Tailorable Mechanical Properties Research Articles

Fibrin-Dextran Hydrogels with Tunable Porosity and Mechanical Properties.

Hydrogels as scaffolds in tissue engineering have gained increasing attention in recent years. Natural hydrogels, e.g., collagen or fibrin, are limited by their weak mechanical properties and fast degradation, whereas synthetic hydrogels face issues with biocompatibility and biodegradation. Therefore, combining natural and synthetic polymers to design hydrogels with tunable mechanical stability and cell affinity for biomedical applications is of interest. By using fibrin with its excellent cell compatibility and dextran with controllable mechanical properties, a novel bio-based hydrogel can be formed. Here, we synthesized fibrin and dextran-methacrylate (MA)-based hydrogels with tailorable mechanical properties, controllable degradation, variable pore sizes, and ability to support cell proliferation. The hydrogels are formed through in situ gelation of fibrinogen and dextran-MA with thrombin and dithiothreitol. Swelling and nuclear magnetic resonance diffusometry measurements showed that the water uptake and mesh sizes of fabricated hydrogels decrease with increasing dextran-MA concentrations. Cell viability tests confirm that these hydrogels exhibit no cytotoxic effect.

Experimental investigations into the dynamic response of sandwich panels with multi-layered corrugated cores subjected to underwater impulsive load

Sandwich panels with multi-layered core have attractive performance due to the excellent designability and tailorable mechanical properties. In present study, the dynamic responses of the sandwich panels with multi-layered corrugated core were investigated experimentally under underwater impulsive loads. In order to exploit the potential for performance improvement, some attempts have been made by designing core configuration from several aspects including stack orientation, layer number, core gradation and core topology. Experimental results indicate that the core in the cross-stacked would deteriorate back face deflection. The core with three layers performed best in constraint back face deflection because of the well balance between energy absorption and residual flexural stiffness. The core gradation in wall thickness would reduce back face deflection, while the one in corrugation angle would increase back face deflection. The core topology designed into reentrant trapezoidal corrugation behaved effectively in inhabiting back face deformation due to the periodic progressive collapse mechanism of core webs.

Novel bridge assistance strategy for tailoring crosslinking networks within soybean-meal-based biocomposites to balance mechanical and biodegradation properties

The cost-effective fabrication of environmentally friendly soybean meal (SM)-based biocomposites with tailorable biodegradability, mechanical properties, and water resistance remains a challenge. Herein, a novel bridge assistance strategy to effectively balance the performance of SM-based biocomposites was designed by constructing multiple tailorable networks using diethylenetriamine (DETA), melamine-urea-glyoxal (MUG), and polyamidoamine-epichlorohydrin (PAE) resins. The Schiff’s base reaction between DETA and MUG yielded a more reactive, branched DETA@MUG crosslinker, which could efficiently form co-crosslinks with long-chained PAE. Owing to the stronger bridge interactions of DETA, the obtained PAE/DETA@MUG co-crosslinks were more stable than those formed using PAE and MUG alone. Consequently, the PAE/DETA@MUG co-crosslinker system effectively reinforced the multiple networks and the performance of the SM-based biocomposites via the formation of more DETA@MUG–protein, PAE–protein, PAE–carbohydrate, and PAE–wood crosslinks, resulting in improvements in the dry tensile strength (158.2%) and water resistance (461.9%). Moreover, the multiple networks formed by branched DETA@MUG were beneficial for balancing the interior forces of the obtained SM-based resin, thereby improving its toughness by 64.3%. The DETA bridge also decreased the numbers of stable PAE–wood and PAE–SM bonds in the SM-based biocomposites while ensuring the necessary PAE/DETA@MUG co-crosslinks, which improved the biodegradation rate by 16.2% without compromising the mechanical properties and water resistance. Therefore, this bridge assistance strategy is highly suited for the commercial production of SM-based polymers and biocomposites with balanced mechanical properties, water resistance, and biodegradability.

