Precipitation in nanostructured alloys: A brief review

Precipitates have been utilized to strengthen various alloys since early last century. Nanostructured (NS) or ultrafine grain (UFG) structured alloys were extensively developed in recent decades, facing a common challenge of limited ductility. While introducing precipitates emerged as an effective strategy to solve the strength-ductility tradeoff issue, the precipitation behavior in NS or UFG alloys differs from that in conventional coarse-grained counterparts. This article provides a review on the scientific discovery of precipitation in NS or UFG alloys in the past 20 years, including the formation mechanism and growth of precipitates, the interplay between precipitates and solid solutes, dislocations, or grain boundaries, as well as the consequent mechanical behavior. Specifically, this article covers Al alloys, Mg alloys, Ti alloys, and high-entropy alloys. Modern research trends in this field are highlighted.