2019 Volume 58 Issue 1 Pages 68-71
Cu-Ni-P alloys are the typical precipitation-hardening material. Thus, Cu-Ni-P alloys are expected to apply alternative materials for heat-exchanger tubes. Therefore, it was investigated that the effect of isothermal artificial aging and the heat-treatment simulated brazing on mechanical properties of Cu-Ni-P alloy in this study. From Vickers hardness test for each artificial aging time, the peak hardness after aging for 10.8 ks achieved at approximately 130 HV. Furthermore, tensile strength of the peak hardness specimen was shown approximately 250 MPa, which was approximately 60 MPa higher than the specimen as solution heat treated. The nominal strain till fracture with isothermal artificial aging was almost equal to the specimen as solution heat treated. These results suggest saving energy in production process for heat exchangers. Spherical or circular precipitates with 5-10 nm diameters were observed in a material which exhibited the peak hardness by transmission electron microscopy. Furthermore, the hardness of specimen as heat-treatment simulated brazing after solution heat treated was shown approximately 105 HV. The peak hardness and tensile strength of the specimen as performed aged at 498 K for 43.2 ks following with the heat-treatment simulated brazing achieved at approximately 140 HV and 260 MPa, respectively. From these results, it is expected the application to higher-strength tube for heat-exchanger after brazing in a furnace.
