[en] We analyse the deformation mechanism in neutron-rich Cr, Fe and Ti isotopes with N=32-44 using a Skyrme-Hartree-Fock-Bogoliubov mean-field code employing a two-dimensional mesh representation in the cylindrical coordinate system. Evaluating the quadrupole deformation energy systematically, we show that the Skyrme parameter set SkM^* gives a quadrupole instability around the neutron numbers N - 38-42 in Cr isotopes, where the deformation energy curve suggests a transitional behavior with a shallow minimum extending to a large prolate deformation. The roles of a deformed N=38 gap and the position of the neutron g_9/2 orbit are analysed in detail. (author)