A study of the effects of phosphorus on the kinetics of recrystallization and mechanical properties of Ni₂Cr alloy

Abstract

The recrystallization process of 50% cold-rolled Ni₂Cr alloy, with phosphorus (P) contents of 0.002, 0.0017 and 0.078 wt% was investigated, in specimens annealed at temperatures from 600 to 100° C, for times ranging from 10 to 60 min, as functions of surface hardness and microstructure change. It was found that annealing at temperatures below 700° C for times less than 30 min resulted in an increase in hardness from about 430 to 50 KH, depending on the phosphorus content. This increase was thought to be due to interactions between dislocations and the strain fields of impurity atoms such as phosphorus. It was also found that phosphorus increases the activation energy of the recovery and recrystallization process, from about 23 to 27 kcal mol⁻¹ for low and medium phosphorus material to 43 kcal mol⁻¹ for high phosphorus material. The effects of thermomechanical treatment and order transformation on the mechanical properties of Ni₂Cr alloy with 0.002 and 0.078 wt% P were also studied. It was found that 50% cold-working increases the yield stress of 0.002 and 0.078 wt% P materials by 190% and 145%, respectively, compared to the solution-annealed materials. Similarly, an increase in yield stress of 106% and 85%, respectively, was observed for 0.002 and 0.078 wt% material, which was transformed to the long-range ordered condition.