Ultra-strong nickel aluminum bronze alloys with ultrafine microstructures by continuous heavy hot rolling

Abstract

In this work, nickel aluminum bronze (NAB) alloys with superior mechanical properties were prepared by continuous heavy hot rolling at two different temperatures. When rolled at 950 °C with a reduction ratio of 90%, slabs with an ultrahigh strength over 1300 MPa and an elongation nearly 5% can be obtained, and the strength can be further improved by subsequent ageing process. The contribution of each strengthening factor to the yield stress was analysed using a semiquantitative model. The results show that grain refinement and dislocation strengthening are the two most important factors. Besides, a subsequent 700 °C/5min heat treatment was carried out to improve the ductility of rolled slabs to nearly 15%, while the yield strength can be maintained at around 800 MPa. After heat treatment at 700 °C, high density annealling twins were generated. It was revealed that the intracrystalline twin boundaries helped to refine the microstructures and such refinement benefited the strength and ductility in many ways.