Evaluation of the Immune Response to Chitosan-graft-poly(caprolactone) Biopolymer Scaffolds.

Biomimetic scaffolds recreating key elements of the architecture and biological activity of the extracellular matrix have enormous potential for soft tissue engineering applications. Combining appropriate mechanical properties with select biological cues presents a challenge for bioengineering, as natural materials are most bioactive but can lack mechanical integrity, while synthetic polymers have strength but are often biologically inert. Blends of synthetic and natural materials, aiming to combine the benefits of each, have shown promise but inherently require a compromise, diluting down favorable properties in each polymer to accommodate the other. Here, we electrospun a material comprising chitosan, a natural polysaccharide, and polycaprolactone (PCL), one of the most widely studied synthetic polymers used in materials engineering. In contrast to a classical blend, here PCL was chemically grafted onto the chitosan backbone to create chitosan-graft-polycaprolactone (CS-g-PCL) and then combined further with unmodified PCL to generate scaffolds with discreet chitosan functionalization. These small amounts of chitosan led to significant changes in scaffold architecture and surface chemistry, reducing the fiber diameter, pore size, and hydrophobicity. Interestingly, all CS-g-PCL-containing blends were stronger than control PCL, though with reduced elongation. In in vitro assessments, increasing the CS-g-PCL content led to significant improvements in in vitro blood compatibility compared to PCL alone while increasing fibroblast attachment and proliferation. In a mouse subcutaneous implantation model, a higher CS-g-PCL content improved the immune response to the implants. Macrophages in tissues surrounding CS-g-PCL scaffolds decreased proportionately to the chitosan content by up to 65%, with a corresponding decrease in pro-inflammatory cytokines. These results suggest that CS-g-PCL is a promising hybrid material comprising natural and synthetic polymers with tailorable mechanical and biological properties, justifying further development and in vivo evaluation.

Lignin nanoparticle-enhanced biobased resins for digital light processing 3D printing: Towards high resolution and tunable mechanical properties

The more widespread applicability of photopolymerization-based three-dimensional (3D) printing is limited by the availability of light-curable resins, most of which are based on fossil-derived compounds. We developed a biobased lignin-derivable resin by utilizing methacrylated derivatives of vanillin, vanillyl alcohol, and eugenol as aromatic monomers. Lignin nanoparticles (LNPs) were incorporated as functional fillers that enhance print resolution and material properties. The crosslinking degree, and thereby the tensile properties, was modulated through the use of mono- or dimethacrylated vanillin derivatives in the resin formulation. The LNPs acted as UV absorbers, conferring better control of the photopolymerization process by preventing light penetration across unintended layers, leading to enhanced print resolution. The LNPs showed excellent dispersion stability due to their size and morphology. The inclusion of up to 2 wt% of LNPs improved the ductility of the 3D printed nanocomposites through toughening mechanisms enabled by the rigid nanoparticles. Finally, exploiting the differences in crosslinking degree of the resin formulations, a multi-material model featuring both soft and rigid domains was fabricated. This study demonstrates a simple but effective strategy for the design of biobased photocurable resins with tailorable mechanical properties that are suitable for high-resolution and multi-material 3D printing.

Tough Epoxy Vitrimer with Hybrid Networks and Its Applications in Reprocessable Composites

