Papers by Keyword: Surface Mechanical Attrition Treatment

Abstract: Cu and Cu-30wt.%Zn alloys with stacking fault energies (SFEs) of 78 mJ/m² and 14 mJ/m² were processed by surface mechanical attrition treatment (SMAT) at room temperature and liquid nitrogen (LN) temperature, respectively. The effect of SFE and deformation temperature on tensile properties of these samples was investigated. The tensile testing results indicated that the yield strength and uniform elongation of these samples enhanced simultaneously with decreasing SFE. Meanwhile, the LN-SMAT processed samples exhibited remarkably higher strength and slightly lower ductility compared to those processed at room temperature. The SFE affected the deformation mechanisms of metals greatly. X-ray diffraction (XRD) measurements indicated that the twin density increased while the average grain size decreased with SFE decreasing, and twinning became the dominant deformation mechanism. The relationship between microstructure and mechanical property is also discussed.

Abstract: Surface Mechanical Attrition Treatment (SMAT) is a recent process that enables to nanocrystallise the surface of metallic alloys. It can thus enhance mechanical properties of the treated material by inducing a grain refinement down to the nanometre scale, in the top surface layer. This nanocrystallisation process leads to different effects that were successively studied on several metallic materials. In the present work, investigations are carried out on the modelling of SMAT. A simulation of the shot dynamics is performed using different process parameters, with the aim to obtain the impact velocity field on the treated surface. This field is then used as an input for a finite element model to predict the induced grain refinement. The evolution of the micro and nanostructures are then calculated using a micromechanical approach, which takes into account the dislocations and their interactions. Coupled with a finite element analysis, this approach enables to deduce the influence of the process on the macroscopic material properties, whatever the geometry of the sample.

Abstract: The texture evolution of the pure iron sample after the surface mechanical attrition treatment (SMAT) was investigated by means of electron backscattering and X-ray diffraction (XRD) analysis. Experimental observations indicated that four sections along depth were formed in the pure iron sample during the SMAT, i.e., nanostructured regime in the surface layer, submicro-sized, micro-sized and plastic deformed regime. Compared to the microstructure of sample, texture analysis was performed. It can be found that the <110>//ND fiber texture is the prominent texture. A strong orientation of (110)[11] along the <110>//ND fiber was formed in the plastic deformed regime, and as the depth from the top surface decreases, <110> //ND fiber texture intensity increases. The maximum intensity was reached in the micro-sized regime, and then it start to reduce. In the nanostructured regime, <110> //ND fiber texture nearly disappear.

Abstract: The texture evolution in the plastic deformation layer of the pure iron sample after the surface mechanical attrition treatment (SMAT) was discussed through electron backscattering and X-ray diffraction (XRD) analysis. The results showed that: the surface layer of the iron sample can be subdivided into four sub-layers along the depth from the top surface: nano-sized regime, submicro-sized regime, micro-sized regime and deformed coarse-grained regime. Nano-sized regime possesses random crystallographic orientations. But in submicro-sized regime and micro-sized regime, the //ND fiber texture is the prominent texture with a strong orientation of (110)[1-11]. Increasing treatment time during SMAT process does not change the components of texture in plastic deformation layer, only strengthen their orientation density.

Abstract: Commercial Cu_0.62Zn_0.38foil was subjected to surface mechanical attrition treatment (SMAT) processing. The original and SMAT Cu_0.62Zn_0.38 foils are thermally oxidized at 500°C under N₂-5%O₂ gas environments, at a pressure of 1 atm for 3 hours. The oxidized specimens were characterized with a scanning electron microscope, an X-ray diffractometer. It is found that nanosheets are easily formed on the SMAT specimen surface. The favorable formation of nanosheets relates to twin–matrix lamellae structure.