Strain Mapping of Indented Zr-Based Bulk Metallic Glass Using Nano-Diffraction

The state-of-the-art nano-diffraction technique available at the P06 beamline of the synchrotron radiation source PETRA III was used to observe the strain distribution induced within bulk metallic glass by nano-indentation. Bulk metallic glass (BMG) with nominal composition Zr$_{52.5}$Ti$_{5}$Cu$_{17.9}$Ni$_{14.6}$Al$_{10}$ at.% was prepared by conventional copper mold injection casting. Using the Berkovich indenter a series of indents forming a line was introduced on to the polished surface of the BMG sample. It has been shown that spatially resolved matrix scans with a nanometer sized beam (600 × 600 nm$^{2}$) can identify positions of the indents and quantitatively describe the strain state after nano-indentation

Synchronized Collapse and Formation of Long-Period Stacking and Chemical Orders in Mg85Zn6Y9\mathrm{Mg_{85}Zn_6Y_9}

Long period stacking ordered (LPSO) structures that are synchronized with the chemical order in Mg–TM (transition metal)–RE (rare earth) systems have received special attention as a new type of strengthening phase for Mg alloys. For example, the rapidly solidified powder metallurgy alloy $Mg_{97}Zn_{1}Y_{2}$ with an LPSO phase has a yield strength exceeding 600 MPa [1], while the cast $Mg_{97}Zn_{1}Y_{2}$ alloy with an LPSO phase produced using a hot extrusion process has a yield strength exceeding 350 MPa, which is sufficient for use in many components for airplanes and automobiles [2].The crystalline structures of the LPSO phases in Mg–TM–RE systems have been reported by many researchers [3], [4], [5] and [6], and four types of LPSO phases (10H, 14H, 18R, and 24R) have been reported. The hexagonal ABAB… stacking sequence is changed due to the incorporation of TM and RE concentrate layers. As a result, long period stacking orders are formed along the c axis. Accordingly, rhombohedral (R) and hexagonal (H) Bravais lattices occur, depending on the stacking period of the hcp stacking layer [6].Furthermore, based on scanning transmission and transmission electron microscopy (STEM and TEM, respectively) observations for Mg-Al-Gd alloy, the existence of in-plane ordering has been proposed by Yokobayashi et al. [7]. They found that $L1_{2}-type$ ordered clusters were regularly aligned in the segregated layer. Recently, Egusa et al. revised the crystalline structure models for the 18R- and 14H-type LPSOs of Mg–Zn–Y taking into consideration the in-plane order resulting from the alignment of the $L1_{2}-type$ cluster in the Zn–Y segregated layers [8]. Yamasaki et al. also proposed a 10H-type LPSO crystalline structure in a Mg–Zn–Y alloy [9]. Schematic diagrams of the stacking and in-plane ordering of the 18R-type LPSOs are shown in Fig. 1