近α型高温钛合金富氧燃烧组织特征及形成机理研究

Characteristics and Formation Mechanism of Near α Type High Temperature Titanium Alloy Combustion Microstructure Under Oxygen Enriched Conditions

摘要:

采用摩擦氧浓度实验方法点燃近 α 型TA19钛合金，获得富氧条件下临界着火和扩展燃烧后的着火损伤试样，结合扫描电子显微镜、能谱分析、透射电子显微镜和X射线衍射分析等手段研究燃烧产物的相组成、燃烧组织特征及形成机理。结果表明：TA19钛合金临界着火产物主要有TiO、Ti3O、金红石型和锐钛矿型TiO2，起始燃烧温度在500℃左右；扩展燃烧产物主要有TiO和金红石型TiO2，结合熔凝区形成的四方结构ZrO2判断持续燃烧温度在1170℃以上。从燃烧表面到钛合金基体可分为四个区域：燃烧区、熔凝区、热影响区和过渡区。临界着火时在熔凝区形成富O的Zr固溶体、富O的 α-Ti 固溶体和富Al/Sn/Mo的 β 相；在热影响区形成大量富O的 α-Ti 固溶体和少量富Al/Sn/Mo的 β 相。扩展燃烧时在熔凝区形成富O的Al固溶体，富O的Zr固溶体，富O的 α-Ti 固溶体和富Al/Sn/Mo的 β 相；在热影响区形成大量富O的 α-Ti 固溶体和少量富O和Zr的 β 相，两者构成致密的层状组织阻止了O的向内扩散，同时也阻止了Ti的向外扩散。TA19钛合金在燃烧过程中首先扩散到熔凝区界面前沿的是元素Zr，其次为Al，这与TA15钛合金燃烧过程中Al先扩散到熔凝区界面前沿有差异，其原因可能是由于TA19钛合金中的Zr含量是TA15钛合金Zr含量的2倍，Zr的活度更高。近 α 型高温钛合金的主要燃烧机理是富O固溶体的形成，从组织角度，较高的等轴相含量有利于固溶更多的O；从合金成分角度，适当控制Ti、Al、Zr元素含量有利于获得致密的富O固溶体。

关键词:近 α 型钛合金;燃烧组织;合金元素;燃烧机理

Abstract:

TA19 titanium alloy was ignited by friction oxygen concentration method, and two ignition damage samples after critical ignition and sustained combustion under oxygen enriched conditions were obtained. The phase composition, microstructure morphology and its formation mechanism of TA19 titanium alloy combustion products were studied by scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD). Results show that: The critical ignition products of TA19 titanium alloy mainly include TiO, Ti3O, rutile type and anatase type TiO2, and the initial combustion temperature is about 500℃. While the sustained combustion products of TA19 titanium alloy mainly include TiO, rutile type TiO2. Combined with the tetragonal structure ZrO2 formed in the fusion zone, the continuous combustion temperature is judged to be above 1170℃.Four distinct zones form from the combustion surface to the alloy matrix, and they are in the sequence of combustion zone, fusion zone, heat-affected zone and transition zone. During critical ignition, Zr solid solution rich in O, α-Ti solid solution rich in O and β phase rich in Al/Sn/Mo are formed in the fusione zone; A large amount of α-Ti solid solution rich in O and a small amount of β phase rich in Al/Sn/Mo are formed in the heat-affected zone. During sustained combustion, Al solid solution rich in O, Zr solid solution rich in O, α-Ti solid solution rich in O and β phase rich in Al/Sn/Mo are formed in the fusion zone; A large amount of α-Ti solid solution rich in O and a small amount of β phase rich in O and Zr are formed in the heat affected zone, finally they form a dense layered structure that prevents the inward diffusion of O and outward diffusion of Ti. In the combustion process of TA19 titanium alloy, the element Zr first diffuses into the interface of the fusion zone, followed by Al. This is different from that Al first diffuses to the interface of the fusion zone during the combustion of TA15 titanium alloy. The reason may be that the Zr content in TA19 titanium alloy is twice that in TA15 titanium alloy, and the activity of Zr is higher. The main combustion mechanism of near α type titanium alloy is the formation of O- rich solid solution. From the perspective of microstructure, higher equiaxed phase content is conducive to the dissolution of oxygen; From the point of view of alloy composition, proper control of the content of Ti, Al and Zr is beneficial to obtain dense O-rich solid solution.

Key words:near α type titanium alloy; burning microstructure; alloying elements; combustion mechanism