and (c) exponential. Expressions for both stationary and oscillatory Rayleigh numbers are derived using the Galerkin approach. Neutral stability curves for both stationary and oscillatory modes are analyzed, with graphical representations to show the effects of various stability parameters, including gravity fluctuations, couple stress, anisotropy, and heat source. The results show that the mechanical anisotropy parameter and Vadasz number lead to system destabilization, while the couple stress parameter, Lewis number, gravity parameter, solute Rayleigh number, and thermal anisotropy parameter help to stabilize the system. Furthermore, the system is more stable with exponential gravity fluctuations and less stable with parabolic gravity fluctuations. This finding offers insights into thermal convective instability in porous media, impacting applications in geoscience, engineering, and environmental science.

Integrating Recycled and Alternative Materials in 3D Concrete Printing for Sustainable Development

3DCP changes the face of construction. It also increases design flexibility, independence from labor, and environmental sustainability. This paper presents research based on some 3DPCs replacing conventional materials with green concrete materials, including aggregates from waste, plastic and rubber materials, recycled glass, geopolymers, and supplementary cementitious materials. These materials reduce carbon emissions and resource depletion, with properties such as tensile strength and durability similar to or better than those of ordinary concrete. Several barriers still need to be overcome, such as material variability, while mechanical anisotropy, scalability constraints, and high equipment costs are other significant factors. For 3DPC to play its full role in achieving the goals of sustainable construction, these barriers should be reduced to a minimum by mixing design optimization, standardization processes, and innovative production techniques.

Effect of rod-like and flake-like additive particles on fracture mechanisms and mechanical anisotropy of sintered Nd-Fe-B magnets

The particles of different shapes, multi-walled carbon nanotubes (CNTs) and graphene nanosheets (GNs), were used to modulate the mechanical properties and anisotropy of the magnets. It is found that the rod-shaped CNTs can increase the bending strength ratio of the c and a axes of the magnet from 1.114 to 1.254, while flake-like GNs decrease it from 1.114 to 0.989. In-depth analysis indicates that the mechanical anisotropy of the magnet is greatly influenced by the distribution and thickness of the rare earth phase (RE phase), with the thicker RE phase demonstrating greater capability of blunting at the crack tip. Using the finite element method, it is found that the strength of brittle material can be enhanced by the additive particles owing to the inhibition of crack initiation and stress conduction, as well as the deflection of the crack. The flake-like GNs weaken the mechanical anisotropy of magnets by varying the distribution of RE phase and form a shell encompassing the main phase. Nonetheless, the alignment of CNTs occurring in the process of magnetic orientation process can significantly increase the mechanical anisotropy of the magnet. In particular, when loaded in the parallel c axis (c∥) direction, the cracks need to penetrate the main phase due to the strong frictional interlocking between CNTs and the main phase grains, in which case the bending strength will be significantly increased. By contrast, when loaded in the vertical c axis (c⊥) direction, the cracks can bypass the rod-like particles and change directions of propagation. As such, the increase in bending strength is smaller than that in loading along with the c∥ direction.

