Cr含量对WMoNbCrTi高熵合金力学和抗氧化性能的影响

Effect of Cr Content on Mechanical Properties and Oxidation Resistance of WMoNbCrTi Hing-Entropy Alloy

摘要:

WMoNbTiCr难熔高熵合金具有优越的力学性能，是一种具有应用潜力的高温结构材料。在粉末冶金烧结制备过程中，WMoNbTiCr高熵合金中Cr与其他元素会发生反应形成Lave相，而Laves相对WMoNbTiCr高熵合金的力学和抗氧化性能有重大的影响。然而，Cr含量对WMoNbTiCr高熵合金力学性能和高温抗氧化性能的影响规律及其作用机理尚不清楚，待进一步研究。以W、Nb、Mo、Cr和Ti单质粉末为原材料，通过机械合金化对粉末进行高能球磨，采用放电等离子烧结技术制备了4种不同Cr含量的WMoNbCrTi高熵合金，同时探讨了Cr含量对WMoNbCrTi高熵合金物相组成、微观组织、室温力学性能及800 ℃高温抗氧化性能的影响。研究结果表明，随着Cr含量的增加，WMoNbTiCr合金维氏硬度、压缩断裂强度和压缩应变相应增加，其中20W20Mo20Nb20Ti20Cr高熵合金的硬度、断裂强度和应变均达到最大值，分别为9.73 GPa、2 116 MPa和5.1%。随着Cr含量的增加，WMoNbTiCr高熵合金的晶粒尺寸越来越小，合金压缩应变的增加主要归因于高熵合金晶粒细化效果。WMoNbTiCr高熵合金的固溶强化、Laves第二相强化和组织细化的综合效应，提高了合金的硬度和压缩断裂强度。另外，4种不同Cr含量的WMoNbCrTi高熵合金在800 ℃下氧化40 h后，合金表面均形成疏松多孔的氧化膜，并且该氧化膜容易脱落，说明Cr含量的增加只能稍微改善WMoNbCrTi高熵合金在800 ℃下的抗氧化性能。Cr含量对WMoNbTiCr高熵合金力学性能和高温抗氧化性能的影响研究，为难熔高熵合金的发展提供了实验基础和理论指导。(专精特新·特殊环境材料服役行为专辑十五之十)

Abstract:

The WMoNbCrTi refractory high entropy alloy， which has excellent mechanical properties， is a promising high temperature structural material. Laves phases are formed in WMoNbCrTi alloy during the preparing process. The Laves phases have a significant influence on the mechanical properties and oxidation resistance of WMoNbCrTi alloy. However， the effect of Cr content on the mechanical properties and high temperature oxidation resistance of WMoNbCrTi alloy is not yet clear， which needs to be further studied. In this paper， four kinds of high entropy alloy powders with different Cr contents were prepared by using W， Nb， Mo， Cr and Ti as raw materials. Refractory WMoNbTiCr HEAs with different Cr content were prepared by mechanical alloying followed by spark plasma sintering. The effects of chromium content on the phase composition， microstructure， room temperature mechanical properties and oxidation resistance at 800 ℃ of WMoNbTiCr HEAs were investigated. As the content of Cr increase， the Vickers hardness， compressive fracture strength， and compressive strain of the WMoNbTiCr HEAs also increase. The 20W20Mo20Nb20Ti20Cr alloy exhibits the corresponding maximum values of 9.73 GPa， 2 116 MPa， and 5.1% for the 20Cr alloy， respectively. With the increase of Cr content， the grain size of WMoNbTiCr alloy becomes smaller and smaller. The increasing compressive strain are mainly attributed to the grain refinement. However， the solid solution strengthening， the Laves phase strengthening， and microstructure refinement resulted in an increase in the hardness and compressive fracture strength. After oxidation at 800 ℃ for 40 h， porous oxide films were formed on the surface of four kinds of WMoNbCrTi high entropy alloys， and the oxide films fall off easily from substrate. The increase in Cr content has only slightly improves on the oxidation resistance at 800 ℃. The results provide essential experimental data and theoretical guidance for the development of refractory high entropy alloys.