Twinning in L1[sub 0] type Fe-Pt alloys

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90078-7· OSTI ID:6935727

Gao, Y Q; Whang, S H ^[1]

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1. Polytechnic Univ., Brooklyn, NY (United States). Dept. of Materials Science and Engineering

Previously, twin systems of [111] <112> were reported in L1[sub 0] TiAl. No pseudo twinning was observed in TiAl. This is probably due to the fact that the pseudo twins, [111], [211] or [121], result in L1[sub 1] like structure which has a higher energy in TiAl. Nevertheless, it was suggested that the pseudo-twinning might be possible at high temperatures where a disordering occurs and the pseudo-twin energy becomes small. In current experiments, FePt alloy which was deformed at 600 C didn't show pseudo twinning. Since the order-disorder transformation occurs at 1,300 C, it is still likely that a high degree of disordering may occur above 1,100 C. Relatively easy twinning in FePt as compared to TiAl may be explained from two reasons. First, FePt may be characterized as having a metallic bonding while TiAl as having a covalent bonding. Also, the heat of formation indicates that a strong bonding exists in TiAl. The heat of formation for FePt is [minus]25 kJmol[sup [minus]1] (1,123 K) and that of TiAl is [minus]36 kJ[sup [minus]1]. Second, the twinning shear for FePt is 0.63 compared to 0.96 in TiAl. For these reasons, twinning shear in FePt would requires less energy than that required in TiAl.

• DOE Contract Number: FG02-93ER45499
• OSTI ID: 6935727
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:11; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals &amp; Alloys-- Structure &amp; Phase Studies
ALLOYS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
DATA
DEFORMATION
EXPERIMENTAL DATA
FCC LATTICES
INFORMATION
IRON ALLOYS
NUMERICAL DATA
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
TWINNING