Characterization of Titanium Metal Matrix Composites (Ti-MMC) Made Using Different Manufacturing Routes

The mechanical and morphological properties of the unidirectional metal matrix composite (MMC) in titanium alloy reinforced with continuous silicon carbide (SiC) fibres are investigated. The lay-up manufacturing process known as the Foil / Fibre (FF) lay-up was compared with the matrix-coated-fibre (CF) method which promises a better final shape of the reinforcing fibre net. Tensile tests were performed to measure mechanical performance of the manufactured MMCs both longitudinally and transversely respect to the direction of SiC fibres. Elastic behaviour of the investigated MMCs was assumed orthotropic and related to mechanical properties and spatial distribution of the MMC constituents: SiC fibres and Titanium (Ti) matrix. This was achieved using micromechanical modelling based on Finite Element (FE) calculations. FE micromechanical modelling was carried out on the Representative Elementary Volume (REV) of the MMC microstructure resolved by non-destructive analysis such as X-Ray tomography. The analysis carried out highlighted and justified mechanical performance difference between composite laminates containing the same amount of SiC reinforcement fibres for unit of volume but made following different manufacturing routes. To compute overall orthotropic behaviour of the MMC laminate, each constituent was assumed as an elastic isotropic heterogeneity during the averaging. This simplify assumption was validated by comparison with experimental data during the mechanical characterization of the investigated MMC composites.

Deformation and Damage Assessments of Two DP1000 Steels Using a Micromechanical Modelling Method

Damage characterization and micromechanical modelling in dual-phase (DP) steels have recently drawn attention, since any changes in the alloying elements or process route strongly influence the microstructural features, deformation behavior of the phases, and damage to the micro-mechanisms, and subsequently the particular mechanical properties of the material. This approach can be used to stablish microstructure–properties relationships. For instance, the effects of local damage from shear cutting on edge crack sensitivity in the following deformation process can be studied. This work evaluated the deformation and damage behaviors of two DP1000 steels using a microstructure-based approach to estimate the edge cracking resistance. Phase fraction, grain size, phase distribution, and texture were analyzed using electron backscatter diffraction and secondary electron detectors of a scanning electron microscope and employed in 3D representative volume elements. The deformation behavior of the ferrite phase was defined using a crystal plasticity model, which was calibrated through nanoindentation tests. Various loading conditions, including uniaxial tension, equi-biaxial tension, plane strain tension, and shearing, along with the maximum shear stress criterion were applied to investigate the damage initiation and describe the edge cracking sensitivity of the studied steels. The results revealed that a homogenous microstructure leads to homogenous stress–strain partitioning, delayed damage initiation, and high edge cracking resistance.