Effect of Post Heat Treatment on the Microstructure and Microhardness of Friction Stir Processed NiAl Bronze (NAB) Alloy
NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of heat treatment on the microstructure and microhardness is studied. The results show that the microstructure of the FSP NAB alloy consists of high density dislocations, retained β phase (β′ phase) and recrystallized grains. When annealed at 675 °C, discontinuous static recrystallization (DSRX) takes place. The content of β′ phase gradually decreases and fine κ phase is precipitated. After annealing for 2 h, both the microhardness of the FSP sample in the stir zone (SZ) and the difference in hardness between the SZ and base metal decrease due to the reduction of the dislocation density and β′ phase, accompanying recrystallized grain coarsening. With further increasing of the annealing time to 4 h, the aforementioned difference in hardness nearly disappears.
The morphology, crystallography, and chemistry of phases in as-cast nickel-aluminum bronze
The morphology, crystallography, and composition of the phases present in as-cast nickel-aluminum bronze of nominal composition copper-10 wt pct aluminum-5 wt pct nickel-5 wt pct iron have been investigated using optical, electron optical, and microprobe analysis techniques. The as-cast microstructure consists of copper-rich α, martensitic β, and κ-phases based on Fe3Al and NiAl. The κz precipitates have a dendritic morphology and are cored; the composition ranges from iron-rich solid solution to Fe3Al. The κII and κiv precipitates have, respectively, a dendritic and an equiaxed/dendritic morphology, and are based on Fe3Al, while κIII is a eutectoidal decomposition product of lamellar or globular morphology based on NiAl. The κI, κII, and κIII precipitates have the Kurdjumov-Sachs orientation relationship with α matrix. Small κIV precipitates exhibit the Nishiyama-Wasserman orientation relationship with the α matrix, while large κiv precipitates have an orientation relationship which lies between Kurdjumov-Sachs and Nishiyama-Wasserman.
Guidelines for the use of copper alloys ·in seawater*
These guidelines update and extend the charts and data summaries presented in an earlier work, "Guidelines for Selection of Marine Materials," in which many of the copper alloys covered in this review were not included.