A combined experimental-numerical approach for determining mechanical properties of aluminum subjects to nanoindentation

A Concentrated AlCl3-Diglyme Electrolyte for Hard and Corrosion-Resistant Aluminum Electrodeposits

A concentrated aluminum chloride (AlCl₃)-diglyme (G2) electrolyte is used to prepare hard and corrosion-resistant aluminum (Al) electrodeposited films. The Al electrodeposits obtained from the electrolyte with an AlCl₃/G2 molar ratio x = 0.4 showed a void-free microstructure composed of spherical particles, in stark contrast to flake-like morphologies with micro-voids for lower x. Neutral complexes rarely exist in the x = 0.4 electrolyte, resulting in a relatively high conductivity despite the high concentration and high viscosity. Nanoindentation measurements for the Al deposits with >99% purity revealed that the nanohardness was 2.86 GPa, three times higher than that for Al materials produced through electrodeposition from a well-known ionic liquid bath or through severe plastic deformation. Additionally, the void-free Al deposits had a <100> preferential crystal orientation, which accounted for better resistance to free corrosion and pitting corrosion. Discussions about the compact microstructure and <100> crystal orientation of deposits obtained only from the x = 0.4 concentrated electrolyte are also presented.

Nanoindentation of Aluminum Single Crystals: Experimental Study on Influencing Factors

Results from nanoindentation of aluminum single crystals deliver valuable information as model systems for understanding technical aluminum alloys. The effect of the crystal orientation and the azimuthal indenter orientation on indentation hardness and modulus was studied by Vickers indentation (max. load 10 mN) on single crystal surfaces with (100), (110), and (111) orientations. The average indentation hardness varied, depending on the crystallographic orientation, by 1.8%. The anisotropy of the elastic modulus (1.1% of the average modulus) is lowered (indentation averaging effect). This is predicted by explicit approximation of the contact problem (conical indenter, orthotropic material). It was found that indentation hardness and modulus vary periodically with the azimuthal indenter orientation on (100)- and (110)-oriented surfaces (relative amplitude of 1.8% for indentation hardness and 2.6% of the modulus). This is attributed to the combined effect of the indenter geometry and crystal symmetry. For the first time, this effect was quantified for aluminum single crystals.

Assessment of Nano-Indentation Method in Mechanical Characterization of Heterogeneous Nanocomposite Materials Using Experimental and Computational Approaches

This study investigates the capacity of the nano-indentation method in the mechanical characterization of a heterogeneous dental restorative nanocomposite using experimental and computational approaches. In this respect, Filtek Z350 XT was selected as a nano-particle reinforced polymer nanocomposite with a specific range of the particle size (50 nm to 4 µm), within the range of indenter contact area of the nano-indentation experiment. A Sufficient number of nano-indentation tests were performed in various locations of the nanocomposite to extract the hardness and elastic modulus properties. A hybrid computational-experimental approach was developed to examine the extracted properties by linking the internal behaviour and the global response of the nanocomposite. In the computational part, several representative models of the nanocomposite were created in a finite element environment to simulate the mechanism of elastic-plastic deformation of the nanocomposite under Berkovich indenter. Dispersed values of hardness and elastic modulus were obtained through the experiment with 26.8 and 48.5 percent average errors, respectively, in comparison to the nanocomposite properties, respectively. A disordered shape was predicted for plastic deformation of the equilateral indentation mark, representing the interaction of the particles and matrix, which caused the experiment results reflect the local behaviour of the nanocomposite instead of the real material properties.

Unusually high ratio of shear modulus to Young's modulus in a nano-structured gyroid metamaterial

Unlike the constant nature of elastic coefficients of isotropic bulk materials, the Young's (E) and shear (μ) moduli of nano-structured (NS) gyroid metamaterials change with relative density (ρ), but at different rates depending on the cell size of the structure. These elastic behaviors displayed by E and μ cause crossover/inversion of these two moduli, such that μ of the NS gyroid metamaterials is greater than E for the structures with ρ < 0.23. This peculiar elastic behavior causes NS gyroid metamaterials to display high μ/E values (~1.0), which are more than 250% larger than the typical values of the bulk material (~0.38), indicating that the NS gyroid metamaterial, even if it is light, is resistant to shear deformation. Here, we report the results of molecular dynamics simulations performed to elucidate the reason for unusually high μ/E values in NS gyroid metamaterials.

Can hyperelastic material parameters be uniquely determined from indentation experiments?

Uniqueness of hyperelastic parameters depends on a simple criterion: whether dimensionless material parameters are coupled with indentation displacement.