On the strengthening and embrittlement mechanisms of an additively manufactured Nickel-base superalloy
Artikel i vetenskaplig tidskrift, 2020

The γ′ phase strengthened Nickel-base superalloy is one of the most significant dual-phase alloy systems for high-temperature engineering applications. The tensile properties of laser powder-bed-fused IN738LC superalloy in the as-built state have been shown to have both good strength and ductility compared with its post-thermal treated state. A microstructural hierarchy composed of weak texture, sub-micron cellular structures and dislocation cellular walls was promoted in the as-built sample. After post-thermal treatment, the secondary phase γ′ precipitated with various size and fraction depending on heat treatment process. For room-temperature tensile tests, the dominated deformation mechanism is planar slip of dislocations in the as-built sample while dislocations bypassing the precipitates via Orowan looping in the γ′ strengthened samples. The extraordinary strengthening effect due to the dislocation substructure in the as-built sample provides an addition of 372 MPa in yield strength. The results of our calculation are in agreement with experimental yield strength for all the three different conditions investigated. Strikingly, the γ′ strengthened samples have higher work hardening rate than as-built sample but encounter premature failure. Experimental evidence shows that the embrittlement mechanism in the γ′ strengthened samples is caused by the high dislocation hardening of the grain interior region, which reduces the ability to accommodate further plastic strain and leads to premature intergranular cracking. On the basis of these results, the strengthening micromechanism and double-edge effect of strength and ductility of Nickel-base superalloy is discussed in detail.

Mechanical property

Nickel-base superalloy

Laser powder-bed-fusion

γ′ phase

Cellular structure

Författare

Jinghao Xu

Linköpings universitet

Hans Gruber

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Robert Boyd

Linköpings universitet

Shuang Jiang

Linköpings universitet

R. Lin Peng

Linköpings universitet

JJ Moverare

Linköpings universitet

Materialia

25891529 (eISSN)

Vol. 10 100657

Nya materiallösningar för defektfri additiv tillverkning av svårsvetsade Ni-baserade legeringar

VINNOVA, 2018-06-01 -- 2021-05-31.

Ämneskategorier

Bearbetnings-, yt- och fogningsteknik

Annan materialteknik

Metallurgi och metalliska material

DOI

10.1016/j.mtla.2020.100657

Mer information

Senast uppdaterat

2020-05-20