Progress in the ever‐growing vitrimer chemistry opens up great opportunities for a sustainable society by producing reprocessable thermosets. However, most vitrimers suffer from the conflict between mechanical performance and dynamic reactivity, hindering the development of industrial applications. Herein, a facile but universal material design strategy is proposed to yield tough epoxy vitrimers while preserving excellent reprocessability. Copolymerization and bond exchange reactions can build covalent bridges between heterogeneous polymer networks, thus leading to a hybrid dynamic covalent polymer network containing hard and soft segments. Tailorable mechanical and thermal properties are obtained by controlling the ratio of hard‐to‐soft components. The resulting epoxy vitrimer can balance strength and stretchability while exhibiting brittle‐to‐ductile transformation in tensile tests. Enhanced fracture toughness is achieved compared to both pristine hard and soft vitrimers. The resulting vitrimers exhibit excellent processability and potential applications in composite fabrication, welding and reshaping, and multiple shape memory functions. This work presents a feasible approach to satisfying the demands of mechanical performance and dynamic reactivity in the design of epoxy vitrimers. The material design principle will be applicable to a wide range of vitrimer systems to pursue desirable properties.

Synthesis and characterization of high entropy carbide-MAX two-phase composites

In the present work, the formation of high entropy MAX phase during mechanical alloying and subsequent spark plasma sintering (SPS) of two powder mixtures with (HfZrNbTiTa)3SiC2 and (HfZrNbTiTa)3(SiAl)1.1C1.95 stoichiometries is investigated. The results indicate that a high entropy carbide (HEC) with cubic HfC-prototype structure is formed for both compositions after 7 h of mechanical alloying. The microstructural observations indicate the nano-sized nature of the as-milled powders. For both specimens, consolidation at high temperatures leads to a phase transition from single HEC to HEC-MAX complex. Ultrahigh microhardness values of 11 ± 2 GPa and 8 ± 2 GPa were obtained for the consolidated (HfZrNbTiTa)3SiC2 and (HfZrNbTiTa)3(SiAl)1.1C1.95 specimens, respectively. The results also revealed that the (HfZrNbTiTa)3(SiAl)1.1C1.95 exhibits ferromagnetic behavior with low magnetization saturation of only 1.709 emu/g, while (HfZrNbTiTa)3SiC2 shows a ferromagnetic behavior with relatively low coercivity and magnetization saturation. Finally, the findings provide a new route to tailor mechanical properties of HEC-MAX complexes by controlling the evolution of MAX phase.

Lyotropic liquid crystal elastomers for drug delivery

Silicone elastomers like polydimethylsiloxane (PDMS) possess a combination of attractive material and biological properties motivating their widespread use in biomedical applications. Development of elastomers with capacity to deliver active therapeutic substances in the form of drugs is of particular interest to produce medical devices with added functionality. In this work, silicone-based lyotropic liquid crystal elastomers with drug-eluting functionality were developed using PDMS and triblock copolymer (diacrylated Pluronic F127, DA-F127). Various ternary PDMS–DA-F127–H2O compositions were explored and evaluated. Three compositions were found to have specific properties of interest and were further investigated for their nanostructure, mechanical properties, water retention capacity, and morphology. The ability of the elastomers to encapsulate and release polar and nonpolar substances was demonstrated using vancomycin and ibuprofen as model drugs. It was shown that the materials could deliver both types of drugs with a sustained release profile for up to 6 and 5 days for vancomycin and ibuprofen, respectively. This works demonstrates a lyotropic liquid crystal, silicone-based elastomer with tailorable mechanical properties, water retention capacity and ability to host and release polar and nonpolar active substances.

Synergistic effect of aramid and basalt fibers on mechanical, thermal and dynamic properties of polylactide hybrid composites

