Magnetic susceptibility and Mossbauer spectroscopy studies were carried out on the alloy series FeAl_1-xCu_x (0<x<or=0.4). The variation of susceptibility with temperature showed transitions from a paramagnetic to a spin glass phase for copper contents 0.15<or=x<or=0.25. For x=0.325 transitions from a paramagnetic to a ferromagnetic and from a ferromagnetic to a magnetic glass phase were observed as the temperature was decreased. Mossbauer spectra gave information on the microscopic conditions at the iron sites. The electron density at the iron nuclei increased linearly with copper concentration x. Distributions of hyperfine fields were observed for all alloys at 4.2 K and related to iron cluster structure. Comparison between phase transition temperatures obtained by susceptibility and Mossbauer observations gave information on the relaxation of clusters. The size of these clusters as a function of x was studied via a simulation calculation and used to account for the occurrence of a ferromagnetic phase at a critical value of x.