Mechanical properties and strengthening of a Ni-25Mo-8Cr alloy containing Ni{sub 2}(Mo,Cr) precipitates

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(96)00092-4· OSTI ID:417833

Kumar, M; Vasudevan, V K ^[1]

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1. Univ. of Cincinnati, OH (United States). Dept. of Materials Science and Engineering

The mechanical properties and mechanisms of deformation and strengthening of Haynes Alloy 242{sup tm}, a nominal Ni-25Mo-8Cr (in wt%) containing Ni{sub 2}(Mo,Cr) precipitates in a face-centered cubic matrix, are reported. Both solution treated, as well as aged samples (550--750 C, 1--1,200 h) were deformed to permanent strains of 1 and 6% in compression and to failure in tension. The deformation structures were observed by transmission electron microscopy. A two-fold increase in strength and tremendous strain hardening are observed as the short-range (SRO) to long-range ordering (LRO) transformation proceeds, although ductility remains high even in well-aged samples. Major contribution to strengthening and strain hardening comes from the precipitation of a high volume fraction of Ni{sub 2}(Mo,Cr) precipitates, with hardening in the solution treated samples and those aged for short periods being associated with the presence of SRO in the matrix. A transition in deformation mode, from glide of unit dislocations in planar arrays to profuse twinning, is observed as a function of aging time and imposed strain, twinning being observed in samples containing Ni{sub 2}(Mo,Cr) precipitates. A semi-quantitative model developed on the basis of precipitate size and mode of deformation (shearing, twinning, bypassing) is able to satisfactorily account for this transition. A presentation and discussion of these results, as well as those of the mechanisms of strengthening and strain hardening, are provided.

• OSTI ID: 417833
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 12 Vol. 44; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGING
CHROMIUM ALLOYS
DEFORMATION
DISLOCATIONS
MECHANICAL PROPERTIES
MOLYBDENUM ALLOYS
NICKEL ALLOYS
PRECIPITATION
STRAIN HARDENING
STRAINS
TRANSMISSION ELECTRON MICROSCOPY
TWINNING