Fabrication of tungsten particles reinforced aluminum matrix composites using multi-pass friction stir processing: Evaluation of microstructural, mechanical and electrical behavior

Microstructure of Multi-Pass Friction-Stir-Processed Al-Zn-Mg-Cu Alloys Reinforced by Nano-Sized TiB2 Particles and the Effect of T6 Heat Treatment

“…With the increase in the processing passes, no particle-rich or -lean zone is observed and a more uniform TiB 2 distribution is obtained, as indicated in Figure 4b,c. This observation is consistent with the results of Huang et al [6] and Zhang et al [36], namely that multi-pass FSP improves the distribution of second-phase particles in an aluminum matrix due to the accumulated plastic strain. In addition, some TiB 2 particles are broken into several fragments as indicated by arrows in Figure 4a.…”

“…With the increase in the processing passes, no particle-rich or -lean zone is observed and a more uniform TiB2 distribution is obtained, as indicated in Figure 4b,c. This observation is consistent with the results of Huang et al [6] and Zhang Figure 4 shows the SEM images of the nugget zone in the FSP-treated PR alloys processed with different passes. It can be clearly seen that TiB 2 particles disperse in the matrix without any particle cluster in all the FSP-treated samples.…”

“…Since a more uniform particle distribution is introduced by multi-pass FSP, more interfaces between the particles and matrix are produced. During FSP, more dislocations are inclined to be produced from such interfaces [6]. The high dislocation density in the matrix induces the occurrence of pipe diffusion [41] and leads to the acceleration of the precipitating kinetic [15].…”

“…Especially by reducing the reinforcement particle size to the nanometer range, it has been reported that the tensile ductility of such PR alloys can be maintained or even enhanced with a simultaneous increase in tensile strength, depending on the processing process [3][4][5]. However, casting (i.e., liquid-state solidification) generally weakens ductility and toughness due to defects like porosity, particle-matrix debonding, and especially particle clustering [6]. Even the most vigorous stirring techniques like ultrasonic dispersion during casting are unable to break the agglomerates in the melt [7], which are pushed by the solidification front and ultimately cluster along the grain boundaries in the following solidification [8,9].…”

“…FSP, as a severe plastic deformation technique (SPD), has been proved to be one of the most efficient ways for microstructural modification in the solid-state [12]. It can effectively solve the above-mentioned problems of cast defects and particle clusters in PR alloys [6,13]. In addition, FSP is regarded as a promising grain refinement technique [14][15][16][17].…”