氧化石墨烯对近α型高温钛合金非等温氧化行为的影响机理

Influence mechanism of graphene oxide on non-oxidation behavior of near-αhigh-temperature titanium alloy

摘要:

采用热重—差热分析仪对未添加氧化石墨烯（GO）和添加0.5 wt.% GO的近α型高温钛合金（Ti150）进行室温~1500 ℃ 的非等温氧化试验，分析氧化增重规律和氧化产物组织特征，揭示GO对非等温氧化行为的影响机理。结果表明：添加GO的Ti150钛合金的非等温氧化过程包括基本无氧化（≤800 ℃）、氧在α相缓慢溶解（800~1160 ℃）、氧在两相区加速溶解（1160~1300 ℃）、氧在β相快速溶解（1300~1330 ℃）和氧化层剧烈生长（1330~1500 ℃）等五个阶段，氧在β相的溶解和氧化层的生长是非等温氧化增重的主要原因；非等温氧化温度升高至1500 ℃ 时，添加GO的Ti150钛合金的氧化增重和氧化层厚度比未添加GO的合金分别降低10.8%和17.9%；GO提高Ti150钛合金的抗非等温氧化性的主要机理包括两个方面，一是GO提高了合金的β转变温度，推迟了氧在β相中的快速溶解，减少了氧的溶解量；二是GO细化了合金晶粒，增加了晶界数量，使Al和Sn离子更容易向外扩散形成连续致密的富Al2O3层和富Sn层，增强了对氧和金属离子的阻隔作用。

关键词:高温钛合金;氧化石墨烯;非等温氧化;氧化动力学;氧化机理

Abstract:

The non-isothermal oxidation tests ofthe near-α high-temperature titanium alloys (Ti150) without graphene oxide (GO) and with 0.5 wt.% GO were carried out at room temperature ~1500 ℃ by thermogravimetry-differential scanning calorimetry method. The influence mechanism of GO on non-isothermal oxidation behavior was revealed by analyzing the oxidation mass gain laws and the microstructure characteristics of oxidation products. The results showed that the non-isothermal oxidation process of Ti150 alloy with GO included almost no oxidation (≤800 ℃), slow dissolution of oxygen in α phase (800~1160 ℃), accelerated dissolution of oxygen in two-phase region (1160~1300 ℃), rapid dissolution of oxygen in β phase (1300~1330 ℃), and violent growth of oxide scale (1330~1500 ℃) five stages. The dissolution of oxygen in β phase and growth of oxide scale were the main reasons for the non-isothermal oxidation mass gain. After non-isothermal oxidation to 1500 ℃, the non-isothermal oxidation mass gain and oxide scale thickness of Ti150 alloy with GO were 10.8% and 17.9% lower than those without GO, respectively. The main mechanism of GO improving the non-isothermal oxidation resistance was that the beginning temperature of rapid dissolution of oxygen in β-Ti was delayed due to the higher β-transus temperature of Ti150 alloy with GO, which resulted in the decrease of oxygen solution, and the finer grain made the Al2O3-rich oxide layer and the Sn-rich layer more continuous and dense, which were more effective barriers to ion diffusion.

Key words:High-temperature titanium alloys;Graphene oxide;Non-isothermal oxidation;Oxidation kinetics;Oxidation mechanism