Supplementary information
S1. Solubility estimation from HRTEM micrographs:
Size-dependent solubility is confirmed by high-resolution electron microscopy analysis. Fig. S1 shows the high-resolution micrograph revealing the lattice fringes for biphasic particle of size 18 nm. The right segment of the particle having two set of fringes with spacing of 0.261 nm and 0.237 nm can be assigned to (1010) and (0111) lattice fringes of hcp-Cd rich solid solution. The left segment having two sets of fringes spaced 0.274 nm and 0.195 nm can be assigned to (101) and (121) lattice fringes of the Sn-rich phase. We have estimated the lattice parameters ‘a’ and ‘c’ of both the phases of the two-phase inclusion and compared with their pure phases respectively as tabulated in Table. ST1. Assuming Zen’s law is valid in our case, we have estimated the amount of tin dissolved in cadmium and the amount of cadmium dissolved in tin from the lattice parameter data as shown in Fig.S2.
Fig. 2 in the main manuscript shows a single-phase solid solution particle. The
1.201 nm-spaced fringes seen in the particle can be consistently assigned as the
(0112) lattice fringes of the solid solution, while the 0.241 nm ± 0.005 nm spaced fringes can be assigned as the (1011) lattice fringes with the hcp-Cd structure. The lattice parameters ‘a’ and ‘c’ of single-phase inclusion calculated and compared with their pure phases respectively which is tabulated in Table.ST1. The amount of tin dissolved in cadmium and the amount of cadmium dissolved in single-phase particle from the lattice parameter data according to Zens law as shown in Fig. S3.
S2. Summary of phase transformation behavior of different size particles:
The summary of phase transformation behavior of different size range particles has been pictorially presented in Fig. S4. In the as-melt-spun specimens, all the particles having size smaller than 18 nm are single-phase solid solution particles that are shown in yellow color and particles having size greater than 18 nm are two-phase particles (which are shown with red (Cd)-green (Sn) colors). In-situ TEM heating studies show that when the specimen is heated, the single phase solid solution particles first melted at low temperatures within a temperature range of 142˚C to 153˚C that are shown in blue color. After further heating, intermediate size range particles 18-30 nm size particles melted within a temperature range of 160˚C to 185˚C and finally larger particles having size about 100 nm melted within a temperature range of 180˚C to 210˚C. In single-phase particles, the melt nucleated first at particle-matrix interface and in two-phase particles melt nucleated first at triple junction corner and melt grown into Sn-rich phase and later Cd phase melted completely. During cooling, first 100 nm size bigger particles solidified with two-phase structure around 130˚C, later the intermediate size range particles solidified as single-phase particles instead of two-phase particles and hence they are shown with yellow color. Finally, the smallest particles having size less than 18 nm solidified as single-phase particles similar to their initial state. Particle size distribution of phases before and after thermal cycling are shown in Fig. S5.
Table ST1: Comparative composition analysis of 20 particles of different sizes.Sn% / Cd%
Size / Phase / STEM-EDS / HRTEM / STEM-EDS / HRTEM
25 nm
(±5 nm) / Cd segment / 30±5 / 22±7 / 70±4 / 78±7
Sn segment / 80±5 / 70±9 / 20±5 / 30±8
15 nm (±5nm)
(single phase) / Cd segment / 48±7 / 45±10 / 52±7 / 55±10
(b) Sn
Steps
observed Cd
across interface
Al
Figure. S1. (a) and (b) showing high-resolution electron micrographs showing lattice fringes of 18 nm size Sn-Cd embedded particle in Al matrix. FFT from different regions are also shown.
Fig. S2 Plot showing the amount of Sn dissolved in hcp-Cd and the amount of Cd dissolved in Sn for the 18 nm particle (shown in Fig. S1) estimated using Zens law.
Fig. S3 Plot showing the amount of Sn dissolved in single phase, hcp-Cd of 16 nm size (Fig. 2, main paper) estimated using Zens law.
Fig. S4 Summary of phase transformation behavior of different size range of Sn-Cd alloy particles embedded in an Al matrix during melting and solidification.
Figure. S5. Particle size distribution of phases before (a) and after thermal cycling (b).