Effects of carbon content and ausaging on [gamma] [leftrightarrow] [alpha][prime] transformation behavior and reverse-transformed structure in Fe-Ni-Co-Al-C alloys

Journal Article · Sat Jan 01 04:00:00 EST 1994 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

OSTI ID:5264443

Ohtsuka, H; Kajiwara, S ^[1]

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1. National Research Inst. for Metals, Tokyo (Japan)

The effects of carbon content and ausaging on austenite ([gamma]) [leftrightarrow] martensite ([alpha][prime]) transformation behavior and reverse-transformed structure were investigated in Fe-32Ni-12Co-4Al and Fe-(26,28)Ni-12Co-4Al-0.4C (wt pct) alloys. The M[sub s] temperature, the hardness of [gamma] phase, and the tetragonality of [alpha][prime] increase with increasing ausaging time, and these values are higher in the carbon-bearing alloys in most cases. The [gamma] [r arrow] [alpha][prime] transformation behavior is similar to that of thermoelastic martensite; that is, the width of [alpha][prime] plate increases with decreasing temperature in all alloys. The [alpha][prime] [r arrow] [gamma] reverse transformation temperature is lower in the carbon-bearing alloys, which means that the shape memory effect is improved by the addition of carbon. The maximum shape recovery of 84 pct is obtained in Fe-28Ni-12Co-4Al-0.4C alloy when the ausaged specimen is deformed at the M[sub s] temperature and heated to 1120 K. There are two types of reverse-transformed austenites in the carbon-bearing alloy. One type is the reversed [gamma] containing many dislocations which were formed when the [gamma]/[alpha][prime] interface moved reversibly. The plane on which dislocations lie is (011)[sub [gamma]] if the twin plane is (112)[sub [alpha][prime]]. The other type of reverse-transformed austenite exhibits [gamma] islands nucleated within the [alpha][prime] plates.

• OSTI ID: 5264443
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 25:1; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
AUSTENITE
CARBON
CARBON ADDITIONS
COBALT ALLOYS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
ELEMENTS
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITE
METALLURGICAL EFFECTS
NICKEL ALLOYS
NONMETALS
PHASE TRANSFORMATIONS