Effect of Post Heat Treatment on the Microstructure and Microhardness of Friction Stir Processed NiAl Bronze (NAB) Alloy

Yuting Lv,Liqiang Wang,Xiaoyan Xu,Weijie Lu

doi:10.3390/met5031695

Abstract

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.

Highlights

Nickel-aluminum bronze (NAB) alloy is one kind of copper-aluminum alloys
Tang et al [8] reported that laser surface melting improved the corrosion resistance and erosion resistance of cast manganese-nickel-aluminum bronze due to the formation of a homogeneous and single phase microstructure
As-cast NAB alloy is produced by friction stir processing (FSP) and post heat treated at 675 °C for 2 or 4 h, and the effect of post heat treatment on the microstructure and microhardness of FSP NAB alloy is studied

Summary

Introduction

Nickel-aluminum bronze (NAB) alloy is one kind of copper-aluminum alloys. Several techniques have been used to improve both the corrosion resistance and mechanical properties of cast NAB alloy, such as equal channel angular extrusion (ECAE) [5,6], laser surface melting (LSM) [7,8], and friction surfacing (FS) [9]. Tang et al [8] reported that laser surface melting improved the corrosion resistance and erosion resistance of cast manganese-nickel-aluminum bronze due to the formation of a homogeneous and single phase microstructure. Hanke et al [9] found that FS could improve the cavitation erosion of NAB because fine grains and homogeneous microstructure are obtained during friction surfacing

Methods

Results

Conclusion