Abstract Due to the intrinsic brittleness of NiAl alloy, its sheets are difficult to fabricate with traditional casting and rolling methods. To solve this problem, a novel NiAl alloy sheet with a special bimodal laminated structure was successfully designed and fabricated via the in-situ solid-state reaction synthesis using pure Ni and Al foils. The mechanical properties of the bimodal laminated NiAl alloy sheet were tested by hot tensile tests at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.01/s to 0.0005/s. To clarify the deformation mechanism, the deformation microstructure was characterized by scanning electron microscopy and electron backscatter diffraction technology. The fracture behavior was characterized by a three dimensional X-ray microscope. It was found that the sheet with the bimodal laminated structure composed of overlapped coarse-grained layers (CGLs) and fine-grained layers (FGLs) exhibits a significant deformation incompatibility between CGLs and FGLs, leading to a special deformation and fracture behavior. During hot deformation, dislocations mainly accommodate in FGLs at the beginning, and the coarse grains then begin to play a major role in replacing the privilege of FGLs and vital in storing dislocations during further deformation. The bimodal laminated grains are broken up into many fragments and the average grain sizes are refined after deformation due to the transformation of low angle boundaries into high angle boundaries. The nucleation of dynamic recrystallization grains preferentially takes place in FGLs, and DRX will occur in CGLs when sufficient strain and storage energy are accumulated. The fracture surface demonstrates a jagged fracture pattern parallel to the loading direction, which results from the special laminated grain structure. The fracture morphology along the thickness direction experiences dramatic changes related to the non-uniform strain distribution, which presented as the density and size distribution of voids in 3D space. The study is vital to guiding the high temperature forming and service performance of NiAl alloy.

中文翻译：

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原位反应合成新型双峰层状结构NiAl合金薄板的变形和断裂行为

摘要 由于NiAl合金固有的脆性，其板材难以用传统的铸轧方法制造。为了解决这个问题，通过使用纯Ni和Al箔的原位固态反应合成，成功设计并制造了一种具有特殊双​​峰层压结构的新型NiAl合金板。通过在 850°C 至 1000°C 的温度范围和 0.01/s 至 0.0005/s 的应变速率下进行热拉伸试验，测试了双峰叠层 NiAl 合金板的机械性能。为阐明变形机制，采用扫描电子显微镜和电子背散射衍射技术对变形微观结构进行表征。断裂行为由三维 X 射线显微镜表征。结果表明，由重叠的粗晶层（CGLs）和细晶层（FGLs）组成的双峰层压结构的板材在CGLs和FGLs之间表现出显着的变形不相容性，导致特殊的变形和断裂行为。在热变形过程中，位错最初主要容纳在 FGLs 中，然后粗晶粒开始在取代 FGLs 特权方面发挥重要作用，并在进一步变形过程中对存储位错至关重要。由于低角度晶界向高角度晶界的转变，双峰层状晶粒破碎成许多碎片，变形后平均晶粒尺寸细化。动态再结晶晶粒的成核优先发生在 FGLs 中，当积累足够的应变和存储能量时，CGL 中会发生 DRX。断裂面呈现平行于加载方向的锯齿状断裂模式，这是由特殊的层状晶粒结构造成的。沿厚度方向的断裂形态经历了与非均匀应变分布相关的剧烈变化，表现为 3D 空间中空隙的密度和尺寸分布。该研究对于指导NiAl合金的高温成形和使用性能至关重要。它表现为 3D 空间中空隙的密度和尺寸分布。该研究对于指导NiAl合金的高温成形和使用性能至关重要。它表现为 3D 空间中空隙的密度和尺寸分布。该研究对于指导NiAl合金的高温成形和使用性能至关重要。