Mechanical property and microstructure evolution of nitrogen-modified Ti-6Al-4V alloy with core-shell structure by hot compression

Core-shell (CS) structured Ti-6Al-4V (Ti64) alloy with single a shells and duplex alpha + beta cores was fabricated by powder nitriding and spark plasma sintering. The mechanical property and microstructure evolution of CS-Ti64 alloy was investigated by compression at temperatures of 950-1100 degrees C and strain rates of 0.001(-1) s(-1). The nitrogen-induced solid solution strengthening and the nitrogen-stabilized CS structure significantly enhanced the compressive strength. Microstructure evolution of CS-Ti64, involved inhomogeneous deformation of the core and shell, which was quite different from that of the commercial Ti64. Regions adjacent to shells and central locations of cores suffered large strain and therefore preferentially underwent dynamic recrystallization (DRX). The deformation mechanism of the novel CS-Ti64 alloy was discussed in terms of the a shells, a laths and DRX.