Study of precipitates formed in a wrought aluminum alloy by means of atomic force microscopy

A study of the particles precipitated during heat treating a Type 6061 wrought aluminum alloy was carried out by means of atomic force microscopy and scanning electron microscopy (SEM). The specimens were cut from hot-extruded bars and were heat-treated to peak hardness and overaged stages to obtain precipitates of different sizes. The samples were prepared by standard metallographic techniques before being examined with either type of microscope. Observations with the atomic force microscope (AFM) were made in the topographic and lateral force modes, as each method yields different information. The former mode is issued to identify the particles and measure their size and shape, whereas the latter allows for data related to superficial characteristics. It is concluded that both types of microscopic examinations complement each other and that they can be used in conjunction to obtain a deeper understanding of precipitation behaviour and kinetics.