دانلود رایگان مقاله مطالعه ارسال غلتک تغییر شکل پلاستیک آلیاژ سیلیکون آلومینیوم منگنز

abstract

Constrained groove pressing (CGP) as a severe plastic deformation (SPD) technique was applied on Al-Mn-Si sheets. In the following, direct- and cross-rolling were employed as supplementary processing in order to investigate the rolling-direction effect on CGPed sheets. The in-depth characterization of microstructural evolutions were employed using polarized light microscope and scanning electron microscope. Williamson–Hall analysis method was applied on X-ray diffraction (XRD) patterns of specimens. Analysis of XRD results revealed that post-rolling of CGPed sheets induced dynamic recrystallization (DRX) due to massive dislocations’ accumulation which follows by crystallite growth. The largest crystallite size which was 619 nm achieved after direct-rolling through the rolling strain of 1.27. Maximum acquired peak intensity ratio for rolled sheets was for (220) crystallographic plane similar to annealed one. Also, post-rolling had altered the distinguished plane from (111) for CGPed sheets into (220). Mechanical characteristics of specimens were examined using hardness and tension tests. Based on the obtained results, direct-rolling of CGPed samples was more susceptible for strength enhancement compared to cross-rolling. Optimum achieved values for yield and ultimate tensile strength were 155 and 197 MPa, respectively. Rolling in the both longitudinal and cross directions had almost similar effect on the final attained hardness.

4. Conclusions

Rolling the CGPed Al-Mn-Si specimens as supplementary deformation process was successfully executed up to severe strains. Compact lamellar structure contained elongated grains was achieved by increasing the rolling strain. Using rolling as post processing on CGPed sheets accelerated the microstructural refinement. Additionally, analogy of crossand direct-rolling pointed to higher dislocation accumulation due to rolling of CGPed Al-Mn-Si alloy accompanied by dynamic recrystallization. The minimum crystallite size of 431 nm which was achieved by second pass of CGP was increased to 619 nm and 593 nm through direct- and crossrolling by 1.27 strain, respectively. Based on XRD patterns, it was concluded that post-rolling had not distinctive effect on peaks' pattern and (200) planes preserved the maximum intensity ratios in rolled specimens as for annealed one; however, CGP changed the pattern in such a way that (111) had the maximum intensity ratio. Post-rolling of CGPed specimen changed the material's crystallographic characteristics since intensity ratios for (220) plane enhanced. Characteristic peaks in both direct and cross directions were insensitive in confronting with the rolling strain increment. Changing the rolling direction had not any significant effect on microstructural and mechanical characteristics of annealed Al-Mn-Si specimens since the direct-rolling of CGPed aluminum led to improved mechanical properties and finer microstructure compared to those achieved through cross-rolling.