TB18超高强韧钛合金显微组织中白斑研究

Research on White Blocks of TB18 Ultra-High Strength and Toughness Titanium Alloys

摘要:

针对一种高Mo当量亚稳β超高强韧钛合金TB18，在两相区锻造、β区固溶时效后显微组织中的白斑进行了系统研究。通过力学性能测试、显微组织观察和进一步热处理试验，分析白斑的形成机制和消除白斑可采取的措施。结果表明，TB18钛合金中的白斑是没有任何α相析出的β基体，其硬度低、塑性高、冲击韧性高。白斑形成的原因与合金中β稳定元素的分布无关，主要是锻造工艺引起的。可以通过优化锻造工艺或增加固溶度、预时效、延长时效时间等热处理手段从宏观组织上弱化或消除白斑，但是如果从更精细的组织考虑，TB18钛合金中白斑无法完全消除，只能从尺寸上减小，这是由合金性质决定。本研究结果对TB18合金制备工艺改进和组织优化具有基础指导，对同类合金的显微组织和性能分析也有重要的借鉴意义。

Abstract:

The white blocks of TB18 high Mo equivalent metastable β ultra-high strength and toughness titanium alloy were studied. The alloy which was forged in the two-phase region and then solid solution and aging treatment in β region. The formation mechanism and elimination methods of white blocks were analyzed by mechanical property testing, microstructure observation, and further heat treatment experiments. The results indicate that the white blocks in TB18 titanium alloy are β matrix without any precipitation of α phase, with low hardness, high plasticity, and high impact toughness. The reason for the formation of white blocks is not related to the distribution of β-stable elements in the alloy, but mainly caused by the forging process. White blocks can be weakened or eliminated from the macroscopic structure by optimizing forging or heat treatment processes, such as increasing solubility, pre-aging, and extending aging time. However, from a more detailed microstructure analysis, the white blocks in TB18 titanium alloy cannot be completely eliminated but can only be reduced in size, which is determined by the characteristics of the TB18 alloy. The results of this study have a fundamental guiding role in improving the preparation process and optimizing the microstructure of TB18 alloy, and also produce important reference significance for the microstructure and performance analysis of similar alloys.