Can we call human evolution as adaptive radiation?

No, we cannot call human evolution as adaptive radiation.

Adaptive radiation is the diversifying of organisms from a single species due to various factors such as competition for resources, isolation in a different environment, etc.

Human evolution was a gradual process of anatomical, physiological and changes that took place over a long period of time. The humans did not diversify into many species from a common ancestor. They rather enhanced over the period of time, suiting best according to their current environment.