As a strong β-stabilizing alloying element, Mo has gained importance for intermetallic β/γ-TiAl alloys. In general, TiAl alloys containing a significant volume fraction of the disordered body-centered cubic β-phase exhibit improved processing characteristics during hot-working. To increase the understanding of the alloying effect of Mo, a model alloy with the chemical composition Ti-44Al-7Mo-0.1B (in at.%) was investigated. In this work, the microstructural evolution after individual heat-treatment steps was studied by means of scanning as well as conventional and in-situ transmission electron microscopy. Additionally, macro-hardness and nanoindentation measurements were conducted to study the change in hardness due to grain refinement and solid-solution hardening. The variation of the observed macro- and nano-hardness corresponds well with the microstructural evolution. The obtained grain refinement effect leads to a significant increase in the macro-hardness, whereas the increase in the average nano-hardness of the individual phases is related to solid-solution hardening.

This study aims to investigate additively manufactured Ti6242S specimens compared with the widely used Ti64 alloy with a special focus on microstructure and mechanical properties as well as the impact of subsequent heat treatments. As the Ti6242S alloy, which belongs to the family of near‐α Ti‐alloys, is often used at higher service temperatures, uniaxial tensile tests are performed at a room temperature up to 500 °C. By means of optical and electron microscopy, it is found that the as‐built microstructure consists of acicular α′ martensite, which decomposes to α + β during the subsequent heat treatment. A special focus on the prior microstructure shows that the Ti6242S alloy has a small β grain size, which influences the resulting α′ microstructure after the β → α′ phase transformation. Furthermore, the mechanical properties at room temperature as well as elevated temperatures exceed the values for selective laser melted Ti64 and conventionally cast Ti6242 material. The heat‐treated Ti6242S specimens exhibit an ultimate tensile strength of about 1213 MPa including a ductility of 11.3% at room temperature. These values may path the way to a substitution of the widely used Ti64 alloy by the near‐α Ti6242S alloy, especially for highly loaded components at elevated temperatures.

In the literature, the effects of nitrogen on the strength of austenitic stainless steels as well as on cold deformation are well documented. However, the effect of N on fatigue behaviour is still an open issue, especially when comparing the two alloying concepts for austenitic stainless steels-CrNi and CrMnN-where the microstructures show a different evolution during cyclic deformation. In the present investigation, a representative sample of each alloying concept has been tested in a resonant testing machine at ambient temperature and under stress control single step tests with a stress ratio of 0.05. The following comparative analysis of the microstructures showed a preferred formation of cellular dislocation substructures in the case of the CrNi alloy and distinct planar dislocation glide in the CrMnN steel, also called high nitrogen steel (HNS). The discussion of these findings deals with potential explanations for the dislocation glide mechanism, the role of N on this phenomenon, and the consequences on fatigue behaviour.

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