Aluminum matrix composites reinforced with dispersed particles have attracted considerable attention due to their potential in various applications requiring a combination of high specific strength, rigidity, and wear resistance. In particular, the use of Al-Cu-Fe alloy as a reinforcing phase promises improved mechanical properties of the composite compared to monolithic aluminum.
The distribution of reinforcing particles plays a critical role in determining the mechanical properties of the composite. Optimum distribution implies uniform dispersion of Al-Cu-Fe particles in the aluminum matrix, avoiding agglomeration, which can lead to local stress concentrators. Composite production methods such as powder metallurgy or stir casting allow control over the morphology and distribution of reinforcing phases. Microstructure analysis using optical microscopy and scanning electron microscopy (SEM) is necessary to confirm the uniformity of distribution and to estimate the particle size.
The introduction of Al-Cu-Fe particles into the aluminum matrix has a significant effect on its mechanical properties. As a rule, an increase in the yield strength, tensile strength and elastic modulus is observed compared to pure aluminum. The strengthening mechanism is associated with the restriction of dislocation movement by reinforcing particles. The effectiveness of strengthening depends on the volume fraction of the reinforcing phase, its size and morphology. In addition, the presence of an interphase boundary between the Al-Cu-Fe particles and the aluminum matrix plays an important role in load transfer and preventing crack initiation. Tensile, compression and hardness tests allow us to evaluate the effect of reinforcement on the mechanical properties of the composite.
Using powder metallurgy, an innovative composite material was developed consisting of an aluminum matrix reinforced with 30% by volume Al-Cu-Fe quasi-crystalline particles obtained from elemental powders. Scanning electron microscopy analysis revealed that the key failure mechanism of the composite is cracking of the reinforcing elements oriented perpendicular to the applied load.
Due to the fine-grained structure of the matrix (grain diameter less than 10 μm), comparable sizes of reinforcing particles and their uniform distribution in the volume, the tensile strength and yield strength of the developed composite have increased significantly. In particular, for the composite made of commercially pure materials, these indicators have improved by 111% and 220% compared to similar characteristics of the matrix. For the composite version made of high-purity materials, the increase in tensile strength and yield strength was 201% and 328%, respectively.
The elastic modulus of both composite variants demonstrated values close to the theoretical upper limit calculated using the rule of mixtures. The high efficiency of the composite reinforcement is also explained by the reliable adhesion between the spherical reinforcing particles and the aluminum matrix, which is confirmed by the analysis of the fracture surface. Measurements of the diffusion layer at the aluminum/reinforcing material interface, performed using the Auger spectroscopy method, also indicate the high quality of the component connection.
Pure aluminum matrix composites reinforced with Al-Cu-Fe alloy particles represent a promising class of materials with improved mechanical properties. Careful control of the microstructure and optimization of reinforcement parameters are key factors to achieve the desired characteristics. Further research aimed at better understanding the deformation and failure mechanisms of these composites will open up new possibilities for their application in various industries.
Author: F. Tang, I. E. Anderson, S. B. Biner
Institute: Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA