The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.
分别采用微结构分析[X 射线衍射、能量色散光谱、光发射光谱、原子力显微镜 (AFM) 和光学显微镜 (OM)]和力学(压痕和压缩)测试,研究了用机械化学方法加热等静压合成的 x = ∼ 19-21 wt% 的块状纳米晶 γ-Ni-x-Fe(n-Ni-Fe)的微结构和力学行为。结果表明,n-Ni-Fe(d ∼ 33 nm)的屈服强度(σ0.2)约为传统材料的 13 倍。在所研究的晶粒尺寸范围(33-100 nm)内,屈服强度随晶粒尺寸的变化与霍尔-佩奇关系基本一致。光学显微镜观察表明存在两组宏观带状变形痕迹,其方向大多与压缩轴成 45-55° 角,而原子力显微镜观察则发现这些带状痕迹由超细线组成。根据 n-Ni-Fe 的微观结构和变形形态特征,讨论了高强度的原因和可能的变形机制。