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.

Additive manufacturing processes allow the production of geometrically complex lightweight structures with specific material properties. However, by contrast with ingot metallurgy methods, the manufacture of components using this process also brings about some challenges. In the field of microstructural characterization, where mostly very fine structures are analyzed, it is thus indispensable to optimize the classic sample preparation process and to furthermore implement additional preparation steps. This work focuses on the metallography of additively manufactured Ti‑6Al‑4V components produced in a selective laser melting process. It offers a guideline for the metallographic preparation along the process chain of additive manufacturing from the metal powder characterization to the macro- and microstructural analysis of the laser melted sample. Apart from developing preparation parameters, selected etching methods were examined with regard to their practicality.

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During the last decades, titanium alloys have been of great interest for lightweight applications due to their high strength in combination with a low material density. Current research activities focus on the investigation of near‑α titanium alloys produced by laser powder bed fusion (LPBF). These alloys are known for their superior tensile strength and high creep resistance. This study focuses on the optimization of post‑process heat treatments and the impact on tensile and creep strength of a LPBF produced Ti6242S alloy. Therefore, a variety of annealing steps were conducted to gain knowledge about the decomposition process of the non-equilibrium as-built microstructure and the arising influence on the mechanical properties. Components made of Ti6242S and produced by LPBF reveal an extraordinarily high ultimate tensile strength of about 1530 MPa at room temperature, but show a low elongation at fracture (A5 = 4.3 %). Based on microstructure-property relationships, this study recommends precise heat treatments on how to improve the desired mechanical properties in terms of strength, ductility as well as creep resistance. Moreover, this study shows a triplex heat treatment, which enhances the elongation at fracture (A5) to 16.5 %, while the ultimate tensile strength is still at 1100 MPa.

Creep resistant low-alloyed 2.25Cr-1Mo-0.25V steel is typically applied in hydrogen bearing heavy wall pressure vessels in the chemical and petrochemical industry. For this purpose, the steel is often joined via submerged-arc welding. In order to increase the reactors efficiency via higher operating temperatures and pressures, the industry demands for improved strength and toughness of the steel plates and weldments at elevated temperatures. This study investigates the influence of the post weld heat treatment (PWHT) on the microstructure and mechanical properties of 2.25Cr-1Mo-0.25V multi-layer weld metal aiming to describe the underlying microstructure-property relationships. Apart from tensile, Charpy impact and stress rupture testing, micro-hardness mappings were performed and changes in the dislocation structure as well as alterations of the MX carbonitrides were analysed by means of high resolution methods. A longer PWHT-time was found to decrease the stress rupture time of the weld metal and increase the impact energy at the same time. In addition, a longer duration of PWHT causes a reduction of strength and an increase of the weld metals ductility. Though the overall hardness of the weld metal is decreased with longer duration of PWHT, PWHT-times of more than 12 h lead to an enhanced temper resistance of the heat-affected zones (HAZs) in-between the weld beads of the multi-layer weld metal. This is linked to several influencing factors such as reaustenitization and stress relief in the course of multi-layer welding, a higher fraction of larger carbides and a smaller grain size in the HAZs within the multi-layer weld metal.