Today's market is looking for materials that have high-strength properties and are biobased at the same time. This manuscript demonstrates the possibility of reinforcing polylactide (PLA) through the incorporation of two types of fibers to produce high-performance composites. PLA composites reinforced with aramid (AF) and basalt fibers (BF) were produced by injection molding (10 wt%, 15 wt% and 20 wt%). Manufactured materials have undergone extensive analysis including mechanical, thermal, thermodynamic and structural studies. The increase of the fiber content resulted in significantly improved mechanical properties of the materials. Composites with 20 wt% of the fibers exhibited an increase in Young's modulus of ∼160%, and improved tensile strength by 30% compared to neat PLA. Moreover, the results indicated that each type of fiber was responsible for enhancing specific mechanical properties. AF improved Young's modulus such that for composites containing only 10 wt% of this fiber, Young's modulus increased by ∼100%, while the same content of BF alone increased Young's modulus by 43%. In the case of tensile strength, composites with BF exhibited higher values than seen for AF with improvement of 19% compared to the case of AF where only 3% improvement was seen compared to PLA. Statistical analysis revealed that the additives had a significant impact on the change of both physical and mechanical properties.The thermomechanical tests followed a similar trend as the mechanical ones, such that a higher content of the filler caused an increase in the storage modulus. The simultaneous addition of AF and BF resulted in the same increase in the stiffness of the composites as the addition of the same weight value of expensive aramid fibers. The addition of fibers has not however changed the characteristic temperatures obtained during differential scanning calorimetry.The work presents the possibility of creating hybrid materials with tailorable mechanical and structural properties. We demonstrate that with different fibers it is possible to tune properties of polymeric composites and make them suitable for specific applications.

Design of isotropic 2D chiral metamaterials based on monohedral pentagonal tessellations

A novel class of transversely-isotropic metamaterials with the potential to exhibit a wide range of Poisson’s ratios and stiffnesses is proposed in this work. These metamaterials, which also have the potential to exhibit auxetic behaviour, are formed through the chiralisation of 2D monohedral Euclidean pentagonal tessellations. Through Finite Element simulations and experimental testing on additively manufactured prototypes, we show that these systems can exhibit Poisson’s ratios which encompass the entire range of transverse isotropicity, i.e. +1 to -1, and that the mechanical properties of these structures can be tailored considerably through variation of the geometric parameters without a loss of global symmetry and isotropy. The level of versatility observed in these new metamaterials exceeds by far that which is commonly found in traditional and well-known isotropic auxetic systems such as hexachiral honeycombs. In addition, analytical expressions pertaining to the geometric limits which define the realisability of this new class of auxetic metamaterials have also been derived and presented. The findings of this work demonstrate that pentagonal tessellations have considerable potential for the development of novel metamaterials and that the geometric constraints associated with transverse isotropy need not necessarily be an insurmountable barrier for the design of metamaterials with tailorable and versatile mechanical properties.

Accelerating matrix/boundary precipitations to explore high-strength and high-ductile Co34Cr32Ni27Al3.5Ti3.5 multicomponent alloys through hot extrusion and annealing

• Hot extrusion reduces grain sizes and simultaneously accelerates precipitation. • Pre-existing dislocation slips and hierarchical precipitates cause high strength. • Interaction among dislocations, stacking faults, and twins ensures acceptable ductility. Annealing-regulated precipitation strengthening combined with cold-working is one of the most efficient strategies for resolving the conflict between strength and ductility in metals and alloys. However, precipitation control and grain refinement are mutually contradictory due to the excellent phase stability of multicomponent alloys. This work utilizes the high-temperature extrusion and annealing to optimize the microstructures and mechanical properties of the Co 34 Cr 32 Ni 27 Al 3.5 Ti 3.5 multicomponent alloy. Hot extrusion effectively reduces grain sizes and simultaneously accelerates the precipitation of coherent L1 2 nanoparticles inside the face-centered cubic (FCC) matrix and grain boundary precipitations (i.e., submicron Cr-rich particles and L1 2 -Ni 3 (Ti, Al) precipitates), resulting in strongly reciprocal interaction between dislocation slip and hierarchical-scale precipitates. Subsequent annealing regulates grain sizes, dislocations, twins, and precipitates, further allowing to tailor mechanical properties. The high yield strength is attributed to the coupled precipitation strengthening effects from nanoscale coherent L1 2 particles inside grains and submicron grain boundary precipitates under the support of pre-existing dislocations. The excellent ductility results from the synergistic activation of dislocations, stacking faults, and twins during plastic deformation. The present study provides a promising approach for regulating microstructures, especially defects, and enhancing the mechanical properties of multicomponent alloys.

