Jianjun CUI
,
Musen LI
,
Longwei YIN
,
Guiyi WAN
,
Zhaoyin HAO
材料科学技术（英文）
In this paper, crystal growth instability of diamond was studied in a Fe-Ni-C system at high temperature-high pressure (HPHT). As any other crystal grown from solution, the flat or smooth growth interface of the diamond crystal is highly sensitive to growth conditions. The growth front interface should be of great importance to understand the diamond growth process. The presence of cellular growth interface by transmission electron microscopy indicated that there existed a narrow constitutional supercooling zone in front of the growth interface. Several parallel layers with cellular interface by TEM directly suggested that the diamond grows from the solution of carbon in the molten catalyst layer by layer, which is in accordance with the result obtained by scanning electron microscopy in this paper. Impurities are trapped by rapidly advancing growth layers during the diamond growth and they impose a great effect on the growth front stability. As the growth front interface approaches the impurity particle to a distance of about 10-5~10-7 cm, appreciable molecular forces begin to operate between them, and the impurity particle is trapped as the growth rate reaches a critical value. As a result, the driving force for crystallization under the impurity particles becomes smaller, the front buckles under the particle. An impurity naturally reduces the growth rate to a different extent.
关键词:
HPHT diamond growth
,
null
,
null
,
null
李雪飞
,
黄利军
,
黄旭
,
储俊鹏
,
张明杰
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2015.06.016
采用VAR三次熔炼方法制备含有YG8刀具硬质合金杂质的铸锭,铸锭经开坯改锻制成φ40 mm棒材,超声波探伤确定杂质位置.用光学显微镜和扫描电镜对杂质边缘的组织形貌及成分进行分析.研究结果表明,硬质合金部分熔化,边界含有明显的过渡区域,过渡区含有钛合金基体元素和刀具硬质合金元素并发生了扩散.杂质的存在会引起应力集中,容易萌生疲劳裂纹,进而影响产品的使用性能.
关键词:
钛合金
,
硬质合金
,
杂质
