Investigation into microstructure and mechanical properties of NiAl-Mo composites produced by directional solidification
Investigation into microstructure and mechanical properties of NiAl-Mo composites produced by directional solidification
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DOI：
10.1016/j.msea.2012.01.083
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发表时间：
2012-03-30
期刊：
影响因子：
6.4
通讯作者：
Buehrig-Polaczek, A.
中科院分区：
文献类型：
--
作者：
Hu, L.;Hu, W.;Buehrig-Polaczek, A.
标称成分为 Ni-43.8Al-9.5Mo (at.%) 的钼纤维增强 NiAl 原位复合材料是使用配备液态金属冷却 (LMC) 装置的实验室规模布里奇曼炉通过特殊控制的定向凝固生产的。通过电子显微镜（SEM、TEM、HRTEM）和微分析（EDX、SAED）对所生产的复合材料的微观结构进行了表征。通过拉伸试验检查高温（700℃、1100℃）下的强度和塑性。通过四点弯曲试验测量室温（RT）的断裂韧性。对于恒定的温度梯度（8.9 K/mm），发现单晶Mo纤维的排列和尺寸/间距主要由凝固速率控制。当凝固速率从 1.33 mm/min 降低到 0.33 mm/min 时，Mo 纤维逐渐从最初的不规则分布排列到平行于凝固方向的排列。高温下的强度和室温下的断裂韧性由 Mo 纤维排列决定：复合材料的屈服强度从随机 Mo 纤维排列的 700 ℃ 273 MPa 和 1100 ℃ 68 MPa 增加到 110 ℃ 811 MPa。 700 摄氏度，1100 摄氏度时为 344 兆帕，以获得排列良好的钼纤维。 Mo纤维排列后，RI断裂韧性也从8.7 MPa m(0.5)明显提高到14.5 MPa m(0.5)。Mo纤维排列对所生产的NiAl-Mo复合材料力学性能的影响将在主动强化和增韧机制方面进行讨论。 (C) 2012 Elsevier B.V. 保留所有权利。
Mo fiber reinforced NiAl in situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. The microstructure of as-produced composites was characterized by electron microscopy (SEM, TEM, HRTEM) and microanalysis (EDX, SAED). The strength and plasticity at elevated temperatures (700 degrees C, 1100 degrees C) were examined by tensile tests. The fracture toughness at room temperature (RT) was measured by four-point bending tests.For a constant temperature gradient (8.9 K/mm) it was found that the alignment and size/spacing of single crystalline Mo fibers were mainly controlled by the solidification rate. When the solidification rate decreased from 1.33 mm/min to 0.33 mm/min the Mo fibers arranged themselves gradually from an initially irregular distribution to an alignment parallel to the solidification direction.The strength at elevated temperatures and the fracture toughness at RT were dominated by the Mo fiber alignment: the yield strength of the composites increased from 273 MPa at 700 degrees C and 68 MPa at 1100 degrees C for a random Mo fiber arrangement to 811 MPa at 700 degrees C and 344 MPa at 1100 degrees C for well aligned Mo fibers. The fracture toughness at RI was also apparently improved from 8.7 MPa m(0.5) to 14.5 MPa m(0.5) upon Mo fiber alignment.The influence of Mo fiber alignment on the mechanical properties of as-produced NiAl-Mo composites will be discussed in terms of the active strengthening and toughening mechanisms. (C) 2012 Elsevier B.V. All rights reserved.