First, the conclusion is that forging significantly improves the overall mechanical properties of 4140 steel.
The raw material, 4140 steel, can be further forged to eliminate defects such as porosity and inclusions, refine grains, and obtain a uniform forged microstructure.
However, forging alone has limited effect on improving the performance of 4140 steel. Therefore, it needs to be combined with heat treatment (quenching + high-temperature tempering) to fully maximize its performance.