选区激光熔化TB6钛合金α相析出和力学性能研究

Precipitation of α Phase and Mechanical Properties of TB6 Titanium Alloy Prepared by Selective Laser Melting

摘要:

采用选区激光熔化技术制备了TB6钛合金试样，研究了时效温度对合金显微组织和力学性能的影响。结果表明，选区激光熔化成形沉积态TB6合金的显微组织主要由柱状β相和等轴α相组成，固溶时效后析出晶内层片状或颗粒状α_P相及晶界α_GB相。随着时效温度的升高，α相尺寸逐渐减小，层片状α相体积分数降低，颗粒状α_p含量增加。拉伸性能测试结果显示，随时效温度提高，材料的抗拉强度降低而塑性明显提升。560 ℃时效试样的抗拉强度由520 ℃时效的1386.22 MPa降低到1129.00 MPa，而延伸率由520 ℃时效下的7.1%增至10.5%。研究发现，α相形貌和尺寸的变化影响了合金的强度与塑性，减少层片状α_L相的体积分数和增加颗粒状α_P相的体积分数有助于实现较好的强塑性匹配，提高时效温度可以降低层片状α_L相的体积分数，可改善材料的塑性。

Abstract:

The influence of aging temperature on the microstructure and mechanical properties of TB6 titanium alloy fabricated via selective laser melting (SLM) was investigated. The results show that the microstructure of SLMed TB6 titanium alloy predominantly consists of columnar β phase and equiaxed α phase, and the precipitation of lamellar or granular α_P phase and grain boundary α_GB phase occurs after solution treatment and aging. With the increase in aging temperature, the α phase is gradually diminished in size, the volume fraction of lamellar α phase is decreased, and the amount of granular α_P phase is increased. The tensile test results indicate that as the aging temperature increases, the tensile strength of the material decreases while its plasticity is significantly improved. The tensile strength of samples decreases from 1386.22 MPa (aged at 520 ℃) to 1129.00 MPa (aged at 560 ℃), whereas its elongation increases from 7.1% to 10.5%. It is concluded that changes in the morphology and size of the α phase significantly impact the strength and plasticity of the alloy. Reducing the volume fraction of lamellar α_L phase and increasing that of granular α_P phase improve the strong-plasticity matching. Elevating the aging temperature can decrease the volume fraction of lamellar α_L phase and enhance the plasticity of the material.