Data on a Laves phase intermetallic matrix composite in situ toughened by ductile precipitates

The data presented in this article are related to the research article entitled “Laves phase intermetallic matrix composite in situ toughened by ductile precipitates” (Knowles et al.) [1]. The composite comprised a Fe2(Mo, Ti) matrix with bcc (Mo, Ti) precipitated laths produced in situ by an aging heat treatment, which was shown to confer a toughening effect (Knowles et al.) [1]. Here, details are given on a focused ion beam (FIB) slice and view experiment performed on the composite so as to determine that the 3D morphology of the bcc (Mo, Ti) precipitates were laths rather than needles. Scanning transmission electron microscopy (S(TEM)) micrographs of the microstructure as well as energy dispersive X-ray spectroscopy (EDX) maps are presented that identify the elemental partitioning between the C14 Laves matrix and the bcc laths, with Mo rejected from the matrix into laths. A TEM selected area diffraction pattern (SADP) and key is provided that was used to validate the orientation relation between the matrix and laths identified in (Knowles et al.) [1] along with details of the transformation matrix determined.


a b s t r a c t
The data presented in this article are related to the research article entitled "Laves phase intermetallic matrix composite in situ toughened by ductile precipitates" (Knowles et al.) [1]. The composite comprised a Fe 2 (Mo, Ti) matrix with bcc (Mo, Ti) precipitated laths produced in situ by an aging heat treatment, which was shown to confer a toughening effect (Knowles et al.) [1]. Here, details are given on a focused ion beam (FIB) slice and view experiment performed on the composite so as to determine that the 3D morphology of the bcc (Mo, Ti) precipitates were laths rather than needles. Scanning transmission electron microscopy (S (TEM)) micrographs of the microstructure as well as energy dispersive X-ray spectroscopy (EDX) maps are presented that identify the elemental partitioning between the C14 Laves matrix and the bcc laths, with Mo rejected from the matrix into laths. A TEM selected area diffraction pattern (SADP) and key is provided that was used to validate the orientation relation between the matrix and laths identified in (Knowles et al.) [1]

Data
Here we report data obtained from a Fe-30Ti-10Mo (at%) alloy [1]. This alloy was selected to explore the toughening effect of A2 (Mo, Ti) precipitates produced within a Laves phase intermetallic matrix composite during heat treatment. Here, we present the microstructure in 3D from a focused ion beam (FIB) slice and view experiment, as well as scanning transmission electron microscopy (S(TEM)) micrographs, energy dispersive X-ray spectroscopy (EDX) maps, a TEM selected area diffraction pattern (SADP) and details of the transformation matrix determination provided in [1].

Experimental design, materials and methods
Full details of the preparation of the alloy are provided in [1]. The Fe-30Ti-10Mo (at%) alloy was produced by arc melting 499.9 at% purity elements under an argon atmosphere. Sections of the ingot were encapsulated within quartz ampoules under argon and aged at 1000°C for 500 h, followed by water quenching.
An FEI Helios NanoLab 600 dual beam FIB-scanning electron microscopy (SEM) system was used to perform a slice and view experiment through a~15×15×15 µm volume by sequential FIB slicing followed by collection of secondary electron (SE) micrographs. The SE micrographs were then binarised and segmented using ImageJ to separate the C14 and A2 (bcc) phases, after which the images were stacked and an iso-surface produced using the Avizo software package.
Electron transparent foils for transmission electron microscopy (TEM) were produced by electropolishing using a solution of 10 vol% perchloric acid in methanol at −30°C and 18 V, followed by final polishing using a GATAN precision ion polishing system operated at 5 kV, as in [1]. TEM and scanning TEM (STEM) were carried out using JEOL 2100F and FEI Osiris microscopes respectively.
From SEM micrographs of the aged alloy characterised in [1] uncertainty existed as to whether the precipitated A2 phase occurred as laths or as needles. In order to resolve this, a FIB slice and view experiment was performed, an example binarised SEM SE micrograph from which is shown in Fig. 1b. The 3D surface reconstruction of the laths in the Fe60Ti30Mo10 heat treated alloy can be seen in Fig. 1 along with x-y, x-z and y-z slices of the reconstruction. From this, it was identified that the A2 phase does occur as laths and not as needles [1].
In order to study the chemical segregation between the fine scale A2 plates and the C14 matrix STEM-EDX was employed, Fig. 2. The high-angle annular dark-field (HAADF)-STEM micrograph in Fig. 2a showed phase contrast similar to that observed in SEM imaging [1], with the C14 matrix 5 µm 10 µm  appearing dark and the A2 plates bright according to their relative average Z. STEM-EDX maps for Fe, Ti and Mo, Fig. 2b-d Fig. 3 that was used to validate the orientation relation and transformation matrix between the matrix and laths identified in [1]. Further details of the determination of the transformation matrix are included in the Appendix.