一种第四代单晶高温合金不同温度的拉伸性能各向异性

Tensile anisotropy of the fourth generation single crystal superalloy at different temperatures

采用籽晶法在定向凝固炉中制备了一种[001],[011]和[111]取向的第四代单晶高温合金,分别在 23 ℃,800 ℃和 980 ℃研究了合金不同取向的拉伸性能,利用光学显微镜、扫描电镜研究不同取向、不同温度的合金组织、断口形貌和断裂组织。结果表明:不同取向合金在垂直于晶体生长方向的截面上具有明显不同的铸态枝晶和热处理组织形貌。不同温度合金的屈服强度和抗拉强度按[111]、[001]、[011]取向的顺序降低。合金的伸长率与断面收缩率在 23℃和 980 ℃时[011]取向最大,而 800 ℃时[111]取向最大。23 ℃和 800 ℃不同取向合金拉伸为类解理断裂,980 ℃[001]、[111]合金拉伸为韧窝断裂,而[011]取向合金拉伸为类解理和韧窝混合断裂。拉伸断裂后,23 ℃和 800 ℃时不同取向合金的γ′相仍为立方体形状,980 ℃时[001]取向合金γ′相沿应力方向变长,[111]取向合金的γ′相变成平行四边形,而[011]取向合金的γ′相被单一密集滑移带剪切。

The fourth generation single crystal superalloy with [001],[011] and [111] orientations was cast using seed method in the directionally solidified furnace. The tensile properties of the alloy with different orientations were investigated at 23 ℃, 800 ℃ and 980 ℃.The alloy microstructure, fracture surface and fracture microstructure with different orientations at different temperatures were investigated by OM and SEM. The results show that the alloy with different orientations has obviously various as-cast dendritic structure and heat treated microstructure on the section perpendicular to the crystal growth direction. The yield strength and ultimate tensile strength of the alloy at different temperatures are decreased with the sequence of [111],[001] and [011] orientation. The elongation and contraction of area of the alloy with [011] orientation are the largest at 23 ℃ and 980 ℃, and those alloys with [111] orientation are the largest at 800 ℃. The tensile fractures of the alloy with different orientations at 23 ℃ and 800 ℃ are quasi- cleavage, while that the alloys with [111] and [001] orientations are dimple fractured, and that the alloy with [011] orientation shows quasi-cleavage and dimple mixture mode. After tensile fracture, the γ′ phase of alloy with different orientations at 23 ℃ and 800 ℃ still remains in cube shape. The γ′ phase of alloy with [001] orientation at 980 ℃ becomes longer along the stress direction, while that the alloy with [111] orientation turns parallelogram and that with [011] orientation is cut through by single slip band.