Inelastic neutron scattering spectra from C-15 phase superconducting alloys V2Hf, V2Ta, V2Hf0.8 Ta0.2, V2Zr0.5 Hf0.5 and V2Zr0.5 Hf0.33 Ta0.17 were measured by the neutron time-of-flight method, and their relative phonon densities of states were evaluated. The present results show that the phonon frequencies soften with the increase of the superconducting transition temperature Tc and harden with the decrease of the Tc, which is in agreement with our previous results of "The effect of Nb on phonons of superconductors C-15 V2Zr and V2(Zr0.5 Hf0.5)". This means that for these superconductors the elastic softening plays a role in enhancing Tc to some extent. It seems that between V2Zr or V2Hf and V2(Zr0.5 Hf0.5) there exists essential difference, which makes Tc increasing and the phonon frequencies softening for the formers while Tc decreasing and the phonon frequencies slightly hardening for the later after adding small amounts of Nb or Ta. It can be considered as the result of hybridzation of conduction bands, which is studied by means of the LMTO (linear combination of muffin-tin orbitals)method.