高氧含量低温钛合金的组织性能和低温变形机理

Microstructure, properties and cryogenic temperature deformation mechanism of a cryogenic titanium alloy with high-oxygen

摘要:

本文研究了不同氧含量低温钛合金棒材的组织性能及低温变形行为，阐明了高氧含量合金的低温（20K）强韧化机制。经750℃退火后，低温钛合金棒材呈等轴态组织，β相弥散分布于等轴αp相颗粒间。950℃退火后，超低氧含量（0.07.wt%）棒材为魏氏组织，中、高氧含量棒材为双态组织。随氧含量升高，棒材的抗拉强度升高，高氧含量（0.16wt.%）棒材20K下最大抗拉强度为1686.42MPa，延伸率为10.96%，室温抗拉强度为838MPa，延伸率为19.0%，高于TA34合金（GJB9583）的性能指标。等轴组织中等轴αp相和弥散分布的β相无取向关系、αp/β相晶界对位错的阻碍成为提高低温强度的关键。高氧含量合金20K下通过柱面<a>和锥面<a>多系滑移的开动及层错、孪晶变形的共同作用保证低温塑性，突破了传统高氧含量对孪晶的抑制作用，硬取向晶粒形成的T型织构、位错在界面的堆积及交互作用保证了高的抗拉强度。

Abstract:

In this study, the microstructure, properties and cryogenic temperature deformation behavior of cryogenic titanium alloy bars with different oxygen contents was investigated, and the strengthening-toughning mechanism of cryogenic titanium alloy with high oxygen content has been revealed. After annealled at 750℃, the microstructue is equaxied α<sub>p</sub> phase with dispersed β phase. Due to the α/β phase trasformation temperature affected by the oxygen content, the microstructure of extral-low oxygen content alloy with 0.07wt.% is typical Widmanstatten microstructure with grain boundary α phase and lamellar α/β phase, and the media and high oxygen content is typical bimodal structure after annealled at 950℃. The ultimate tensile strength increase with increased oxygen content. The ultimate tensile strength of high oxygen content alloy at 20K is 1686.42MPa, and the corresponding elongation is 10.96%, while the ultimate tensile strength of high oxygen content alloy at 300K is 838MPa, and the corresponding elongation is 19.0%, which is better than the corresponding properties of TA34 alloy reported at GJB 9583. The deformation mechanism investigated finds that the discations strengthening of equaixed α<sub>p</sub> phase and β phase bounadry caused by the non-crystallographic orientation relationship of α<sub>p</sub> phase and β phase, which is the key factor of strength increase. As for the high oxygen content alloy with 0.16wt.%, the plasticity at 20K is obtained by the dislocations slip of prismatic <a> and pyramidal <a>, and the activation of stack facults and twins, which breakthrough the inhibition of twins deformation by high oxygen content, and the dislocation accumulated at boudaried and interacted in α phase can improve ultimate tensile strength.