Aging-Induced η Phase Precipitation and Hardness Evolution in C286 Alloy
摘要
The C286 alloy enhances its mechanical properties through the precipitation of the γ′-Ni3(Ti,Al) phase during aging; however, the η-Ni3Ti phase forms during conventional heat treatment. To investigate the precipitation behavior of the η phase and its impact on hardness, this study examines C286 alloy subjected to hot-working deformations of 19.70, 48.96, and 78.07%, following solid solution treatment at 1000 °C for 1 hour and aging at 400-900 °C for 2.5 and 16 hours, respectively. The results demonstrate that the η phase reduces hardness, with larger sizes and higher densities leading to lower hardness values. For the 2.5-hour aging treatment, the hardness peaked at HV332–339 at 780 °C, declining thereafter due to η phase precipitation (780-900 °C). For the 16-hour aging treatment, the hardness reached a maximum of HV342–350 at 750 °C, decreasing with extensive η phase precipitation (750-900 °C). During aging at 870 °C for 16 hours, the hardness slightly increased due to a reduction in η phase density and an increase in γ′ phase density. Prolonged aging lowered the precipitation temperature of the η phase and increased its quantity at the same temperature. The hardness is governed by the interplay between the γ′ and η phases.