In Situ Synchrotron X-ray Study of the Mechanical Properties of Pure Mg Produced by Powder Metallurg
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In this study, two pure magnesium materials made via powder metallurgy were subjected to in situ synchrotron X-ray studies with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors. Each of the two materials has a porosity of less than 0.5%, according to SAXS analysis. In order to examine the dislocation evolution during material deformation, line broadening analysis was done on the diffraction patterns gathered by WAXS. Tensile deformation is dominated by -type dislocation in both activity materials. It is also explored how grain size and texture affect the different tensile behavior of these two materials.
Figure 1. Powder metallurgy (PM) process flow and sample position of tensile samples (Li et al., 2020).
Using spherical particles ranging from 2.2 to 10 µm and a lognormal distribution (measured by Brunauer-Emmet-Teller (BET)), gas-atomized pure Mg powders (99.7% by weight) from a direct current arc plasma evaporation device were cold pressed by a 2000 KN hydraulic press machine. The consolidated powders were either milled out (DH) or heat-treated for one hour at 500 ° C before being milled out (FPS). Can-sheathed powders were compacted at 200 ° C, stripped, and used as extrusion feedstock. The feedstock was maintained at 350 ° C for 0.5 hours before being extruded at a temperature of 300 ° C, a ratio of 25:1, and a speed of 11 mm/s. Figure 1 depicts the two materials' processing processes.
Figure 2. In situ tensile experimental setup at beamline 1-ID of the advanced photon source (APS) concurrent with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors. The arrow on the GE3 detector indicates the azimuthal direction of focus in this work (Li et al., 2020).
Electrical discharge machining was used to create flat dog-bone tensile specimens with gauge dimensions of 5.0 mm (L) x 1.2 mm (W) x 1.0 mm (T) from the extruded bar (EDM). Perpendicular. Using the Advanced Photon Source's 1 -ID beamline, the uniaxial tensile experiment was carried out at a strain rate of 2 x 10 -4 s -1 . Figure 2 shows the simultaneous collection of WAXS and SAXS signals during specimen loading.
Figure 3. Estimation of the porosity in the milled-out specimen (DH) using SAXS line profile (Li et al., 2020).
Nano-measurement software was used to measure the grain size using the linear intercept method. The grain size was determined for both DH and FPS using a minimum of three photos. For DH material and FPS material, respectively, the average grain size is 3.1 µm and 11.6 µm. As compared to the original powders, which have a lognormal grain size distribution, the DH sample's grain size is very similar. Both the Archimedes test and the SAXS measurement indicated that the porosity in these two materials was less than 0.5%. (see Figure 3).
References
[1] Li, L., Wang, L., Wang, J., Zhang, H., Zhu, Q., Li, Z., & Zeng, X. (2020). In situ synchrotron x-ray study of the mechanical properties of pure mg produced by powder metallurgy. Metals , 10 (9), 1–11. https://doi.org/10.3390/met10091198