L1 ordering and δ' precipitation in Al-Cu-Li.

The precipitation mechanism of the δ' (AlLi) phase in Al-Li alloys has been controversially discussed in recent decades, specifically with respect to a conjectured congruent ordering process. However, kinetics in the Al-Li system does not allow to resolve the intermediate stages of precipitation and hence to experimentally clarify this issue. In this paper, we are revisiting the subject in ternary Al-Cu-Li alloys with pronouncedly slower kinetics, employing Transmission Electron Microscopy, High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy, Differential Scanning Calorimetry and Atom Probe Tomography.

Time evolution of morphology in mechanically alloyed Fe-Cu.

Being widely accessible as well as already utilised in many applications, Fe-Cu acts as an ideal binary model alloy to elaborate the enforced nonequilibrium enhanced solubility in such a solution system that shows a limited regime of miscibility and characterised by a large positive heat of mixing. In addition to the detailed analysis of ball milled Fe-Cu powders by means of Atom Probe Tomography (APT), site specific structural analysis has been performed in this study using Transmission Electron Microscopy (TEM). In this contribution results on powders with low Cu concentrations (2.

Evaporation mechanisms of MgO in laser assisted atom probe tomography.

In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO.

Transmission electron microscopy and atom probe specimen preparation from mechanically alloyed powder using the focused ion-beam lift-out technique.

The preparation of transmission electron microscopy (TEM) and atom probe-field ion microscopy (AP-FIM) specimens from mechanically alloyed Ti-Cu-Ni-Sn powder has been explored. Applying the focused ion beam (FIB) based in situ lift-out technique, it has been demonstrated that specimen preparation can be carried on single micrometre-sized powder particles without the use of any embedding media. Since the particles did not incorporate any micropores, as revealed by cross-sectioning, the standard procedure known for bulk samples could be simply implemented to the powder material.

Application of focused ion beam to atom probe tomography specimen preparation from mechanically alloyed powders.

Focused ion-beam milling has been applied to prepare needle-shaped atom probe tomography specimens from mechanically alloyed powders without the use of embedding media. The lift-out technique known from transmission electron microscopy specimen preparation was modified to cut micron-sized square cross-sectional blanks out of single powder particles. A sequence of rectangular cuts and annular milling showed the highest efficiency for sharpening the blanks to tips.