Effect of hydrogen on phase and microstructure of Ti600 alloy

Abstract

Effects of hydrogen on microstructure characteristics and precipitation behavior have been investigated in Ti600 alloy hydrogenated at 750°C. Due to the precipitation of δ hydride and α″ martensite, X-ray diffraction (XRD) peaks of α phase shifted to lower angles and became broadened. XRD data showed that the addition of hydrogen expanded crystal lattice of α phase and lattice volume increased linearly in the range of 0 < C _H < 0.792 wt%. XRD, scanning electron microscopy, and transmission electron microscopy analysis revealed precipitation behavior of secondary α lamellar, α″ martensite and δ hydride. Compared to as-received one, microstructure of hydrogenated Ti600 alloy changed obviously. Equiaxed α phase decreased and even vanished with hydrogen contents increasing. Parallel fine lamellar structure appeared and the colonies were constructed by different orientation. Micro-hardness of hydrogenated Ti600 alloy increased with the increase of hydrogen concentration, and it was considered that interstitial solution strengthening, precipitation of δ hydride, and generation of defects were the major factors.

Keywords:

• near-α high temperature Ti600 alloy
• δ hydride
• silicide
• α″ martensite
• micro-hardness

Acknowledgments

The authors wish to thank the support from the Fund of Key Disciplinary of Material Processing Engineering (Xihua University) and the Key Program (No. Z1120117) in Xihua University and Department of Education Research Fund in China, Sichuan Province.