<p>Unsteady-state upward transient solidification experiments were performed with Al-3.2Bi-0.5Cu/0.5Zn/0.5Nb (wt.%) alloys to evaluate the effect of solidification thermal parameters, such as growth and cooling rates (<i>V</i>_L and <i>T</i>_R), on the microstructure. A water-cooled solidification device coupled to a data acquisition system was used. The generated thermal data were used to determine the thermal parameters. Scanning electron microscopy techniques were applied to characterize the typical solidification microstructure of all investigated alloys, which consisted of Al_α + solid Bi globules + Fe intermetallic, where Al_α represented the Al-rich phases of each alloy. The Bi globules were observed dispersed in the Al_α matrices with different diameter sizes. The variation of Bi globules diameter (φ) with <i>V</i>_L and <i>T</i>_R was characterized by experimental growth laws represented by mathematical expressions given by φ = 3.3(<i>V</i>_L)^− 0.38 all the evaluated compositions, φ = 4.8(<i>T</i>_R)^− 0.2 for the Al-3.2Bi/0.5Zn/0.5Nb (wt.%) alloys and φ = 3.6(<i>T</i>_R)^− 0.12 for the Al-3.2Bi-0.5Cu (wt.%). It was observed that the Cu element played a fundamental role in the refinement of solid Bi globules, since lower φ values ​​were observed for Al-3.2Bi-0.5Cu (wt.%) alloy.</p>