Z.Y.Chen
,
L.J.Xu
,
F.T.Kong
,
Q.Shu
,
Y.Y.Chen
金属学报(英文版)
The mathematics model for temperature field of water-cooling copper crucible induction skull melting process was established. The program for simulating temperature field of melting process was developed with finite element method. The temperature field of the melting process for Ti-47Al-2Cr-2Nb aUoy was calculated. During melting period, the temperature is raised gradually along radius augmentation direction. The elements of the charge near the crucible wall are molten first. The center elements of the charge are molten last. The melting time of the center element is just that of all the charge melting. The melting time of Ti-47Al-2Cr-2Nb alloy is 15min. In which, the charge was heated by low power 80kW for 9min and by high power 300kW for 6min. When melting Ti-47AI-2Cr-2Nb aUoy,the loading power is nearly direct proportion to melt temperature. Increasing loading power may raise melt temperature. The best melting power of Ti-47Al-2Cr-2Nb alloy is 305-310kW. This is identical with the melting test and has guidance sense to the melting process of actual titanium alloy.
关键词:
TiAl base alloy
,
null
,
null
胡锐
,
柳翊
,
张铁邦
,
寇宏超
,
李金山
金属学报
doi:10.3724/SP.J.1037.2013.00441
通过研究TiAl合金中不同Al含量和不同β相稳定元素含量的变化,分析了Al含量和β相稳定元素对TiAl合金初生相选择与凝固特征的影响.结果表明,单一β相凝固的TiAl基合金含Al量低,结晶温度范围窄,凝固组织均匀细化.采用背散射法(BSE)观察并分析了不同过冷度下铸造TiAl基合金非平衡凝固的枝晶形貌,运用经典竞争形核理论研究了Ti48Al2Cr2Nb(原子分数,％)包晶合金非平衡凝固中β相与α相的形核与过冷度的关系,并计算了Ti48Al2Cr2Nb合金深过冷凝固中的β相(bcc)和α相(hcp)的临界形核功及稳态形核率,结果表明,在约15K/s的冷速下,Ti48Al2Cr2Nb合金在所能达到的过冷度(≤370 K)范围内凝固时,β相始终为领先相优先形核.以过包晶凝固的TiAl基合金,其Al含量高,结晶温度范围窄,凝固枝晶细小,趋向逐层凝固,可减少并消除糊状凝固所造成的疏松和热裂趋势.β相稳定元素对凝固路径的影响取决于其Al当量,并可使TiAl合金的凝固路径从过包晶凝固转变为亚包晶凝固；过多的Al含量将导致铸造TiAl合金凝固组织中存在过多γ相,从而影响合金的强度和塑性.
关键词:
TiAl基合金
,
非平衡凝固
,
相选择
,
过冷
,
初生相
吴士平
,
郭景杰
,
贾均
金属学报
以N--S方程、连续性方程及Fourier导热方程为基础,结合离心力、重力及Coriolis力, 在实验的基础上建立了立式离心铸造充型过程及凝固过程数学模型. 并且依据此模型对TiAl基合金排气阀立式离心铸造过程温度场、流场及压力场进行了数值模拟. 数值模拟结果表明, 离心铸造的充型过程存在正向和反向两个充填过程, 在入口处易出现卷气缺陷. 凝固过程也存在正向和反向两个凝固顺序, 在靠近先充填一侧易于形成偏轴线缩松缺陷.
关键词:
TiAl基合金
,
centrifugal casting
,
null
