激光点火Ti-Al-Mo-Zr-Sn-W合金燃烧行为与组织

Combustion Behavior and Microstructure of Ti-Al-Mo-Zr-Sn-W Alloy After Laser Ignition

摘要:

采用激光点火实验结合超高温红外测温以及SEM、XRD和TEM等分析方法，研究典型Ti-Al-Mo-Zr-Sn-W合金（TC25G）在高温高速气流环境下的燃烧行为，并与TC11钛合金的阻燃性能进行比较，进而分析燃烧产物组织特征、晶体结构及形成机理。结果表明：在气流温度为200~400 ℃，气流速度为0~100 m/s范围内，高温高速气流能够促进TC25G钛合金持续燃烧，燃烧路径朝气流方向推进；TC25G钛合金的燃烧主要依靠氧的扩散与熔体移动所导致的燃烧区域扩展。基于合金燃烧产物组织与成分特点可以将其划分为燃烧区、熔凝区、热影响区等不同区域，燃烧过程组织特征的形成与合金元素行为及其与氧的选择性结合密切相关。燃烧区Ti的主要氧化产物为TiO和TiO₂，燃烧过程中形成的Mo、W元素的氧化混合物阻碍了熔体的移动，Al和Zr倾向于发生内氧化，Al₂O₃在ZrO₂表面析出并形成了氧化层组织，构成了保护性屏障，抑制了O向内扩散。熔凝区与热影响区界面处的元素富集能够提高固相侧的熔点，阻碍固-液界面的迁移。

Abstract:

The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy (TC25G) was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer, scanning electron microscope, X-ray diffractometer, and transmission electron microscope. The burn-resistant performance of TC25G and TC11 alloys was compared. Meanwhile, the microstructural characteristics, crystal structure, and formation mechanism of the combustion products of TC25G alloy were analyzed in detail. The results show that the high-temperature and high-speed air flow promotes combustion within the air flow temperature range of 200–400 °C and the air flow velocity range of 0–100 m/s. The combustion path advances along the direction of the air flow. The combustion of TC25G alloy mainly relies on the diffusion of the oxygen and the expansion of the combustion area caused by the movement of the melt. Based on the microstructure and composition of combustion product, it can be divided into the combustion zone, the melting zone, and the heat affected zone. During combustion, the formation of microstructures is closely correlated with the behavior of alloying elements and their selective combination with O. The major oxidation products of Ti are TiO and TiO₂. The oxides formed by Mo and W hinder the movement of the melt during the combustion. Al and Zr tend to undergo internal oxidation. Al₂O₃ precipitates on the surface of ZrO₂, forming a protective oxide layer that inhibits the inward diffusion of O. Moreover, the element enrichment at the interface between the melting zone and the heat affected zone increases the melting point on the solid side, hindering the migration of the solid-liquid interface.