Local variations of the chemistry in as‐cast γ‐TiAl (TiB_x) alloys and its consequence for thermomechanical treatments

Abstract

The first part of the paper presents an accompanying investigation to a thermomechanical processing route of gamma-TiAl turbine blades. By means of scanning electron microscopy and energy dispersive X-ray (EDX) analysis, the chemical homogeneity and the microstructures of gamma-TiAl as-cast ingots, work pieces and the final turbine blades are determined. We find that the local Al-content in as-cast ingots can vary by more than 1.5 at.%. Large chemical inhomogeneities present in as-cast ingots can only be eliminated to a certain degree by subsequent thermomechanical processing. An additional aim of the study is to assess the influence of a thermomechanical processing on the morphology of titanium boride precipitates and the alpha2-Ti3Al-phase. The second part of the paper contains a detailed analytical study devoted to homogenization of a range of gamma-TiAl cast alloys. Different microstructures are generated in a laboratory-scale argon-arc furnace by both rapid and slow solidification rates and an additional homogenization treatment, respectively. Quantitative EDX analysis shows that only rapid solidification of ingots with a subsequent homogenization treatment leads to a nearly chemically homogeneous microstructure.

The effect of 12‐O‐tetradecanoylphorbol‐13‐acetate on Sertoli cell morphology and cytoskeletal organization: an in vitro study by means of cryo‐SEM and fluorescent techniques

“…Thus, the in vitro changes of cytoskeletal organization on immature Sertoli cells after the application of TPA could reflect analogous alterations in the physiological morphogenesis and function of the seminiferous tubules of the adult testes. During the past decade, SEM has been increasingly used in material sciences (Chedru et al, 1999;Denry et al, 1999;Severini et al, 1999;Sternitzke et al, 1999) as well as in biomedical applications (Mironov and Mironov, 1985;Mitsushima and Katsumoto 1990;Gallego et al, 1997;Wang et al, 1997;Okanue et al, 1998;Wang et al, 1998;O'Donell et al, 1999;Sakamoto et al, 1999). In the present work the cells were observed at a frozen hydrated state in a SEM equipped with a cold stage at -185°C.…”

An Advanced TiAl Alloy for High-Performance Racing Applications

“…The starting ingot diameter must be increased to achieve the desired degree of deformation while keeping the final dimension almost constant. Hence, the occurrence of segregations, as well as an unsuitable microstructure, is assumed to become more likely within this condition [ 51 ]. This may be the reason for the lower average tensile values of the φ = 1.9 compared to the φ = 1.4 specimens.…”