定向凝固NiAl-Mo过共晶合金组织演变及性能

Microstructure evolution and mechanical properties of a directionally solidified NiAl-Mo hyper-eutectic alloy

摘要:

采用液态金属高温度梯度定向凝固装置制备了NiAl-16Mo(at.%)过共晶合金,研究了生长速率对合金组织演变及性能的影响。在生长速率为12~300μm/s范围内,该合金的凝固组织为初生Mo枝晶与NiAl/Mo纤维共晶的混合组织。随生长速率增加,初生Mo枝晶的体积分数由12μm/s的7.21%增加到 300μm/s的11.42%,Mo枝晶尺度和间距同时随之减小。性能测试结果表明,室温断裂韧性和高温强度随生长速率增加而降低,同时对合金强韧化机理进行了探讨。

Abstract:

A hyper-eutectic alloy, with nominal composition Ni-42Al-16Mo (at. %), was directionally solidified at growth rates ranging from 12~300μm/s by Liquid Metal Cooling (LMC) technique. Microstructural examination reveals that the NiAl-16Mo alloy was composed of primary Mo dendrite and NiAl/Mo eutectic cell in all the growth conditions employed. With the growth rates increasing from 12μm/s to 300μm/s, the volume fraction of Mo primary dendrite increased from 7.21% to 11.42%, while the size and the arm spacing of Mo primary dendrite reduces simultaneously. The corresponding room temperature fracture toughness (RTFT) and ultimate high temperature compressive strength (UTCS) decrease with increasing of growth rates, the toughening and strengthening mechanism of composite was also discussed.