PHASE COMPOSITION AND TRANSFORMATION STRESS OF PRIMARY LAMELLAR STRUCTURE IN γ-TiAl-BASED DUPLEX ALLOY DURING ISOTHERMAL DECOMPOSITION
WANG Jijie;ZONG Yaping;QIN Gaowu; HAO Shiming (School of Materials and Metallurgy; Northeastern University; Shenyang 110006)
Cite this article:
WANG Jijie;ZONG Yaping;QIN Gaowu; HAO Shiming (School of Materials and Metallurgy; Northeastern University; Shenyang 110006). PHASE COMPOSITION AND TRANSFORMATION STRESS OF PRIMARY LAMELLAR STRUCTURE IN γ-TiAl-BASED DUPLEX ALLOY DURING ISOTHERMAL DECOMPOSITION. Acta Metall Sin, 1998, 34(5): 538-544.
Abstract During isothermal decomposition of the supersaturated α2 phase in Ti-45%Al alloy at 950℃, the volume fractions of the decomposed γ phase and the lattice parameters of both α2 and γ phases have been investigated by X-ray diffraction. The results show that α2 phase in the primary lamellar microstructure (PLMS) is a metastable phase, and its composition should be identified by the tangency point on the common tangent of metastable α2 and γ phase free-energy curves. This composition is very important in calculation of free energy of the alloy and the driving force of discontinuous coarsening (DC). There exists transformation stress inside the original α grains at the direction perpendicular to PLMS which is a compress stress of about 50 MPa and will greatly affect the microstructure of the alloy.
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