Fe含量对Ti5553合金α相析出响应与硬化行为的影响

摘要

利用混合元素烧结法制备含0、0.4、1.2和2.0 wt.％Fe的Ti5553合金.研究Fe元素对绝热ω相变、α 相析出长大以及时效硬化行为的影响规律.结果表明,2 wt.％Fe元素的加入可提高 β 相的稳定性,抑制绝热ω相析出.随着Fe含量增加,α 相析出孕育期变长,尺寸变小.α 相沿晶析出倾向增强,尤其是在炉冷时,Ti5553?2Fe合金形成明显的魏氏组织.随后,利用Pandat软件并结合经典动力学理论分析Fe含量对Ti5553合金 α 相析出长大行为的影响机制.硬度曲线表明,不同Fe含量合金的硬度均随时效时间延长先增加,6 h达到峰值后缓慢降低.Ti5553?2Fe合金具有最高的峰值硬度,这是Fe等合金元素点阵错配引起的固溶强化与细小 α 相析出引起的时效强化共同作用的结果.%Ti5553?xFe (x=0.4, 1.2, 2.0, wt.％) alloys have been designed and fabricated through BE (blended element) sintering to investigate the effect of Fe-addition on athermal ω-phase transformation, α-phase evolution and age hardening behavior. The results show that the formation of athermal ω-phase is fully suppressed in water-quenched specimens when Fe-addition is up to 2 wt.％. The relevant timescales of α formation during initial stages of aging indicate that incubation time increases with Fe-addition. Further aging results in continuous nucleation and growth of α-phase but finer intragranular α lamellae exhibit in Ti5553?2Fe alloy. In addition, the width and extent of grain boundary α-film increase slightly with incremental Fe-addition, especially in furnace cooling condition. Result of Vickers hardness manifests that Fe-addition leads to a strong hardening effect in both solution and aging treatment. The solid solution strengthening is quantitatively estimated by ab initio calculation based on the Labusch?Nabarro model. The evolution of α-precipitate is rationalized by Gibbs free energy. The prominent hardening effect of Ti5553?2Fe alloy is attributed to both large lattice misfit of β-matrix and fine α-precipitate distribution.