镍基高温合金在变形热处理过程中的组织和织构演变

Microstructure and Texture Evolution of Ni-based Superalloy During Deformation and Thermomechanical Treatments

摘要:

采用电子背向散射衍射技术研究了镍基高温合金冷变形和再结晶退火过程中的组织演变、晶界特征分布、应变分布及织构演变规律。结果表明，当冷变形量较小（ε≤45%）时，晶粒沿着轧制方向被拉长，呈扁平状于基体中均匀分布，应力主要集中在晶界和孪晶界（TB）附近，大角度晶界（HAGBs）和TBs逐渐向亚晶界（Sub-GBs）和小角度晶界（LAGBs）转变。同时，出现Goss织构 {110}<001>、Brass-R织构{111}<112>、Twinned-Copper织构{552}<115>和Copper织构{112}<111>。当轧制压下量超过70%时，晶粒形状逐渐从扁平变为纤维状，晶粒的变形均匀性逐渐变好，应变分布变得均匀，LAGBs开始占主导地位。同时，织构类型保持不变，但织构强度增加。在1120 ℃退火15 min后，孪晶的长度分数随着轧制压下量的增加而增加。同时，变形织构转变为再结晶织构，织构类型增加，但织构强度减弱。此外，当退火孪晶的比例增加时，Copper织构{112}<111>不断向Twinned-Copper织构{552}<115>转变，并且经过30%~80%轧制变形的试样产生织构{124}<211>。

关键词:镍基高温合金;冷轧;退火孪晶;晶界特征分布;织构演变

Abstract:

The microstructure evolution, grain boundary character distribution, strain distribution, and texture evolution of Ni-based superalloy during cold rolling and subsequent recrystallization annealing treatments were studied by electron back-scattered diffraction technique. Results show that when the cold deformation degree is small (ε≤45%), the grains are elongated along the rolling direction into a flat shape and distributed evenly in the matrix. The strain is mainly concentrated near the grain boundary and the twin boundary (TB), and the high-angle grain boundaries (HAGBs) and TBs are gradually transformed into sub-grain boundaries (Sub-GBs) and low-angle grain boundaries (LAGBs). Meanwhile, the Goss texture {110}<001>, Brass-R texture {111}<112>, Twinned-Copper texture {552}<115>, and Copper texture {112}<111> appear. When the rolling reduction exceeds 70%, the grain shape gradually changes from flat to fibrous, the deformation uniformity of the grains gradually becomes better, the strain distribution becomes uniform, and LAGBs begin to dominate. In addition, the texture types do not change, but the texture intensity increases. After the annealing at 1120 °C for 15 min, the length fraction of annealing twins is increased with increasing the rolling reduction. Besides, the deformation textures are transformed into the recrystallization textures, the texture types are increased, but the texture intensity weakens. Furthermore, the Copper texture {112}<111> is continuously transformed into the Twinned-Copper texture {552}<115> when the proportion of annealing twins increases. Additionally, the {124}<211> texture is generated in the as-annealed alloy after rolling reduction of 30%–80%.

Key words:Ni-based superalloy;cold rolling;annealing twins;grain boundary character distribution;texture evolution