Abstract
A Ti–7·5Mn–0·5B alloy has been prepared by consolidation of the rapidly solidified alloy fibres. Examination of the microstructure of the as consolidated alloy, using transmission electron microscopy, shows that the β phase has undergone the initial stage of β→ω transformation, as indicated by the circular diffused streaking in the selected area diffraction patterns from the β phase. At this stage, the bright field image of the β phase shows a mottled contrast, but it is not possible to observe the w phase using either bright or dark field transmission electron micrographs. After aging at room temperature for about six months, the advanced stage of the β→ω transformation has been observed in the β phase. This is evidenced by the discrete spots detected in the ω phase reflections in the selected area diffraction patterns and the centred dark field image taken from the β phase in the aged specimens. The thermodynamic conditions for the β→ω transformation at room temperature and its implications for alloy design have been discussed briefly. During alloy design, the alloy composition should be chosen such that β→ω transformation at room temperature is avoided.
MST/1995
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