R.K. Sabat

Effect of pre-annealing strains on annealing texture developments in commercially pure (CP) titanium

Hexagonal commercially pure titanium (cp-titanium) plates were subjected to unidirectional-rolling (rolling), accumulative roll-bonding (ARB) and cross-rolling in a laboratory rolling mill. Rolling and cross-rolling were carried out to impart 90% reduction in thickness and ARB processing was performed for six passes. The deformed plates were then subjected to annealing at 600 °C for a large range of soaking time starting from 0.17 min (10 s) to 30 min. It was observed that the samples were fully recrystallized after 5 min of annealing, irrespective of the rolling processes employed in this study. Also, the samples were seen to develop almost similar texture when annealing was carried out beyond 5 min of annealing time. However, before annealing, the texture development was seen to be different in the respective samples subjected to different rolling processes. The initial texture present in the deformed structure got strengthened during annealing of the samples under investigation. It was also observed that the texture development was insignificant in ARB-processed samples after annealing.

Improvement in mechanical properties of commercially pure titanium through reverse rolling

Abstract Commercially pure (cp) titanium plates were subjected to 90% reduction in thickness through UDR (unidirectional rolling) and RR (reverse rolling) in the cold-rolling route. These rolled plates were then annealed at 600 °C for 20 min. The plates processed through UDR and RR exhibited similar values of ductility, but the plates subjected to RR exhibiting a significant increase in their strength compared to those rolled through UDR. However, on annealing the yield strength of the RR plate was reduced slightly while its ductility improved. Relative growths of dislocation density in the samples appeared to be responsible for such differences in the mechanical properties of the samples.

Mechanism of texture and microstructure evolution during warm rolling of Ti–6Al–4V alloy

ABSTRACT Ti–6Al–4V (Ti64) plates were subjected to rolling at 600°C and 800°C, respectively, for reductions up to 90% reduction in thickness. The mechanism of texture and microstructure evolution during rolling was studied in the present study. Extension twins of coherent nature were observed in the samples rolled up to 50% of reduction. The deformation was relatively inhomogeneous in the samples rolled at 600°C compared to that at 800°C. Visco-plastic self-consistent (VPSC) simulation showed that relative activity of pyramidal slip was higher during rolling at 800°C compared to that at 600°C. The average activity of slip systems per grain was less than five for the samples rolled at 600°C and this might be responsible for the strain heterogeneity in the large grains. Further, twinning activity was found to be limited to a true strain of 0.5, as supported by the microstructural observation. VPSC simulation also showed the presence of contraction twins in the samples which was further supported by X-ray texture measurement. Dominant basal texture was observed in the samples irrespective of the temperature of rolling.