As a relatively new class of materials that exhibits a gradual compositional or microstructural change along one axis, functionally graded materials (FGM) emerged. As a result of this change, properties of the material also vary. This property change can be controlled by tailoring the composition or microstructure of the individual stacks in the FGM.
In the present study, aluminum matrix functionally graded composite materials with increasing amounts of B4C particles in an aluminum matrix were formed. The functionally graded materials were composed of 4 composite stacks with different compositions; namely, 0, 10, 20 and 30 volume % B4C particles. The matrix material was aluminum – 4 wt.% copper alloy. Preparation of the functionally graded materials was conducted through powder metallurgical methods including mixing, cold pressing and sintering without pressure. Samples were produced in dimensions according to 3-point bending standards.
Microstructure of the functionally graded materials contained some porosity, amount of which was seen to increase with increasing B4C reinforcement amount. All the stacks were subjected to Vickers microhardness measurements and it was seen that the hardness of the layers increased significantly with increasing reinforcement amount. The unreinforced layer had a hardness of 55 HV0.1 and that of the layer containing 30 % B4C was 143 HV0.1. On the other hand, the bending strength of the functionally graded material was seen to be lower than that of the unreinforced sample.
- Sobczak J., Drenchev LB., Metal Based Functionally Graded Materials, Bentham Books, 2009.
- Radhika N., Raghu R., Development of functionally graded aluminium composites using centrifugal casting and influence of reinforcements on mechanical and wear properties, Trans. Nonferrous Met. Soc. China 26 (2016) 905−916.
- Rajan TPD., Pillai RM., Pai BC. Characterization of centrifugal cast functionally graded aluminum-silicon carbide metal matrix composites, Mater. Char. 61 (2010) 923 – 928.
- Erdemir F., Canakci A., Varol T. Microstructural characterization and mechanical properties of functionally graded Al2024/SiC composites prepared by powder metallurgy techniques, Trans. Nonferrous Met. Soc. China 25 (2015) 3569−3577.
- ASTM B528 standard entitled: Standard Test Method for Transverse Rupture Strength of Metal Powder Specimens.