Structural aspect of chemical reaction between components of mechanically alloyed Al-MoO2 and Al-MoO3 composites

Abstract Mechanical alloying of aluminum powder with additions of 5 wt% MoO 2 and MoO 3 powders was used for producing Al-MoO 2 and Al-MoO 3 composites. Mechanical consolidation of as-milled composite powders was performed by means of preliminary pressing followed by the KOBO extrusion at 573 K and λ = 44 cross-section reduction ratio. Dilatometry and differential scanning calorimetry tests at the temperature range of 293–973 K were performed to study the chemical reactions between composite components in the solid/liquid state. Structural observations revealed the presence of Al 12 Mo intermetallic grains that result from a combined chemical reaction between the matrix and reinforcements. The phase transformation was studied using X-ray diffractometry as well as transmission and scanning electron microscopy methods. Structural observations performed for as-extruded composites revealed similar microstructures for Al-MoO 2 and Al-MoO 3 composites. Residual, coarse aluminum powder grains were surrounded with a mixture of nano-sized structural components containing heavily refined molybdenum and aluminum oxides uniformly distributed within nano-grained aluminum matrix. Some unrefined molybdenum oxide particles were also locally observed. It was concluded that the utilized alloying time, 34 h, was not long enough to complete the milling procedure.