Study on Microstructure and Mechanical Properties of Laser Metal Deposition Near β Titanium Alloy
The microstructure and tensile properties at room temperature of the laser additive manufacturing Ti55511 titanium al-loy are studied,the grain morphologies and crystallographic texture of the as-deposited and heat treated Ti55511 titanium alloy are characterized,and the effects of different annealing temperatures on plasticity of the laser additive manufactured Ti55511 ti-tanium alloy are analyzed.The results indicate that the as-deposited Ti55511 titanium alloy consists of coarse β grains,and theβ grains grow alternately in the form of columnar and equiaxed grains,presenting a bamboo-like morphology.In the as-deposi-ted Ti55511 titanium alloy,the α lamellae precipitated from the β matrix provides a large number of interfaces,effectively hin-dering the movement of dislocations,and allows the alloy having high strength and low plasticity.The yield strength and tensile strength of the alloy annealed at 580 ℃ does not show significant changes,and the elongation increases to a certain extent.When the annealing temperature increases to 620℃,the yield strength and tensile strength of the alloy reduce,still greater than 1 000 MPa,and the elongation significantly increases.Therefore,the size and volume fraction of the α grains can be regu-lated through the annealing heat treatment to improve the strength and toughness balance of the alloy.When the stress is parallel to the Z deposition direction,the yield strength and tensile strength of the specimen are slightly lower than those of the specimen whose stress is perpendicular to the Z deposition direction,and the elongation is significantly higher than that of the specimen whose stress is perpendicular to the Z deposition direction.
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