An in-situ time resolved 2D diffraction and microscopy measurements were conducted at elevated temperature to study the directional atomic rearrangements during transformations between the α- and γ-phases in titanium aluminides. Phase transition from α2-Ti3Al to γ-TiAl, which had been followed in both reciprocal and real space, was found to appear homogeneously over the bulk and occur through an oriented rearrangement of atoms. Metallurgical investigations, including microscopy and conventional diffraction based structure and phase analysis, were performed off-situ on quenched and subsequently prepared samples. The phase evolution of the composition Ti-45Al-7.5Nb (concentration in atomic %) was also investigated. It was also concluded that similar transformations take place in several other material systems relevant for fundamental and applied research.