Ductility deterioration induced by L21 phase in ferritic alloy through Ti addition

• Ductility deterioration induced by L21-Ni2AlTi precipitates in the aged ferritic alloys was examined systematically by using a combination of scanning transmission electron microscope (STEM), mechanical tests and first-principles thermodynamic calculations. The experimental studies revealed that the strength and hardness of the aged Fe–10Cr–5Ni–1Al–1Ti ferritic alloy containing B2–NiAl and L21-Ni2AlTi precipitates were higher than that of the aged Fe–10Cr–5Ni–1Al ferritic alloy containing NiAl precipitates, whereas the elongation-to-failure decreased dramatically from 9.3% to 0.3% indicating an obvious ductility deterioration due to the formation of L21-Ni2AlTi precipitates. This was also confirmed by the observation of fracture transition mode from dimpled failure to cleavage failure. The first-principles calculations, concerning the precipitate/matrix interface, were carried out to provide a theoretical analysis for the ductile–brittle transition by means of empirical ductility criteria ratios G/B and (C12–C44)/B as well as cleavage energy. The cleavage energy results indicated an intrinsic brittleness of the L21-Ni2AlTi phase and the L21-Ni2AlTi/BCC-Fe interface. Our analysis revealed that the intrinsic brittleness of L21-Ni2AlTi phase and L21-Ni2AlTi/BCC-Fe interface plays a vital role in determining the deformation behavior of the aged Fe–10Cr–5Ni–1Al–1Ti alloy.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Keyword

Cleavage energy

Ductility deterioration

First-principles calculations

L21-Ni2AlTi phase

L21-Ni2AlTi/BCC-Fe interface

Applied Physics

Tillämpad fysik

Publication and Content Type

ref (subject category)

art (subject category)