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Study on High Temperature Strength and Deformation Mechenism of Ti2 AlN/TiAl Composites

Author: GuoLinLin
Tutor: SunDongLi
School: Harbin Institute of Technology
Course: Materials Science
Keywords: Ti2AlN/TiAl composite High-temperature strength Lamellar Deformation mechanism
CLC: TB331
Type: Master's thesis
Year: 2010
Downloads: 62
Quote: 1
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Abstract


This article by powder metallurgy method of preparation of a Ti-47Al alloy, 20% and 50% volume fraction of Ti 2 AlN phase Reinforced TiAl composite material, by heat treatment to obtain a homogeneous lamellar structure. Gleeble-1500D thermal simulation testing machine to test the three materials under different temperatures and strain rate true stress - true strain curves and high temperature compression strength, using optical microscope, scanning electron microscopy, transmission electron microscopy before and after the compression deformation Microstructure calculated under different temperature deformation activation energy, to discuss strengthening effect of the variation of the high temperature compression strength under different deformation conditions and composite materials, explore the hot deformation behavior and deformation mechanism. Studies have shown that, within the selected temperature (800 1 100 ℃) and strain rate (0.001 0 .1 s -1 ), Ti- 47Al alloy and Ti 2 of AlN / TiAl composite material at high temperature compression true stress - true strain curve can be divided into three stages: elastic deformation stage, work hardening stage and stiffening of the softening stage. Stress peak in the curve is defined as the compression strength, and its value as the temperature increases and down, is increased as the strain rate increases. Two intervals of the high temperature and high strain-rate and low temperature and strain rate, the composite material having a higher strength. 1100 ℃, strain rate 0.1s -1 conditions, the compressive strength of composites reach 618.4MPa increased by 50.24% relative to the Ti-47Al matrix alloy. The organizational analysis showed that the temperature compression process lamellae decreases the vertical and the angle between the direction of deformation, grain internal lamellar bending. Ti-47Al alloy cryogenic deformation is grain boundary sliding and grain interior lamellae bent; temperature compression deformation mechanisms for intragranular bit wrong slip and grain boundary sliding; the Ti 2 AlN / The compressive deformation mechanisms in TiAl composites the dislocation glide intragranular bit, Ti 2 AlN play a role impede dislocation movement; calculated Ti-47Al alloy in 800 1 100 ℃, 0.001 of 0 .1 s -1 within the deformation activation energy average of 398.6KJ/mol, 20% and 50% Ti 2 AlN / TiAl composites at 800 1 the deformation activation within the range of 100 ° C. the average strain rate and strain rate 0.001 0 .01 s -1 < / sup> range deformation activation energy were 566.8KJ/mol and 547.8KJ/mol the <.1 of the / sup> s in 0.01 0 -1 within the deformation activation energy for 334.1 KJ / mol and 352.0KJ/mol. Transmission electron microscopy analysis revealed that the Ti-47Al alloy and Ti 2 of AlN / TiAl composite deformation lamellae internal bit wrong mainly distributed in the α2 phase, γ-phase internal dislocation density smaller lamellar deformation mode is determined mainly by the deformation of α2 phase mode, temperature compression deformation the material occurred dynamic recovery and recrystallization leading to strain softening.

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