This work reports on the production of Ni-50 at% Ti powders by a planetary ball mill in various times（0.5, 1, 2, 6, 20, 36, 54 and 120 h） and subsequent heat treatment in Ar atmosphere at 820 °C. Study of powde...This work reports on the production of Ni-50 at% Ti powders by a planetary ball mill in various times（0.5, 1, 2, 6, 20, 36, 54 and 120 h） and subsequent heat treatment in Ar atmosphere at 820 °C. Study of powders structure after milling and heat treatment was carried out by scanning electron microscopy and X-ray diffractometry. According to the results, after milling for 6 hours NiTi phase formed, and by the milling evolution up to 54 h, it became the dominant phase. It was found that by the milling development, a layer structure in powder particles was formed, also by increasing the milling time a more homogeneous structure was obtained. Amorphous Ni Ti transformed into ordered Ni Ti, Ni_3Ti, NiTi_2 and minor TiO_2 and TiO after heat treatment at 820 °C for 1 h.展开更多
The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron dis- charge machining. Failure forms of the AlTiN-coated micro-grain carbide endmill when used for th...The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron dis- charge machining. Failure forms of the AlTiN-coated micro-grain carbide endmill when used for the machining of JIS SKD61 (HRC 53), a widely used material in die/mold manufacturing, are investigated. The endmill shows a characteristic that tool life decreases greatly due to the chipping when overload occurs or the rapid increase of wear when over-heat accumulation in cutting edges. As a consequence of the investigation, a strategy to regulate heat generation in the end milling process is proposed. This is accomplished by controlling the cutting arc length, i.e. the length of each flute engaging workpiece in a cutting cycle. Case studies on the slot end milling and comer rounding are conducted. The results show that the proposed strategy suggests the optimal tool path as well as the optimal pitch between successive tool paths under the cutting time criterion.展开更多
基金support of this research by central office of ACECR(Academic Center for Education,Culture and Research)
文摘This work reports on the production of Ni-50 at% Ti powders by a planetary ball mill in various times（0.5, 1, 2, 6, 20, 36, 54 and 120 h） and subsequent heat treatment in Ar atmosphere at 820 °C. Study of powders structure after milling and heat treatment was carried out by scanning electron microscopy and X-ray diffractometry. According to the results, after milling for 6 hours NiTi phase formed, and by the milling evolution up to 54 h, it became the dominant phase. It was found that by the milling development, a layer structure in powder particles was formed, also by increasing the milling time a more homogeneous structure was obtained. Amorphous Ni Ti transformed into ordered Ni Ti, Ni_3Ti, NiTi_2 and minor TiO_2 and TiO after heat treatment at 820 °C for 1 h.
文摘The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron dis- charge machining. Failure forms of the AlTiN-coated micro-grain carbide endmill when used for the machining of JIS SKD61 (HRC 53), a widely used material in die/mold manufacturing, are investigated. The endmill shows a characteristic that tool life decreases greatly due to the chipping when overload occurs or the rapid increase of wear when over-heat accumulation in cutting edges. As a consequence of the investigation, a strategy to regulate heat generation in the end milling process is proposed. This is accomplished by controlling the cutting arc length, i.e. the length of each flute engaging workpiece in a cutting cycle. Case studies on the slot end milling and comer rounding are conducted. The results show that the proposed strategy suggests the optimal tool path as well as the optimal pitch between successive tool paths under the cutting time criterion.
