Study of the similarities and differences in TEM and XRD characterization of several reactive milling systems

M.F. GIORDANA; M.R ESQUIVEL; E. ZELAYA

Bariloche

Congreso; XXIII Latin American Symposium on Solid State Physics; 2018

Universidad de Rio Negro-Comisión Nacional de Energía Atomica

The main objective of reactive milling is to achievean intermetallic compound as a product of two ormore alleys. Depending on the case involved, four differentstages can be identied during reactive milling:initial, intermediate, nal and completion. The initialstage is controlled by fracture process. During thisstep, compositional homogeneity is not reached. Theintermediate stage is controlled by both fracture andcold welding. At this stage, compositional changes areclearly evidenced. As milling continues, the cycle offracture and cold welding reaches equilibrium and theformation of new structures is identied at the nalstage. The completion stage occurs when further millingonly lead to a renement of the powder, as in asteady state processing stage [1; 2]. Alternatively, a decompositionof the major nal structure might occur.These four stages are generally identied taking intoaccount x-rays diraction (XRD) and scanning electronmicroscopy (SEM) results. The rst techniquegives a statistical analysis of the former alleys compositionchanges and the nal intermetallics formation,while SEM can evaluate the morphological and sizeevolution of particles through the four stages. Transmissionelectron microscopy (TEM) is a useful techniqueto complement both SEM and XRD results. Thecombination of several TEM techniques can provideinformation about the inner grain structure and partialalley segregation. Moreover, the higher accuracyof TEM techniques at nanoscale allows to identify theformation of intermetallics at shorter integrated millingtimes than XRD. The aim of this work is to showhow statistical techniques like XRD and SEM combinedwith TEM techniques can elucidate a completecharacterization of each milling stage. To achieve thisgoal a summary of dierent metal-based reacting systemsis discussed.[1] C. Suryanarayana, Progress in Materials Science, 46, 1(2001).[2] M.F. Giordana et. al., Metallography, Microstructureand Analysis, 6, 139 (2017).