Results of temperature measurements during welding of 12.7 mm thick AA6061-T6 alloy plates by modified indirect electric arc (MIEA) are presented. This study describes the thermal cycles in the heat-affected zone (HAZ) and also in the fusion zone. Depending upon the position of the transducers, the maximum temperatures measured in the HAZ ranged from 308 to 6938C, these measurements were related with the tensile test results and the failure zone reported previously by the authors (Ambriz et al., S&I 2006;11:10 -17). It was observed that there is a decrease in the mechanical strength of the welded joints, due to the microstructural changes undergone by the AA6061-T6 alloy in which formation of the b 0 occurs according to the time -temperature transformation diagram. The inherent cooling conditions of the weld pool observed for the MIEA technique (single welding pass) have made it possible to establish the characteristics of solidification and microstructure for a specific cooling rate.
Grit blasting is a low cost surface modification treatment widely used to enhance mechanical fixation of implants through increasing their roughness. As a result of the severe surface plastic deformation, beneath the surface it produces additional effects such as grain size refinement, work hardening and compressive residual stresses, which are generally evaluated with destructive techniques. In this research work, the blasting induced effects by Al 2 O 3 and ZrO 2 particles and their evolution after annealing at 700ºC were evaluated in 316LVM (Low Vacuum Melting) stainless steel specimens using two non-destructive thermoelectric techniques (NDTT), the non-contacting and contacting thermoelectric power measurements. Microstructural analysis and microhardness measurements performed beneath the blasted surface reveals that the non-contact NDTT results correlate well with the reversion of the α'-martensite developed during blasting, whereas the contact NDTT results are closely related to the grain size refinement and work hardening and the expected evolution of compressive residual stresses. Potential of these techniques to monitor subsurface changes in blasting processes and others severe surface plastic deformation techniques are clearly envisaged.
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