Shin Su-Hong, Lee Dong-Geun
Department of Materials Science and Metallurgical Engineering, Sunchon National University, Sunchon 57922, Republic of Korea.
Materials (Basel). 2025 May 23;18(11):2448. doi: 10.3390/ma18112448.
Ti-2Al-9.2Mo-2Fe (2A2F) alloy is a low-cost β-Ti alloy in which the expensive β-stabilizing elements (Ta, Nb, W, Ni) are replaced with relatively inexpensive Mo and Fe for use in low-cost applications in various industries. The 2A2F alloy exhibits excellent mechanical properties such as high specific strength and low elastic modulus compared to conventional steel alloys but is prone to brittleness owing to the formation of the ω phase when heat-treated at relatively low temperatures. Therefore, an appropriate aging treatment should be performed to control the precipitation of the isothermal ω phase and secondary α phase. This study aims to derive the appropriate aging-treatment conditions following a solution treatment at 790 °C for 1 h, which is below the β-transus temperature of 815 °C. The aging treatments are conducted at holding temperatures in the range of 450-600 °C and holding times between 1 and 18 h. At relatively low aging temperatures of 450 °C and 500 °C, the precipitation of the isothermal ω phase resulted in significantly high hardness and compressive strength. As the aging temperature and holding time increased, the ω phase gradually transformed into the secondary α phase, leading to a balanced combination of strength and ductility. However, at excessively high aging temperatures and prolonged durations, excessive precipitation and growth of secondary α phases occurred, which caused a reduction in hardness and compressive strength, accompanied by an increase in ductility. In this study, the effects of precipitation evolution on mechanical properties such as tensile strength and hardness under various heat treatment conditions were comparatively analyzed.
Ti-2Al-9.2Mo-2Fe（2A2F）合金是一种低成本的β钛合金，其中昂贵的β稳定元素（Ta、Nb、W、Ni）被相对便宜的Mo和Fe取代，用于各行业的低成本应用。与传统钢合金相比，2A2F合金具有优异的机械性能，如高比强度和低弹性模量，但在相对低温下进行热处理时，由于ω相的形成而容易变脆。因此，应进行适当的时效处理以控制等温ω相和次生α相的析出。本研究旨在得出在低于815℃的β转变温度下于790℃固溶处理1小时后的合适时效处理条件。时效处理在450 - 600℃的保温温度范围和1 - 18小时的保温时间下进行。在450℃和500℃的相对较低时效温度下，等温ω相的析出导致硬度和抗压强度显著提高。随着时效温度和保温时间的增加，ω相逐渐转变为次生α相，从而实现强度和延展性的平衡组合。然而，在过高的时效温度和过长的保温时间下，次生α相发生过度析出和长大，导致硬度和抗压强度降低，同时延展性增加。在本研究中，对各种热处理条件下析出演变对拉伸强度和硬度等力学性能的影响进行了比较分析。
