Abstract NiAl alloy is an important lightweight and heatproof structural material used for the service temperature up to 1000 °C. However, there are huge challenges in fabricating NiAl alloy sheets and forming thin-walled components. In order to solve this problem, a novel process of integrated forming and reaction synthesis using laminated Ni/Al foils as the initial blank was developed for fabricating NiAl alloy curved shells. The laminated Ni/Al foils were first formed into a curved shell at room temperature, then the shell was in-situ heat-treated under a proper pressure until the pure Ni and Al were transformed into intermetallic NiAl by reaction synthesis. The microstructure, defects such as voids and mechanical properties of the shell were investigated in order to evaluate the feasibility of the integrated process. The influence of loading pressure for fabricating the shell on the void size was studied quantitatively. A theoretical model was proposed to predict the thickness distribution of the shell. It was shown that the shell can be successfully fabricated by the forming and reaction synthesis integrated process. Thinning occurred in the whole region of the shell with the minimum and maximum thickness strain locating at ±80° and 0°, respectively. The voids in the shell mainly exist in the original Al foil regions and original Ni foil regions. The voids in the central region of the NiAl3 diffusion layers were inherited to the central region of fine-grained layers. The diffusion of Ni layers at high temperatures led to the appearance of linearly distributed voids in the central region of coarse-grained layers. Loading pressure facilitated microplastic deformation, leading to a maximum contact area between the mating surfaces, which further promoted the interdiffusion. Increasing the pressure enhanced the voids shrinkage while decreasing the size of voids. The difference in the displacement increment of each region prevented the edge region of the shell from achieving full densification, resulting in the uneven distribution of density and mechanical properties.

中文翻译：

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NiAl合金曲壳一体成型反应合成新工艺

摘要 NiAl合金是一种重要的轻质耐热结构材料，使用温度高达1000℃。然而，在制造 NiAl 合金板材和形成薄壁部件方面存在巨大挑战。为了解决这个问题，开发了一种以层压Ni/Al箔为初始坯料的一体成型和反应合成新工艺，用于制造NiAl合金弯曲壳。叠层Ni/Al箔首先在室温下形成弯曲的壳，然后在适当的压力下对壳进行原位热处理，直到纯Ni和Al通过反应合成转化为金属间NiAl。研究了壳的微观结构、缺陷等缺陷和力学性能，以评估集成工艺的可行性。定量研究了制造壳体的加载压力对空隙尺寸的影响。提出了一种预测壳体厚度分布的理论模型。结果表明，通过成型和反应合成一体化工艺可以成功制备外壳。减薄发生在壳的整个区域，最小和最大厚度应变分别位于±80°和0°。壳中的空隙主要存在于原始Al箔区域和原始Ni箔区域。NiAl3 扩散层中心区域的空隙被继承到细晶粒层的中心区域。Ni层在高温下的扩散导致在粗晶层的中心区域出现线性分布的空隙。加载压力促进微塑性变形，导致配合表面之间的接触面积最大，这进一步促进了相互扩散。增加压力会增强空隙收缩，同时减小空隙的尺寸。各区域位移增量的差异阻碍了壳体边缘区域实现完全致密化，导致密度和力学性能分布不均。