Crystal plasticity aspects of a lamellar intermetallic microstructure
- Univ. for Mining and Metallurgy, Leoben (Austria)
- Vienna Univ. of Technology, Vienna (Austria)
Two-phase TiAl intermetallics consisting of {gamma} (TiAl) and {alpha}{sub 2} (Ti{sub 3}Al) lamellae possess mechanical properties which significantly differ from that of single-phase alloys. There are many experimental results of polysynthetically twinned (PST) TiAl crystals, which contain only a single set of lamellae with a specific orientation. Their yield stress at room temperature depends strongly on the angle {theta} between the orientation of the lamellae and the load axis. Furthermore, when compression loads are applied in the direction of the lamellae some sort of {open_quote}microbuckling{close_quote} could be observed, especially at high temperature during the primary forming process. In the paper this nonlinear anisotropic behavior is simulated by micromechanical computational methods with regard to finding a constitutive law for a polycrystal with lamellar grains. The modeling is based on the unit-cell techniques using the finite element method. Because of the orientation relationship of (111){sub {gamma}} {parallel} (0001){sub {alpha}2} and {l_angle}1{rvec 1}0{r_angle}{sub {gamma}} {parallel} {l_angle}11{rvec 2}0{r_angle}{sub {alpha}2}, is necessary to use crystal plasticity. The major deformation modes of the -Y phase at room temperature are ordinary slip along (110) and deformation twinning, i.e., true twinning of the (111){l_angle}11{rvec 2} type. These two modes are simulated in the unit-cell analyses. Using the micromechanical models, stress-strain curves are calculated for orientation angles {theta} varying in the range of 0{degrees} {le} {theta} {le} 90{degrees}, and the computed yield stresses are compared with experimental results. The {open_quote}microbuckling{close_quote} of the lamellae under compression loading is studied as well.
- OSTI ID:
- 175339
- Report Number(s):
- CONF-950686-; TRN: 95:006111-0297
- Resource Relation:
- Conference: Joint applied mechanics and materials summer meeting, Los Angeles, CA (United States), 28-30 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of AMD - MD `95: Summer conference; PB: 520 p.
- Country of Publication:
- United States
- Language:
- English
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