Microstructure and mechanical properties evolution of Ti-45Al-5Nb-0.3Y alloy by thermo-mechanical treatments
;yuyong chen;BaoHui Li
哈尔滨工业大学
Cite this article:
yuyong chen; BaoHui Li. Microstructure and mechanical properties evolution of Ti-45Al-5Nb-0.3Y alloy by thermo-mechanical treatments. Acta Metall Sin, 2008, 44(6): 757-763 .
Abstract Thermo-mechanical treatments, through combined action of hot forging and heat treatment, were performed on a Ti-45Al-5Nb-0.3Y alloy to investigate their effect on the microstructure and mechanical properties of the alloy. As-forged Ti-45Al-5Nb-0.3Y alloy is comprised of a large number of dynamic recrystallization (DRX) γ grains, curved and broken lamellae, and a small amount of remnant lamellae. The DRX γ grain size reaches 1~2μm. The deformed regions contained lots of dislocations and a little deformation twinning. As-forged Ti-45Al-5Nb-0.3Y alloy presents better tensile properties in comparison to as-cast material at room temperature. The ultimate tensile strength of as-forged alloy is about 708.1MPa and the elongation is about 0.95%. The fine duplex (DP), near lamellar (NL) and fully lamellar (FL) microstructures are obtained by further heat treatment. These microstructures have better room temperature ductility. The DP microstructure with lamellar colony size of about 20µm and lamellar volume fraction of about 60% is obtained by 1320℃/30min/FC. The microstructure has the highest ductility of about 1.9% and ultimate tensile strength of about 658.9MPa, and shows the transgranular and intergranular cracks. The NL microstructure with lamellar colony size of about 60µm and lamellar volume fraction of about 95% is obtained by 1340℃/30min/FC. The microstructure has the ductility of about 1.75% and ultimate tensile strength of about 690.2MPa, and mainly shows the transgranular cracks. The FL microstructure with lamellar colony size of about 40µm is obtained by 1370℃/15min/FC. The microstructure has the ductility of about 1.5% and highest ultimate tensile strength of about 715.1MPa, and shows the transgranular cracks.
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