Microstructure and Plastic Deformation of Orthorhombic Titanium Aluminides Ti_2AlNb. III. Formation of Transformation Twins upon the B2 -> O Phase Transformation

摘要

X-ray diffraction and transmission electron microscopy were used to study the O-phase formation in the Ti-25.6 percent Al-13.9 percent Nb-0.3 percent Mo-0.3 percent Zr alloy upon the B2 -> O phase transformation. The formation of pseudotwins is shown to be possible in the B2 phase in the Ti-Al-Nb alloys. It is found that the O phase upon the B2 -> O phase transformation does not undergo twinning, and all twins observed in the alloy belong to the intermediate metastable B19 phase. The orthorhombic O phase is formed upon ordering inside the B19-phase twins and save their boundaries.