Increasing toughness by promoting discontinuous precipitation in Cu–Ni–Si alloys

Abstract

The influence of precipitation morphology, including continuous precipitation (CP) and discontinuous precipitation (DP), on the mechanical behaviour of Cu-Ni-Si alloys was studied. The Cu-6Ni-1.5Si (in wt%) alloy was solution heat treated at 980 °C for 2 h and aged at 500 °C for 0.5 and 3 h to produce CP and DP structures. The DP specimen showed an abnormal increase in tensile ductility with increasing strain rate, unlike the CP counterpart. The impact toughness of the DP specimen was 1.6 times greater than that of CP specimen. The fracture mode in DP specimen was mostly dimpled rupture, while the mixed mode of cleavage fracture and dimpled rupture was noted on the CP specimen.

Behaviour of Small Fatigue Cracks in CU-5.5NI-1.28SI Alloy Round-Bar Specimens

“…For Cu-Ni-Si alloys with high solute concentrations, on the other hand, phase transformation studies have been conducted mainly to control the microstructure of the alloy [7], [8]. In addition, discontinuous precipitates (DPs) that were fibre-shaped, stable δ-Ni2Si intermetallic compounds were formed in the Cu matrix [9], [10]. The formation of DPs in Cu-Ni-Si alloys is detrimental to their mechanical properties.…”