A combination of parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE) asa novel combined severe plastic deformation (SPD) was applied on AZ91 alloy to produce ultrafine-grained (UFG) thinwalledtubes. The effects of combined SPD process were investigated on the microstructure refinement and mechanicalproperties. Also, hydro-bulge test was carried out to reveal the mechanical properties. The results showed a notable increasein ultimate strength, yield strength and microhardness of the thin-walled UFG tube were achieved compared to that fromPTCAP process. A remarkable grain refinement achieved. Applying three-passes-combined process refine the grain sizeto 8.8 $\mu$m from an initial value of $\sim$150 $\mu$m. For one pass- and two passes-processed thin-walled tubes, it was about 12.4 and 9.8 $\mu$m, respectively. Yield and ultimate strengths were increased notably to 150 and 354 MPa for 2P $+$ TBE tube, from the initial values of 86 and 166 MPa, respectively. The maximum microhardness was increased to about 105 Hv for the2P S+$ TBE tube from the initial value of 56 Hv. Hydro-bulge test showed that the bursting pressure increased to 246 bar for2 passes-thin-walled tube from the initial value of 160 bar. It was 220 and 195 bar for 1 pass- and 3 passes-thin-walled tubes,respectively.
Volume 43, 2020
Continuous Article Publishing mode
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