Cryogenic temperature tensile properties of laser powder bed fused Ti-6Al-4V

Unnotched and notched tensile properties of Ti-6Al-4V (Ti64) alloy, additively manufactured using the laser powder bed fusion (LPBF) technique, at cryogenic temperatures of 90, 77 and 20 K were investigated. The LPBF process parameter combination was chosen such that the investigated alloy has not only a minimum in porosity, but also an equiaxed prior β microstructure, which predominantly contains acicular α/α’ lath structure in basket-weave morphology, that results in a high strength and ductility combination as well as insignificant mechanical anisotropy at room temperature (300 K). Tensile tests revealed that the yield (σy) and tensile (σu) strengths of LPBF Ti64 are superior while elongation to failure (ef) is comparable to those of the conventionally manufactured (CM) Ti64 down to 77 K, owing to the fine α/α’ lath microstructure in the former. While the progressive reduction of <a>-basal and prismatic dislocation slip activity with decreasing deformation temperature enables a steep rise in σy, the unnotched specimens fractured catastrophically without macroscopic yielding at 20 K. Detailed postmortem analyses revealed the absence of significant twinning-based deformation in LPBF Ti64, in stark contrast to the CM ones at cryogenic temperatures. Instead, deformation kink bands with varying sizes and misorientation were found to be increasingly active within the prior β grains. A large misorientation at the kink band boundary within the β grain leads to void nucleation followed by crack growth, which eventually results in brittle failure at 20 K. While relatively notch insensitive from 300 to 77 K, LPBF Ti64 was notch brittle at 20 K. These results highlight the importance of the unique hierarchical micro- and meso-structural features of LPBF Ti64 on the tensile mechanical behavior, especially at cryogenic temperatures.

Modeling and analysis of the mechanical anisotropy of Hastelloy X alloy fabricated by laser powder bed fusion

Modeling and analysis of the mechanical anisotropy of Hastelloy X alloy fabricated by laser powder bed fusion

Effect of isothermal annealing on yield anisotropy of AZ31 Mg alloy bars processed by ambient extrusion

Magnesium and its alloys show strong mechanical anisotropy due to their hexagonal close-packed structure. This paper processed ambient extrusion and subsequent annealing on AZ31 magnesium alloy bars to investigate the effect of working hardening and texture weakening on yield anisotropy of magnesium alloy. After ambient extrusion, yield strength on different loading direction are improved due to working hardening. ED-yield strength has the highest increment because work hardening has a higher effect on prismatic slip. Then, yield anisotropy becomes stronger with the increase of extrusion train. During annealing, static recrystallization occurs firstly in {101‾1} twinning zones and producing recrystallized grains with random orientation. With the growth of recrystallized grains, basal fiber texture is weakened gradually. Such weak basal texture can promote the activation of basal slip when loading along ED, so ED-yield strength shows a high decrement. On this way, the yield anisotropy in AZ31 magnesium alloy bars is weakened through ambient extrusion and subsequent annealing.

Grain size hardening versus texture softening: Mechanical anisotropy of an AZ31B magnesium alloy processed by equal-channel angular pressing

Microstructural evolution of hexagonally close-packed (hcp) alloys subjected to severe plastic deformation differs from that of alloys with cubic crystal structure. While grain refinement is the main objective in conventional ECAP texture changes in hcp materials can result in lower strength but improved ductility depending on the deformation direction. This paper addresses the question of how the processes of grain size hardening and texture softening contribute to the highly anisotropic mechanical behavior of a severely deformed AZ31B magnesium alloy. ECAP is performed at different temperatures starting at 250 °C for the first 4 passes and subsequently reduced to 200 °C (C5, C6) and 150 °C (C7, C8). The mechanical properties of the resulting material conditions are investigated with tensile tests in four different deformation directions. While the yield strength increases up to 280 MPa in the transverse direction (TD), an opposite trend of low strength and good ductility can be observed for deformation in the extrusion (ED) and normal directions (ND). Additional microstructural investigations using EBSD show that the grain size is reduced by 95% during ECAP. Moreover, texture measurements using XRD reveal a strong fiber texture, with a high number of basal planes parallel to the shear plane of ECAP deformation, which results in a significantly improved ductility and lower strength in ED and ND. The results are discussed in the light of the competition between grain size hardening and texture softening. They highlight the potential of ECAP for the improvement of strength and ductility for magnesium alloys.

