Effect of ZrB2 particles on the microstructure and mechanical properties of hybrid (ZrB2 + Al3Zr)/AA5052 insitu composites

Present study outlines the effect of ZrB2 particles variation on the morphology and mechanical properties of (ZrB2+Al3Zr)/AA5052Al alloy composites. Composites with varying amount of ZrB2 particles have been produced by direct melt reaction (DMR) technique. These composites have been characterized by X-ray diffractometer (XRD) and energy-dispersive spectroscopy (EDS) to confirm the presence of ZrB2 and Al3Zr particles. Optical microscopy (OM) and scanning-electron microscopy (SEM) have been used to understand the morphology. To see the effect of ZrB2 variation on mechanical properties, hardness and tensile properties have been evaluated. The XRD and EDS results confirm the successful formation of ZrB2 particles in matrix of AA5052Al alloy. SEM and TEM studies exhibit that ZrB2 particles are mostly in hexagonal and some rectangular shape while Al3Zr particles are in polyhedron and rectangular shapes. Most of ZrB2 particles are within a size range of 10-190 nm. Interface region is free of any impurity. OM studies show grain refinement of AA5052Al alloy matrix with formation of second phase ZrB2 particles. Tensile results indicate that the UTS and YS improve up to 3 vol.% of ZrB2 but beyond this composition a decreasing trend is observed. The strength coefficient increases with increase in ZrB2 particles up to 3 vol.% in the Al3Zr/Al alloy composites, whereas strain hardening decreases. While beyond 3 vol.% ZrB2 particles in the Al3Zr/Al alloy composite, opposite trend is observed in strength coefficient and strain hardening. Percentage elongation also improves with 1vol.% ZrB2, but further addition of ZrB2 shows an adverse effect. However, a continuous increasing trend has been observed in bulk hardness. Fracture studies show facets of Al3Zr particles and dimples of matrix, but with inclusion of ZrB2 dimple size decreases. Increase in ZrB2 leads to quasi cleavage fracture and debonding of ZrB2 clusters. (C) 2015 Elsevier B.V. All rights reserved.