Abstract Structural transitions of metastable Ti1xAlxN coatings on technically relevant substrates were determined as a function of the Ti/Al ratio. Ti1xAlxN films with different Ti/Al ratios were deposited on high speed steel (HSS) substrates at substrate temperatures of 300 and 500C by means of reactive magnetron sputtering ion plating (MSIP). A Ti/Al compound target was used as well as a cluster arrangement of one Ti and one Al target for comparison. The composition of the films was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). The analyses revealed that films deposited with Ti/Al ratios of 44/56 and 36/64 had grown in cubic NaCl structure, a film with a Ti/Al ratio of 32/68 was two-phase, and a Ti/Al ratio of 25/75 led to a hexagonal film in wurtzite structure. Only small differences of the lattice parameters could be observed in dependence of temperature: At 300C the lattice parameters of the cubic structure corresponded exactly to Vegards law, whereas they slightly decreased in the films deposited at 500C. The application of a cluster arrangement instead of a compound target resulted in nearly the same lattice parameters and peak shapes.