Abstract: Precipitation behavior of α phase and mechanical properties of Ti-1300 alloy after solution treatment followed by aging with low heating rate were investigated.The microstructure and mechanical properties of the Ti-1300 alloy with different solution treatment temperatures were observed and tested by means of SEM,TEM and tensile testing.The results show that when the solid solution treatment temperature is decreased from 820 ℃ to 790 ℃,the size of α_p (primary α phase) changes a little,while the area fraction of α_p increases from 0.8% to 6.7%.Subsequently,aging at 500 ℃ for 4 h with the heating rate of 4 ℃/min results in that the length of α_s (secondary α phase) increases from 0.098 μm to 0.440 μm.In addition,the decrease of solution treatment temperature increases the strengh and platisity of the alloy,and resulting in that the tensile fracture changes from intergranular brittle fracture to dimple-type ductile fracture.The tensile strength of the specimen solution-treated at 820 ℃ is 1358 MPa with platisity below 2%.While solution treated at 790 ℃,an excellent combination of strenth (1548 MPa) with platisity (10.2%) is obtained,the main reason of which is the high content of primary α phase in micrometer scale,and the lamella-shaped α_s precipitated in the matrix has significant strengthening effect.

Key words: Ti-1300 alloy, solid solution treatment, α phase, mechanical properties