An ultrahigh strength steel with ultrafine-grained microstructure produced through superplastic forming

A novel procedure combined with superplastic forming was applied to produce an ultrahigh strength steel with ultrafine-grained microstructure. Although the hardness reached HRC65 at room temperature, the value of m = 0.38 and flow stress of 57 MPa were found during superplastic forming at 1023 K and strain rate of 10−4 s−1. Due to reasonable composition design, ultrahigh strength was ensured within a wide range of cooling rate after superplastic forming without the need of supplementary heat treatment.