NbB_2 及び TaB_2 単結晶の高温硬度  [in Japanese] High Temperature Hardness of NbB_2 and TaB_2 Single Crystals  [in Japanese]

NbB2及びTaB2単結晶の (0001) 及び {1010} 面の20°-1100℃におけるKnoop硬度を測定した. (0001) 面では圧子長軸方向が〈1120〉及び〈1010〉方向において, {1010} 面では [0001] 及び〈1210〉方向において測定した. 硬度は温度とともに単調に減少し, 全温度領域においてH〈1010〉(0001)>H〈1120〉(0001)及びH〈1220〉{1010}>H[0001]{1010}なる関係を示した. 同一温度では (0001) 面の硬度が {1010} 面のそれより高い値を示した. lnHとTの間にはよい直線関係がなり立ち, T=0.15Tm及び0.3Tm付近の温度において直線に段が観察された. 高温領域においては柱面滑りが優勢に起こっていることが認められた.

The Knoop hardness measurements of NbB2 and TaB2 single crystals were made in the temperature range 20°-1100°C. The long axis orientations of the indentations made were along the ‹1120› and ‹1010› directions on the (0001) plane and along the [0001] and ‹1210› directions on the {1010} plane. Hardness decreased monotonously through all the testing temperatures, maintaining the relationships of H‹1010›(0001)>H‹1120›(0001) and H‹1210›{1001}>H[0001]{1010}. The hardness values of the (0001) plane were higher than those of {1010} plane in the given temperature. ln(H) vs. T kept linear relationship having steps near 0.15 and 0.3Tm. Predominant prismatic slips were observed at higher temperatures.