Prediction and Validation of Flow Properties in Porous Lattice Structures

Abstract High-porosity metal foams have been extensively studied as an attractive candidate for efficient and compact heat exchanger design. With the advancements in additive manufacturing, such foams can be manufactured with controlled topology to yield highly tailorable mechanical and transport properties. In this study, a lattice Boltzmann method (LBM)-based pore-scale model is implemented to simulate the fluid flow in additively manufactured (AM) metal foams with unit cell topologies of Cube, Face Diagonal (FD)-Cube, Tetrakaidecahedron (TKD), and Octet lattices. The pressure gradient versus average velocity profiles predicted by the LBM model were validated against in-house measurements on the AM lattice samples with the same unit cell topologies. Based on the simulation results, a novel hybrid model is proposed to accurately predict the volume averaged flow properties (permeability and inertial coefficients) of the four structures. Specifically, the linear LBM (neglecting inertial forces) is first implemented to obtain the intrinsic permeability, and then the standard LBM is applied to obtain the inertial coefficient. Convenient correlations for those flow properties as a function of porosity and fiber diameter are constructed. The effects of the AM print qualities on the flow properties are also discussed. The advantages of the hybrid model compared to the polynomial fitting approach for determining flow properties are discussed and compared quantitatively. The hybrid model and presented results are valuable for flow and thermal transport evaluation when designing new metal foams for specific applications and with different materials and topologies. The presented correlations based on pore-scale simulations can also be conveniently used in volume-averaged models to predict the macroscale flow behavior in such complex structures.

Fire testing and mechanical properties of neat and elastomeric polylactic acid composites reinforced with raw and enzymatically treated hemp fibers

ABSTRACT A new class of biobased composites with tailorable mechanical properties made of natural fibers, polylactic acid, and ferulic acid derivatives (FAD) is studied. FAD was used to develop composites with elastomeric properties like improved elongation at break and highly reversible deformation upon elongation. Composites were prepared using raw and enzymatically treated hemp fibers. The fibers were defibrillated due to the enzymatic treatment increasing their aspect ratio. The composites were characterized by their mechanical properties and their reaction to fire. No significant change in the dispersion of the fibers in the composites was reported. Homogenously dispersed crystallites of FAD were observed by scanning electron microscopy in the PLA matrix and at the interface between the PLA and the fibers, where they are suspected to increase the free volume in correlation with a decrease in mechanical properties following the increase in the aspect ratio of the fibers. FAD also degraded the reaction to fire of the material with an increase in 10% of the peak of Heat Release Rate (pHRR) in comparison to neat PLA. It also increased the charring residue up to 3 wt.%. A synergistic effect between FAD and the lignin increasing the charring residue is also reported.

Development and optimization of an ocular hydrogel adhesive patch using definitive screening design (DSD).

Adhesive hydrogels based on chemically modified photocrosslinkable polymers with specific physicochemical properties are frequently utilized for sealing wounds or incisions. These adhesive hydrogels offer tunable characteristics such as tailorable tissue adhesion, mechanical properties, swelling ratios, and enzymatic degradability. In this study, we developed and optimized a photocrosslinkable adhesive patch, GelPatch, with high burst pressure, minimal swelling, and specific mechanical properties for application as an ocular (sclera and subconjunctival) tissue adhesive. To achieve this, we formulated a series of hydrogel patches composed of different polymers with various levels of methacrylation, molecular weights, and hydrophobic/hydrophilic properties. A computerized multifactorial definitive screening design (DSD) analysis was performed to identify the most prominent components impacting critical response parameters such as adhesion, swelling ratio, elastic modulus, and second order interactions between applied components. These parameters were mathematically processed to generate a predictive model that identifies the linear and non-linear correlations between these factors. In conclusion, an optimized formulation of GelPatch was selected based on two modified polymers: gelatin methacryloyl (GelMA) and glycidyl methacrylated hyaluronic acid (HAGM). The ex vivo results confirmed adhesion and retention of the optimized hydrogel subconjunctivally and on the sclera for up to 4 days. The developed formulation has potential to be used as an ocular sealant for quick repair of laceration type ocular injuries.

