The Age-Hardening Mechanism of Nanocrystalline Ni-P Alloys Synthesized by Electrodeposition

Abstract

Strengthening mechanism of age-hardenable electrodeposited Ni-P alloy was investigated focusing on the role of Ni3P precipitates in nanocrystalline structures. Specimens were synthesized by electrodeposition followed by aging treatment at temperatures raging from 473 to 773 K. As-electrodeposited structures became only Ni phase and Ni3P precipitated by the subsequent aging treatment. Distribution of grain size of Ni matrix was examined in detail by field-emission type transmission electron microscopy. The specimens became harder with higher P content after the electrodeposion and aging treatment. After the aging treatment 573 K or bellow, average grain size of Ni matrix was under 10 nm. On the other hand, after aging at 673 and 773 K both the grain size of Ni matrix and Ni3P particle size grow to be comparable. It is considered the hard interphase boundary to the dislocation slip is responsible to the hardening rather than the classical precipitation hardening.