TiFe Precipitation Behavior and its Effect on Strengthening in Solution Heat-Treated Ti-5Al-3.5Fe During Isothermal Aging

Metals

JongWoo Won¹  KaRam Lim¹  Yong-Taek Hyun¹  Hye-Jeong Choe¹  Seog-Young Yoon² 

[1] Metal Materials Division, Korea Institute of Materials Science, Changwon 51508, Korea;School of Materials Science and Engineering, Busan National University, Pusan 46241, Korea;

关键词: titanium alloys;    precipitates;    phase transformation;    hardness;   

DOI  :  10.3390/met8110875

来源: DOAJ

【 摘 要 】

We investigated the TiFe precipitation behavior of solution heat-treated Ti-5Al-3.5Fe during isothermal aging, quantified the effect of precipitation on strengthening by evaluating the hardness, and compared it to the effect of Ti₃Al precipitation in Ti-6Al-4V. TiFe precipitates formed both at grain boundaries (GBs) and within the grain matrices. Phase transformation from the β to α phase also occurred during isothermal aging; this transformation generated lamellar interphase boundaries between the transformed α phase and remaining β phase in prior β grains. These interphase boundaries enabled the formation of in-grain TiFe precipitates by acting as a nucleation site. GB precipitation did not require prior β → α phase transformation to generate nucleation sites (i.e., interphase boundaries), so TiFe precipitation could occur immediately upon isothermal aging. Thus, GB precipitation proceeded more quickly than in-grain precipitation; as a result, precipitates were larger and more spherical at the GBs than in grains. The strengthening behavior exhibited by TiFe precipitation differed obviously from that caused by Ti₃Al precipitation in Ti-6Al-4V because of its differing precipitation kinetics and related microstructural evolution.

【 授权许可】

Unknown