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在熔体温度为2323 K,抽拉速率为100μm/s的条件下对Nb-Ti-Si基超高温合金进行了有坩埚整体定向凝固(DS),然后对定向凝固试样进行了2种不同工艺的热处理:即1723 K/50 h高温均匀化处理(HT1)和1623 K/50 h+1723 K/50 h+1373 K/50 h复合热处理(HT2)。采用XRD,SEM和EDS等分析手段研究热处理对定向凝固合金微观组织及其力学性能的影响。结果表明,热处理后合金中大尺寸初生硅化物的体积分数下降,2种方式的热处理均能有效减轻甚至消除合金中的成分偏析。热处理后原DS试样中Nbss+(Nb,X)_5Si_3共晶胞的边界完全消失。相比HT1处理,HT2处理后试样中硅化物的分布更加均匀。与DS试样相比,经HT2处理后试样的室温断裂韧性值增加了12.3%(约19.2 MPa·m~(1/2)),且其抗拉伸强度增加了26.6%(最大值达到933.2 MPa)。力学性能的改善主要归因于热处理后组织中(Nb,X)_5Si_3颗粒弥散分布以及韧性Nbss相的形状、尺寸及含量均发生变化。
The whole crucible solidification (DS) was carried out on the Nb-Ti-Si based superalloy at a melt temperature of 2323 K and a pull rate of 100 μm / s, and then the directional solidification samples were subjected to two different Process heat treatment: 1723 K / 50 h high temperature homogenization (HT1) and 1623 K / 50 h + 1723 K / 50 h + 1373 K / 50 h composite heat treatment (HT2). The effects of heat treatment on the microstructure and mechanical properties of the directional solidification alloy were investigated by XRD, SEM and EDS. The results show that the volume fraction of large size primary silicide decreases after heat treatment, and the heat treatment of both methods can effectively reduce or even eliminate the component segregation in the alloy. The boundary of Nbss + (Nb, X) _5Si_3 eutectic cells disappeared completely in the original DS sample after heat treatment. Compared with HT1 treatment, the distribution of silicide in HT2 treated samples is more uniform. Compared with the DS sample, the room temperature fracture toughness of the sample after HT2 treatment increased by 12.3% (about 19.2 MPa · m ~ (1/2)), and its tensile strength increased by 26.6% (maximum reached 933.2 MPa). The improvement of mechanical properties is mainly attributed to the change of the shape, size and content of (Nb, X) _5Si_3 particles in the microstructure and tough Nb Nb phase after heat treatment.