TPMS-based interpenetrating lattice structures: Design, mechanical properties and multiscale optimization

Compared to single-phase structures, interpenetrating lattice structures display the potential to achieve a wide range of tailorable physical and mechanical properties. Herein, we present a novel class of interpenetrating lattice structures based on triply periodic minimal surfaces. Using representative volume elements applied with the periodic boundary conditions, the contributions of the volume fraction and the interpenetrating parameter, a measure of the ratio of the two phases, on the mechanical properties and deformation behavior of the interpenetrating lattice structures are investigated. Results show that the mechanical properties are highly dependent on the interpenetrating parameter, and isotropic elasticity can be achieved at a particular value. Moreover, the uniaxial and shear deformation mechanisms (bending or stretching behavior) can be easily changed by adjusting the interpenetrating parameter. Our new interpenetrating lattice designs are experimentally validated using 3D-printed samples. Finally, a new multiscale optimization framework, based on simultaneously optimizing the distribution of the volume fraction and the interpenetrating parameter, is developed. Compared to the traditional optimized designs that only consider the volume fraction, the proposed optimized design reduces the structural compliance by more than 10.85%, confirming the effectiveness of the proposed optimization framework for lightweight applications.

Improved lightweight corrugated network design to auxetic perforated metamaterial

Auxetic metamaterials with peanut-shaped perforations are superior for durable morphing control applications due to its extremely low stress concentration level and controllable auxetic capability. However, there are some issues to be concerned for such metamaterials with complex cellular features, including (1) improving structure topology for higher material efficiency, (2) tunable Poisson's ratio from positive to negative, (3) characterization of full elastic properties. To this end, an improved lightweight design with orthogonal corrugated beams is proposed in this study to approximate the perforated auxetic structure and then its full anisotropic elastic constants are characterized by a distinctive computational homogenization model based on the eigenfunction expansion variational theory with simple implementation technique of periodic displacement constraints. The numerical model is verified by the experimental tests of three specimens with different geometrical topologies. Subsequently, the dependence of structural elastic responses on the microstructural configuration is highlighted towards an elevated understanding of cell-structure-property relationship. It is demonstrated that the local in-plane rotation of interconnected regions in unit cell under uniaxial loading contributes to the structural auxetic behavior. Also, it is feasible to achieve tailorable mechanical properties through flexible microstructural adjustment and a design criterion of the crucial zero Poisson's ratio is given by a polynomial in terms of the normalized amplitude and thickness of the curved beam. The results pave a way to the design and analysis of novel metamaterials with tunable mechanical properties.

Closed-loop chemical recycling of cross-linked polymeric materials based on reversible amidation chemistry

Closed-loop chemical recycling provides a solution to the end-of-use problem of synthetic polymers. However, it remains a major challenge to design dynamic bonds, capable of effective bonding and reversible cleaving, for preparing chemically recyclable cross-linked polymers. Herein, we report a dynamic maleic acid tertiary amide bond based upon reversible amidation reaction between maleic anhydrides and secondary amines. This dynamic bond allows for the construction of polymer networks with tailorable and robust mechanical properties, covering strong elastomers with a tensile strength of 22.3 MPa and rigid plastics with a yield strength of 38.3 MPa. Impressively, these robust polymeric materials can be completely depolymerized in an acidic aqueous solution at ambient temperature, leading to efficient monomer recovery with >94% separation yields. Meanwhile, the recovered monomers can be used to remanufacture cross-linked polymeric materials without losing their original mechanical performance. This work unveils a general approach to design polymer networks with tunable mechanical performance and closed-loop recyclability, which will open a new avenue for sustainable polymeric materials.

