improvement of Strength and Ductility of Ni_3Al and Challenge to a High Temperature Structural Material

由于Ni_3Al‘的屈服强度太低，不能用作高温结构材料，人们试图改善其力学性能。固溶强化是最基本、最重要的强化方法之一。许多元素固溶于Ni_3Al中，但Ni_3Al+M化合物是否通过B微合金化是不确定的，尤其是偏向富Ni侧是否是这些合金延展化所必需的。本文通过弯曲试验和拉伸试验研究了B和替代元素M同时合金化对Ni3Al延伸率的影响。Ni_3Al系通过添加Zr、Hf、V、Nb、Mo、W、Co、Pd、Cu、Cr、Mn和Fe等元素进行微合金化。Ni_3(Al，M)化合物，其中M完全取代Al原子，通过与富Ni侧的B微合金化来实现延性。相反，(Ni，M)_3Al化合物和(Ni，Mn)_3(Al，Mn)化合物是通过富Ni和富Al侧的B微合金化而实现延性的。在Ni_3Al+B合金中，除Fe和Ga外，M的合金化提高了合金的屈服强度。Pd、Ga、Si、Hf合金化提高了Ni3Al+B的断裂强度，而与其他元素合金化则降低了断裂强度。Ni_3Al+B合金的延伸率随Ga、Fe、Pd的合金化而增加，而与其他元素的合金化则降低。Hf和Pd分别是提高Ni3Al+B屈服强度和断裂强度的有效元素。合金化提高了Ni3Al+B的屈服强度和断裂强度，但降低了延伸率。另一方面，Pd的合金化提高了所有的力学性能，即屈服强度、断裂强度和延伸率。Ti、V、Co的合金化使Ni3Al+B的力学性能下降。讨论了添加M元素使Ni3Al+B塑性降低的原因。

Attempts have been made to improve the mechanical properties of Ni_3Al' because its yield strength is too low for using as a high temperature structural material. Solid solution hardening is one of the most fundamental and important strengthening methods. Many elements dissolve into Ni_3Al, but it is still uncertain whether Ni_3Al+M compounds are ductilized by microalloying with B.Particularly, it is interesting whether the deviation to the Ni-rich side is essential for ductilization of these alloys. In the present work, the effect of simultaneous alloying of B and the substitutional element M on ductilization of Ni_3Al has been investigated by the bend test and the tensile test. Ni_3Al is ductilized by macroalloying with Zr, Hf, V,NB,Mo, W,Co, Pd, Cu, Cr, Mn and Fe. The Ni_3 (Al, M) compounds, where M substitutes exclusively for the Al atoms, are ductilized by microalloying with B on the Ni-rich side. On the contrary, the (Ni, M)_3Al compounds and the (Ni, Mn)_3 (Al, Mn) compounds are ductilized by microalloying with B on both the Ni-rich and Al-rich sides. The yield strength of Ni_3Al+B increases by alloying with M except for Fe and Ga. The fracture strength of Ni_3Al+B increases by alloying with Pd, Ga, Si and Hf, but decreases with the other elements. Elongation of Ni_3Al+B increases by alloying with Ga, Fe and Pd, but decreases with other elements. Hf and Pd is the effective element for the increase of the yield strength and the fracture strength of Ni_3Al+B,respectively. Alloying with Hf leads to the increases of the yield strength and the fracture strength of Ni_3Al+B,but to the lowering of elongation. On the other hand, alloying with Pd improves all mechanical properties, i. e. the yield strength, the fracture strength and elongation. Alloying with Ti, V and Co leads to the lowering of mechanical properties of Ni_3Al+B.The reason why ductility of Ni_3Al+B is reduced by alloying with some elements M was discussed.