Figure 1.(a) In-situ TEM images at RT; (b) In-situ XRD data from RT to 350°C after 22 minutes. In-situ TEM images at various temperatures between 200 and 350°C:  (c) when sample reached 200°C; (d) after 5 minutes at 200°C, with the diffraction pattern for AlCu (η-phase) with [020] orientation; (e) after 10 minutes at 300°C; (f) when sample reached 350°C; (g) after 1 minute at 350°C, with the diffraction pattern for Al2Cu (θ-phase) with [200] orientation; (h) after 22 minutes at 350°C. (Note: ‘A’ represents the Al-Cu interaction area (solid solution (Al,Cu). ‘B’ shows the voids at the Al-Cu interface that indicate the Cu had diffused to the Al layer. ‘C’ indicates the AlCu composition (η-phase). ‘D’ represents the Al2Cu phase. ‘E’ shows the Cu path to Al-Cu.