Microstructure and reaction properties of Ni/Al micro-nano composites produced by accumulative roll bonding process

Abstract

Ni/Al micro-nano composites have received much attention due to their attractive properties, especially high energy density and stable strength. This presented work aims to propose a simple and cost-effective method for preparing Ni/Al micro-nano composites that have good reaction performance and specific tensile strength and explore their microstructure evolution and reaction property. The Ni/Al micro-nano composites were fabricated by the accumulative roll bonding (ARB) using pure nickel and Al foils. As the ARB cycles gradually increased, the foils get thinner and transition from a straight to a wavy shape, such as necking and fracture of Ni. The interface contact area was increased by the more uniform and slender nickel-aluminum layer distribution during ARB process. Furthermore, the energy density during the exothermic reactions of the Ni/Al composites firstly increased and then decreased with the decrease of interlayer thickness. The energy density of the Ni/Al micro-nano composite after 13th ARB cycles was 1362.5 J g−1, which was about 92% of the theoretical value. The initial reaction temperature of the composites decreased with the increase of rolling cycles. Al3Ni, Al3Ni2 and AlNi intermetallic phases were generated in exothermic reactions. Besides, the activation energies of Ni/Al composites calculated by Kissinger and Ozawa method were 52.91 and 59.68 kJ mol−1, respectively. After the 13th rolling cycle, the tensile strength was 368.70 MPa while the elongation was 4.2%.