TC11钛合金中α″相和α′相的组织演变和显微硬度

Microstructure Evolution of α"-Phase and α’-Phase and Microhardness of TC11 Titanium Alloy

研究了TC11钛合金中α"相和α'相的显微组织转变和显微硬度。金相显微组织观察和X射线衍射分析的结果表明:随着固溶温度的提高α"相逐渐向α'相的晶体结构转变,α相、α"相和α'相的显微组织演变规律为:α+α",α+α"+α',α+α',α'。显微硬度测试的结果表明:在935~995℃固溶后显微硬度随着温度的提高先增大后减少,在985℃固溶后显微硬度达到峰值。综合分析显微组织影响合金显微硬度的机理:在935~985℃固溶后α'片层的厚度和间距变化的幅度小,β转变组织长大缓慢,在β转变组织中先后析出α"和α'相,随着固溶温度的提高α'片层的含量随之提高产生了相变强度效果,使其显微硬度提高;在985~995℃固溶后α'片层的厚度和间距明显增大,β转变组织变粗大,α"相消失,α'相的含量降低,相变强化的效果减弱,使β转变组织的显微硬度降低。

The effect of solution treatment temperature (STT)(ranging from 935°C to 995°C) on the microstructure evolution of α"-phase,α'-phase and microhardness of TC11 titanium alloy were investigated systematically by means of optical microscope, electron microscope with energy dispersive spectroscope, X-ray diffractometer and microhardness tester. Results show that the crystal structure of α"-phase gradually correspond to the crystal structure of the α' phase, and the phase composition of TC11 alloy changes with increasing STT (α+α",α+α"+α',α+α',α'). Microhardness of the alloy solution treated in the temperature range from 935~985°C increased with the solution temperature, whereas the microhardness reduced for further increase of solution temperature up to the range of 985~995°C. Microstructural features resulting from different STTs were correlated with corresponding microhardness values. With the increment of STT the microhardness increased, because the thickness and spacing of α'-lamellae increased slowly and the β-transformed structure grew up slowly. Besides, due to phase transition strengthening (PTS) the α"-phase and α'-phase are precipitated in the β-transformed structure, and the α'-lamellae contents in the β-transformed microstructure increased, eventually reaching a maximum at 985°C. Above 985°C the microhardness decreased, because the thickness and spacing of α'-lamellae increased significantly and the β-transformed structure became coarser at the expense of α'-phase and α"-phase contents.