| Due to their low density and good strength, aluminum alloys have a wide variety of industrial applications, but its further application is largely limited because of the poor wear resistance. In this paper,it is investigated and analyzed for the influence of the number of friction stir processing(FSP) pass, traversing speed, rotational speed, the hybrid particles weight, hybrid particles volume ratio, aging time on structure and properties of aluminum alloy surface hybrid composites layer via FSP. The results are as follows:1) In traversing speed of 45 mm/min, the crack defects on the surface of composite layer could disappear gradually with increasing the penetration depth of stir shoulder. Finally, in the penetration depth of 1.1 mm, the FSP specimen surface quality was acceptable, and there was not any crack. It shows that the tunneling cavity and particles agglomeration were disappeared easily and particles distribution were relatively uniform with increasing the number of FSP pass. In the same pass, the faster traversing speed, the more easily particles agglomeration appeared. With the weight added mixed particles increasing, the greater particles distribution area was, the more uniform particles distribution was, and the less agglomeration appeared. It was founded that in the weight of mixed particles of 0.35 g, the particles distribution was most homogenously. With the addition Mo S2 particles into Si C particle, the Si C particles in the cross‐section were uniformly dispersed and the agglomeration was reduced.2) With aging time increasing to 120 h, the lowest hardness of alloy surface was 164 HV. It is found that its low hardness led to more uniform plastic flow of the sample, which showed excellent sliding wear resistance because of the less agglomeration and more uniform distribution of the particles in the sample.3) When the condition of the rotational speed, transverse speed, the hybrid particles weight, the number of FSP pass were found to be 1200 rpm, 25 mm/min, 0.4 g, 4, respectively, the separate addition of Si C or Mo S2 particles resulted in agglomeration and inhomogeneous particles, and surface hardness was unstable. The mean hardness of the FSP specimens was 141±19.95 and 144±19.68 HV, respectively. The hardness of(VSi C:VMo S2=2:1)/FSP specimen were more stable than those of other composites, due to the uniform distribution of the particles in the sample, and the mean hardness was 124±4.02 HV.4) The wear tests show that adhesion and abrasive wear were mainly occurred in the composite layer, with fatigue and oxidation wear accompanied. In initial wear stage, surface composite layer showed plowed wear, leading to increase friction coefficient and worn seriously. In middle and later wear stage, antifriction and wear resistance particles were distributed in wear scar, which reduced friction coefficient; When the condition of the rotational speed, transverse speed, the hybrid particles weight, hybrid particles volume ratio, the number of FSP pass were found to be 1200 rpm, 25 mm/min, 0.4 g, 2:1, 4, respectively. Wear volume of the FSP specimen was 0.590±0.12mm3. Wear resistance was better due to the little agglomeration and uniform distribution of the particles.5) Under the conditions mentioned above, the specimen broken in heat affected zone(HAZ) which occurred weak necking was oriented to ductile fracture. The value of its ultimate tensile strength(UTS) and strain to failure were 340 Mpa, 13.67 %. From the tensile tests, the mainly reason for fractured specimens were as follows: serious mixed particles segregation in the cross‐section, lots of voids in the stir zone structure of FSP specimen, as well as the boundaries of HAZ were clear. |
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