The effect of cold deformation and annealing temperature on the microstructure evolution and mechanical properties isshown in this research together with a unique short strategy for manufacturing lean duplex stainless steel bars. Furthermore,the effects of post-weld heat treatment (PWHT) and cooling treatments on the microstructure and mechanical properties ofLDX 2101 bars are being investigated. The results demonstrate that the austenite produces a large number of deformationtwins and strain-induced martensite (SIM) as cold deformation increases, and the SIM and austenite follow the traditionalK–S and N–W orientation relationships. The best mechanical properties overall are achieved in LDX 2101 bars that havebeen annealed at 1020 °C. Moreover, short-time PWHT improves the austenite proportion in the heat-affected zone andweld metal, and PWHT can greatly enhance the overall mechanical properties of the welded joints. Additionally, the optimalheat treatment temperature of the welded joints is 1050–1080 ℃. Furthermore, compared to those treated with air cooling,the mechanical properties of the welded joints treated with water quenching following flash butt welding are superior. As aresult, it is recommended that following flash butt welding, the welded joints are given a water-quenching treatment.