マイクロサイズ シケンヘン ニヨル TiAl キキンゾクカン カゴウブツ ノ

A micro-sized fracture toughness testing technique has been applied to investigate the fracture properties of colonies in a fully lamellar Ti-46Al-5Nb-1W alloy. Micro-sized cantilever specimens with a size≈10×20×50 μm3 were prepared by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 5 μm were also introduced into these specimens by focused ion beam machining. Fracture tests were successfully completed using a mechanical testing machine for micro-sized specimens at room temperature. The fracture toughness values obtained were in the range 1.4-6.9 MPam1/2. Fracture surface observations indicate that these variations are due to differences in local lamellar orientations ahead of the notch. These fracture toughness values are also lower than those having been previously reported in conventional samples. This may be due to the absence of significant extrinsic toughening mechanisms in these micro-sized specimens. Fracture mechanisms of these alloys are also considered on the micrometer scale. The results obtained in this investigation give important and fundamental information on the development of TiAl based alloys with high fracture toughness