Fabrication and characterization of SiC-reinforced magnesium-matrix composites with honeycomb structures and anisotropic properties

This study presents a novel approach for fabricating SiC-reinforced magnesium matrix composites by combining digital light processing (DLP) with pressureless infiltration. Pre-oxidation of SiC powder enhanced its wettability with the magnesium alloy, enabling the near-net-shape fabrication of honeycomb Mg-based composites with precisely controlled SiC and Al2O3 powder ratios. The influence of varying ceramic content on the microstructure and compressive properties of the composites was investigated, revealing significant mechanical anisotropy. A combined approach utilizing fracture morphology analysis and finite element simulations elucidated the compressive behavior and failure mechanisms of the composites under different loading directions. This work not only offers a promising route for on-demand design and fabrication of Mg-based composites but also provides valuable insights into understanding the mechanical behavior of architected composites.

In-situ synchrotron high energy X-ray diffraction study on the deformation mechanisms of D019-α2 phase during high-temperature compression in a TiAl alloy

The α2 phase with an ordered hexagonal structure has a strong mechanical anisotropy. The limited plasticity interacting with crystallographic texture formation undoubtedly complicate the deformation mechanisms of the α2 phase. Taking advantage of in-situ synchrotron high energy X-ray diffraction (HEXRD), this study unveils the origin of the α2 texture and its correlation with plastic deformation. Upon loading at 800 °C, the dislocation glide in the γ phase initiates at a stress of 370 MPa and that in the α2 phase at a stress of 670 MPa. Nevertheless, the texture evolution of the α2 phase sets in in parallel with that of the γ phase, and these textures are preliminarily established at a stress of 650 MPa. A main <11 2‾ 0> fiber texture with the c axis of the α2 unit cell aligned vertically to the compression axis has been unexpectedly evolved. This texture forms primarily via rigid body rotation and is correlated with glide and twin activation in the neighboring γ phase. The preferential orientation primarily favors double prismatic glide in α2 and in addition triggers the tensile twin activation. The grain rotation caused by the tensile twin slightly affects the α2 transverse texture evolution. The results unveil a complex interaction between the α2 phase deformability, texture evolution and the combined elastic-plastic deformation of the phases γ and α2 in TiAl alloys.

Influence of Solution Treatment Temperatures on LPBF-Produced Inconel 939 Alloy on Mechanical Performance

This study investigates the influence of solution treatment temperatures on the microstructure and mechanical properties of LPBF (Laser Powder Bed Fusion)-manufactured Inconel 939 alloy. The primary objectives are to assess the impact of sub-recrystallization (below recrystallization temperature) and recrystallization temperatures during solution treatment on mechanical performance under different conditions. This study validates the hypothesis concerning carbide redistribution and mechanical performance in LPBF-produced Inconel 939 parts through comprehensive analysis, including microstructure studies and tensile tests. The results indicate that higher heat treatment temperatures lead to significant changes in carbide redistribution and mechanical performance. For instance, at room temperature, the specimen with sub-recrystallization solution treatment temperature exhibited superior mechanical properties compared to both the as-built and recrystallization-temperature solution treatment specimens. However, at elevated temperatures (700 °C), a reversal in mechanical anisotropy was observed, with the vertical axis demonstrating higher tensile strength compared to the horizontal axis for all material states. Furthermore, a microstructural analysis revealed distinct changes in grain structure and precipitate distribution, particularly the migration of carbides from grain boundaries to intragranular regions. These findings underscore the importance of precise control over heat treatment parameters to achieve optimal mechanical behavior. This research provides valuable insights into optimizing LPBF processes for the Inconel 939 alloy, highlighting the need for a meticulous control of the solution treatment parameters to ensure mechanical integrity. The findings contribute to a broader understanding of material-specific responses in additive manufacturing, with significant implications for aerospace applications.

Investigation on Microstructure and Mechanical Properties Anisotropy of Inconel625 Components Fabricated by Different Frequency Ultrasonic Vibration-Assisted CMT arc Additive Manufacturing

Investigation on Microstructure and Mechanical Properties Anisotropy of Inconel625 Components Fabricated by Different Frequency Ultrasonic Vibration-Assisted CMT arc Additive Manufacturing