The microstructure and mechanical properties of reaction synthesized Ni-Al intermetallic sheets by pure Ni/Al foils with different thickness ratios

The Ni-Al intermetallic sheets were prepared by the reaction synthesis of pure Ni and Al foils with different thickness ratios. The first stage was performed at 640 degrees C/20 MPa/6 h to consume Al layers, and the second stage was performed at 1200 degrees C/20 MPa/1 h to complete the synthesis of Ni-Al intermetallic sheets. The thickness ratios of original Ni and Al foils strongly affected the microstructure and mechanical properties of NiAl intermetallic sheets. When Ni/Al thickness ratio was 1:1.5 (R1:1.5), the microstructure was single-phase NiAl with bimodal grain structure, and it transformed into coarse grains dominated single-phase NiAl structure when Ni/Al thickness ratio was 1:1 (R1:1). The microstructures changed to NiAl+Ni3Al+Ni when the ratios were 1:0.63 (R1:0.63) and 1:0.25 (R1:0.25). At ambient temperature, Samples R1:0.25 and R1:0.63 had high strength, while Samples R1:1 and R1:1.5 showed serious brittleness. At high temperature, Sample R1:1 showed preferable ductility with the elongation of 61.3%, 71.4% and 101.3% at 800 degrees C, 900 degrees C and 1000 degrees C, respectively; Sample R1:0.63 showed the highest tensile strength, with the values of 350.3 MPa, 230.5 MPa and 140.2 MPa at 800 degrees C, 900 degrees C and 1000 degrees C, respectively. For the fracture at ambient temperature, Sample R1:0.25 showed a mixed fracture mode of dimple fracture and quasi-cleavage fracture; the fracture mode of Sample R1:0.63 was mainly cleavage fracture; Sample R1:1 showed a typical brittle cleavage fracture with a large number of riverlike patterns; the fracture mode of Sample R1:1.5 was brittle transgranular fracture for coarse grain layers (CGLs) and intergranular fracture for fine grain layers (FGLs). At high temperature, Samples R1:1.5 and R1:1 were mixed fracture modes of dimple fracture and quasi-cleavage fracture; the fracture mode of Sample R1:0.63 was mixed quasi-cleavage and cleavage fracture; the fracture mode of Sample R1:0.25 was single cleavage fracture with microcracks at the NiAl layers.

Automated summary

This study prepared Ni-Al intermetallic sheets by the reaction synthesis of pure Ni and Al foils with different thickness ratios, and found that the original thickness ratios of Ni and Al foils affected the microstructure and mechanical properties of the Ni-Al intermetallic sheets.