Effect of Friction Stir Processing Procedures on Microstructure and Mechanical Properties of Mg-Al-Zn Casting

Abstract

Cast Mg-Al-Zn (AZ80) alloy was subjected to friction stir processing (FSP) with three different FSP procedures: single pass, single pass with a pre-solution treatment (pre-ST), and two pass. FSP resulted in remarkable grain refinement, significant breakup, and dissolution of the coarse, networklike Mg 17 Al 12 phase. While the single-pass FSP procedure produced a heterogeneous microstructure with Mg 17 Al 12 particle-rich bands, both the pre-ST FSP and the two-pass FSP procedures resulted in the generation of a uniform microstructure. The pre-ST FSP and twopass FSP samples exhibited significantly enhanced strength and ductility due to remarkable grain refinement and dissolution of coarse Mg 17 Al 12 phase. A post-FSP aging resulted in the precipitation of fine Mg 17 Al 12 particle, thereby increasing the strength of the FSP samples. Among three FSP samples, the aged two-pass FSP sample exhibited the highest ultimate tensile strength (UTS) of 356 MPa and an elongation of 17 pct.

Microstructure evolution and mechanical properties of a submerged friction-stir-processed AZ91 magnesium alloy

“…Presently, research on FSP of magnesium alloy has been widely reported (summarized in Table 1) [7][8][9][10][11][12][13][14][15]. According to the different processing parameters, the average grain size of a-Mg varies in the range of 2.5-15 lm.…”

Enhanced mechanical properties of Mg–Gd–Y–Zr casting via friction stir processing

“…Investigations of AZ91D and AZ80 castings indicated that FSP resulted in significant breakup and dissolution of the coarse, network-like eutectic ␤-Mg 17 Al 12 phase distributed at the grain boundaries and remarkable grain refinement, producing a fine-grained supersaturated solid solution. A post-FSP aging then resulted in the precipitation of the fine ␤-Mg 17 Al 12 particles, enhancing the mechanical properties of the AZ91 and AZ80 castings significantly [21][22][23]. Considering the fact that the Mg-Gd-Y alloys, such as Mg-10Gd-3Y-0.5Zr (GW103), contain a great number of thermally stable Mg 5 (Gd,Y) particles, it would be very interesting to know whether FSP could achieve the dissolution of the coarse heat-resistant intermetallic particles in the Mg-Gd-Y casting as in the Mg-Al-Zn castings [21][22][23].…”

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

“…Similarly, it was reported that the two-pass FSP with a 100 pct overlap produced more homogeneous microstructure in AZ80 magnesium alloy casting than singlepass FSP. [37] The microstructure in the center of the second FSP was similar to that in the single-pass FSP (Figure 6(c)). The TZ between the two passes showed different macrostructures from the top to the bottom For the three-pass overlapping FSP (Figure 2(c)), the torchlike flow patterns in the remnant regions of the first and second FSPs were obvious (Figures 7(a) and (b)), but the latter was greatly weakened and this was due to the effect of multiple-pass FSP.…”