[en] This paper examines the nucleation-and-growth processes that occur and the metastable states that are achieved at intermediate stages during moderate-temperature isothermal aging. The author considers the following with reference to binary and multicomonent Ti-TM alloys: the aging of the w+b-structure; the precipitation from b-Ti-TM alloys of a second, solutelean, bcc phase designated b' (the so-called ''phase separation'' reaction); the decomposition of b into a+b and practical methods of distinguishing between the a-phase and the aged w-phase precipitates; the effects of various ternary additions on the kinetics and products of the aging reaction. Consideration is given to b-phase decomposition into a pair of equilibrium bcc phases designated b' and b''. The purpose of considering this reaction is twofold: to draw attention to the distinction between the b to b'+b nonequilibrium phase= spearation reaction and the reaction b to b'+b'' where b/(b'+b'') represents an equilibrium solid-state miscibility gap; and because this b-phase imminscibility reaction once played a role in the development of the ternary Ti-Zr-Nb technical superconductors