Synthesis of Ultrafine Crystal/Nanocrystalline TiAl-based Alloy by in Situ Sintering

摘要:

研究了原位烧结法制备TiAl基超细晶/纳米晶合金。首先，通过球磨方式细化TiH2, Al, Si 和 Nb 粉，然后将球磨后粉末进行放电等离子烧结。利用X射线衍射仪、扫描电镜和透射电镜分析球磨粉末及其烧结块体的特性，利用差热分析仪测试高温抗氧化性。试验结果显示，球磨过程中产生了非晶、Ti3Al纳米晶和TiH2的分解产物，球磨后粉末经高温烧结时，这些细小粉末迅速地转变成TiAl和Ti3Al相，TiAl相的晶粒尺寸为500 nm~1 μm，Ti3Al相为几个纳米，这种超细烧结组织在1000 ℃下非常稳定，而且具有良好的抗氧化性

Abstract:

The preparation of TiAl-based alloys with ultrafine crystal/nanocrystalline by in situ sintering was investigated. TiH2, Al, Si and Nb powders were firstly refined to the nanoscale level by ball milling; then, the milled powders were pressed into green compacts, which were sintered into bulks by spark plasma sintering (SPS). The functional characteristics of milled powders and sintered bulk were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron?microscope (TEM). High temperature?oxidation resistance was examined by differential scanning calorimeter (DSC). The results reveal that amorphous products,?Ti3Al nanocrystalline?and decomposition?products of TiH2 are formed during milling. When milled powders are sintered at high temperature, these fine powders rapidly transform into TiAl and Ti3Al phase. The grain sizes of TiAl and Ti3Al are 500 nm~1 μm and a few nanometers, respectively. This sintered bulk ultrafine microstructure is?quite stable?below?1000 oC, and has excellent oxidation resistance