Abstract
Al2O3-Ni-P composite powders with Ni-P contents of 10.9, 14.4, and 20.4 wt.% were synthesized via the Ni-P electroless deposition process. The as-received Al2O3-Ni-P composite powders were composed of Ni-P particles and Ni-P coating layer. Some Ni-P particles randomly adhered to the Al2O3powders, and their particle diameter ranged from 5 nm to 20 nm. The thin Ni-P layer had about 5 nm thick amorphous structure and directly bonded with Al2O3powders. Using the Ni-P-coated Al2O3powders, a dense Al2O3-Ni-P composite can be successfully obtained using the hot press process at 1,350°C for 1 hour in an Ar atmosphere under an applied pressure of 30 MPa. The hot-pressed Al2O3-15 wt.% Ni-P composite showed excellent material properties. Its relative density, Vickers hardness, and fracture toughness were comparatively high: about 99.1%, 2,360 Hv, and 6 MPa·m1/2, respectively. The fracture surface of the hot-pressed Al2O3-Ni-P composite showed a semiductile mode due to the mixed intergranular and transgranular fracture mode. In particular, the fracture toughness of the hot-pressed Al2O3-15 wt.% Ni-P composite was strongly enhanced by the combined action of the crack branching and the crack deflection.
Highlights
Aluminum oxide has been used in structural components in the last 100 years [1]
From the study on the microstructure of Al2O3-Ni-P composite powders synthesized via electroless deposition and from the characterization of their hot-pressed Al2O3-Ni-P composite, the following results were obtained: (1) In the as-received Al2O3-Ni-P composite powders, Ni-P contents of the Ni-P-coated Al2O3 powders were measured as 10.9, 14.4, and 20.4 wt.%
Al2O3 surface was directly coated with the nanosized Ni-P coating layer with an amorphous structure, and the coating layer was about 5 nm thick
Summary
Aluminum oxide has been used in structural components in the last 100 years [1]. The improvement of its mechanical properties has been considered a toughening mechanism though the microstructures control approach. The microstructural improvement of aluminum oxide, such as its fine particle and grain size, is expected to enhance its fracture strength according to the Hall-Petch equation [5]. A toughening mechanism using a second phase addition of metallic materials such as Ni, Co, Mo, and Ag can efficiently reduce the crack propagation because the dispersion of the ductile metals caused the plastic deformation [6, 7]
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