Digital light 3D printing of a polymer composite featuring robustness, self-healing, recyclability and tailorable mechanical properties

Producing lightweight structures with high weight-specific strength and stiffness, self-healing abilities, and recyclability, is highly attractive for engineering applications such as aerospace, biomedical devices, and smart robots. Most self-healing polymer systems used to date for mechanical components lack 3D printability and satisfactory load-bearing capacity. Here, we report a new self-healable polymer composite for Digital Light Processing 3D Printing, by combining two monomers with distinct mechanical characteristics. It shows a desirable and superior combination of properties among 3D printable self-healing polymers, with tensile strength and elastic modulus up to 49 MPa and 810 MPa, respectively. Benefiting from dual dynamic bonds between the linear chains, a healing efficiency of above 80% is achieved after heating at a mild temperature of 60 °C without additional solvents. Printed objects are also endowed with multi-materials assembly and recycling capabilities, allowing robotic components to be easily reassembled or recycled after failure. Mechanical properties and deformation behaviour of printed composites and lattices can be tuned significantly to suit various practical applications by altering formulation. Lattice structures with three different architectures were printed and tested in compression: honeycomb, re-entrant, and chiral. They can regain their structural integrity and stiffness after damage, which is of great value for robotic applications. This study extends the performance space of composites, providing a pathway to design printable architected materials with simultaneous mechanical robustness/healability, efficient recoverability, and recyclability.

Cooling rate as a process parameter in advanced roll forming to tailor microstructure, mechanical and corrosion properties of EN AW 7075 tubes

AbstractThe effects of solution heat treatment parameters and quench media as a processing tool for tailoring microstructure, mechanical and corrosion properties in roll forming of EN AW 7075 alloy were studied. The highest yield stress and ultimate tensile strength were obtained for the specimens quenched in water, while the air‐cooled specimens exhibited inferior mechanical properties. Microstructural analysis of specimens showed that except water‐quenched specimens, the parts cooled/quenched in oil, in direct contact with tool steel and air are characterized by coarse precipitates and precipitate‐free zones. The corrosion tests showed that the cooling rate has a pronounced influence on the corrosion resistance and related mechanism of EN AW 7075 alloy. The surfaces of specimens quenched in water remained intact although pitting corrosion took place. The microstructure of the part processed by roll forming was explored in direct comparison. It is revealed that by the employment of quenching nozzles, a high cooling rate similar to the water‐quenched condition can be achieved. Results obtained in the present study pave the way to directly tailor aluminum parts for specific applications.

Effects of Minor Gadolinium Addition and T4 Heat Treatment on Microstructure and Properties of Magnesium

Mg–Gd alloys are candidates for degradable implants combining favorable mechanical and corrosion properties. Gd has a high solid solubility in Mg and an acceptable biocompatibility. The influences of different amount of Gd additions and solid solution (T4) treatment on mechanical properties and corrosion in 0.9 wt% NaCl and cell culture medium (CCM) of magnesium are systematically investigated. The effects of Gd are clarified by microstructural characterizations as well as stress and degradation analysis. It is shown that minor Gd additions to pure Mg lead to Gd solid solution in Mg (α) and the formation of Mg5Gd intermetallic particles (IMPs), which increase the hardness, tensile, and compressive strength. The GdH2 phase is found in low‐alloyed Mg–Gd alloys. The corrosion rate (CR) is increased by the addition of more Gd due to the increased kinetics of the cathodic reaction. However, the resistance to degradation is effectively improved by T4 heat treatment due to the dissolution of IMPs. The reduced susceptibility to pitting can be achieved by a minor Gd addition and T4 heat treatment. The Mg–2Gd alloy is a potential candidate for implants due to its good combination of tailorable mechanical properties and low homogeneous in vitro degradation rate (DR).