Titanium alloy is an alloy composed of other elements based on titanium ,which has two isomorphic crystals: it is isomeric, the melting point is 1668, below 882, a hexagonal lattice structure, known as alpha-titanium; above 882, a body-centered cubic lattice structure, known as beta-titanium. Titanium alloys with different microstructures were obtained by adding appropriate alloying elements according to the different characteristics of the two structures.
The commonly used heat treatment methods are annealing, solution and aging treatment.
Annealing is to eliminate internal stress and improve plasticity and tissue stability, so as to achieve better comprehensive properties. Usually, the annealing temperatures of a alloy and (a + beta) alloy are 120 ~ 200 below (a + beta) beta phase transition point; solid solution and aging treatment are rapid cooling from high temperature region to obtain martensite alpha phase and metastable beta phase, and then these metastable phases are decomposed by holding in the middle temperature region to obtain fine dispersed second phase such as alpha phase or compound. The aim of alloy strengthening is achieved. Usually (a + beta) alloys are quenched at (a + beta) - beta phase transition point below 40 ~ 100, and metastable beta gold at (a + beta) - beta phase transition point above 40 ~ 80. The aging temperature is generally 450~550 degrees.
It is concluded that the heat treatment process of titanium alloys can be summarized as follows:
(1) eliminate stress annealing: the purpose is to eliminate or reduce the residual stresses generated during machining. Prevent chemical erosion and reduce deformation in some corrosive environments.
(2) Complete annealing: the purpose is to obtain good toughness, improve processing performance, is conducive to reprocessing and improve the size and structure stability.
(3) Solution treatment and aging: the aim is to improve the strength of the alloy and the stable beta-titanium alloy can not be strengthened heat treatment