Abstract
Omega phase particles can be observed by conventional SEM. Metastable Ti15Mo alloy was annealed at 500 °C for 16 hours. During annealing, ω phase particles grew and got chemically stabilized by expelling Mo atoms. As the result, these ellipsoidal particles, approx. 100 nm long and 50 nm wide can be observed using back-scattered electrons signal in conventional SEM due to chemical contrast. TEM study proved that these particles indeed belong to ω phase. Co-existence of β, ω and α phases was observed. Thin α lamellae were observed along with distorted ω phase particles by TEM.
Highlights
Since the discovery of the ω phase in Ti alloys by Frost et al [1], there have been numerous studies on its formation mechanism and its properties [2]
transmission electron microscopy (TEM) study provided below proves that these small ellipsoidal particles are ω particles. This is the first observation of ω phase particles by standard SEM
The contrast in the backscattered electrons (BSE) image in Figure 1 is given by Z-contrast. ω phase particles are observable due to repulsion of heavier Mo atoms to β matrix
Summary
Since the discovery of the ω phase in Ti alloys by Frost et al [1], there have been numerous studies on its formation mechanism and its properties [2]. Direct observation of ω phase particles is limited to transmission electron microscopy (TEM) due to their small size [7, 8]. Ω phase particles affect subsequent precipitation of α phase during annealing [9, 10].
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