<p>Over the past few years, the Cu element has attracted much attention in duplex stainless steels. It undoubtedly holds advantageous in regulating the two-phase proportion and austenite stability and is also one of the crucial factors affecting the corrosion resistance. However, the systematic research on the impact of Cu addition to lean duplex stainless steels remains insufficient. In this study, a novel Cu-alloyed Mn-N-type 20Cr lean duplex stainless steel was developed and the effect of Cu on the strain hardening capacity and corrosion resistance was analyzed. The results show that the Cu addition increases the volume fraction and stability of the austenite, retards the martensitic transformation, and extends the transformation-induced plasticity effect to a wider strain range. Compared to the Cu-free steel, the plasticity of Cu-containing steel can be increased by ~ 26%. Additionally, the addition of Cu redistributes the Cr and N elements in the ferrite and austenite phases, thereby improving the corrosion resistance of the lean duplex stainless steel.</p>