High strength microduplex Cu-Ni-Zn alloys

Abstract

High ambient temperature tensile and fatigue strengths have been obtained in two-phase α-β Cu-Ni-Zn alloys (nickel silvers) by controlled thermomechanical working. The thermomechanical working operation involves cold working of solution annealed stock, followed by annealing in the two-phase region. This results in simultaneous recrystallization and precipitation yielding a fine-grained two phase microstructure termed “microduplex”. The high mechanical properties obtained are attributed to the fine-grained two-phase microduplex microstructure. Compositional variations studied included 10 to 40 pct Ni, 35 to 40 pct Zn, balance Cu. On the basis of ease of processing and mechanical properties, a particularly attractive composition is Cu-15Ni-37.5Zn, designated IN-836. Typical room temperature properties of IN-836 in the microduplex condition include 100 ksi (690 MN/m²) yield strength with 25 pct elongation and 40 ksi (275 MN/m²) fatigue limit (10⁷ cycles). Finally, superplastic behavior has been observed in IN-836.