Effect of Multiple-Pass Friction Stir Processing Overlapping on Microstructure and Mechanical Properties of As-Cast NiAl Bronze

Abstract

As-cast Cu-9Al-4.5Ni-4Fe NiAl bronze alloy (NAB) was subjected to multiple-pass friction stir processing (FSP) with a 50 pct overlap. After FSP, the coarse microstructure of the base metal (BM) was transformed to defect-free material with fine microstructure. While the torchlike patterns in the stir zone (SZ) and the uplifted grains in the transitional zones (TZs) between two passes were observed in the multiple-pass FSP region, no grain coarsening was found in the remnant zone of the previous SZ after subsequent FSP pass. The hardness value of the FSP materials was higher than that of the BM and was homogeneously distributed throughout the entire multiple-pass FSP region. The FSP materials showed greatly improved tensile properties compared to the BM, and the TZs showed similar tensile strength and ductility to the single-pass FSP materials. The BM broke in a mixture mode of brittle cleavage and microvoid coalescence fracture, whereas the FSP and TZ samples failed in the latter fracture mode. The results showed that the multiple-pass overlapping (MPO) FSP was feasible to modify the microstructure of large-sized plate of the NAB.

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

“…In region B and C, the microstructure also contains α, fine κII, and β′ phases, while the α phase has different morphologies between regions B and C. The morphology of α phase in region B is banded and that in region C is stream-like. According to Ni's study [19,20], the banded and stream-like α structure results from the incomplete dynamic recrystallization and intense plastic deformation during friction stir processing. Figure 3b, α grains boundaries and fine voids are clearly observed.…”

Investigation of microstructure and mechanical properties of hot worked NiAl bronze alloy with different deformation degree

“…Several plastic deformation techniques had been used to improve the mechanical properties of cast NAB alloys such as equal channel angular extrusion (ECAE) [7,8], friction surfacing (FS) [9] and friction stir processing (FSP) [10][11][12] etc. It is well reported that the plastic deformation significantly improves the mechanical properties of as-cast NAB alloy [13,14]. Ni et al [12,13] found that inhomogeneous microstructures were formed during FSP due to different deformation degree through stir zone.…”

“…It is well reported that the plastic deformation significantly improves the mechanical properties of as-cast NAB alloy [13,14]. Ni et al [12,13] found that inhomogeneous microstructures were formed during FSP due to different deformation degree through stir zone. Gao et al [7,8] reported that the grain of the alloy was decreased with the increase of the pass number of ECAE and the mechanical properties were significantly improved after ECAE.…”

Effect of Multiple-Pass Friction Stir Processing on Hardness and Corrosion Resistance of Martensitic Stainless Steel

“…The translation of the rotating tool creates a characteristic asymmetry between the two sides of the processed zone, one is the advancing side (AS), where the direction of the tool rotation is the same as that of the tool translation, and the other one is the retreating side (RS), where the direction of the tool rotation is opposite to that of the tool translation [4]. FSP is applied for various purposes including fabricating surface composites [5], microstructural homogeneity [6,7], surface modification or hardening [8], and grain refinement [9].…”