Dr Seyed Mahdi Rafiaei, Eng. Gholamhosein Eslami,
Volume 7, Issue 2 (Journal OF Welding Science and Technology 2022)
Abstract
In this research, Ti-6Al-4V alloy sheet with a thickness of one millimeter with butt joint design was welded by tungsten-gas arc welding process using pulse current (PCGTAW) and using AMS 4954G filler metal. In this study, the effect of pulse system frequency on microstructure and mechanical properties was investigated by optical microscopy, Vickers hardness and tensile strength tests. In the non-frequency welding sample, due to the lack of pulse current and lower cooling rate of the molten pool, the formation of large amounts of soft phases of the Weidmann-Statten layer in the weld metal region is possible. Finally, in this method, the lowest average hardness of 341 Vickers was obtained. The experimental results showed that using pulsed current and increasing the pulse frequency up to 450 Hz increased the cooling rate of the molten pool, followed by increasing the amount of martensitic phase α 'in the form of a basket in the weld metal region and finally increasing the average microhardness in this region. In other words, using the maximum frequency led to a significant increase in hardness up to 367 Vickers in the weld zone. Finally, using the tensile strength test, it was shown that in all the samples, failure occurred from the base metal area, which was a very good phenomenon due to the proper welding quality of the samples.
L. Gadami Domabi, S. M. Rafiaei, S. Jahanbazi Gojani,
Volume 9, Issue 1 (Journal OF Welding Science and Technology 2023)
Abstract
In this paper the production of chitosan and polylactic acid polymer scaffolds containing zinc oxide particles was carried out through the 3D printer method. Zinc oxide particles were processed through combustion synthesis method. According to the XRD results, the produced oxide has a high phase purity, and the evaporation of volatile impurities and the increase of crystallinity happened via performing the calcination process. In the X-ray diffraction pattern of PLA/ZnO/Chitosan, the broad peak in the range of 10-25 degrees indicates the amorphousness of the background polymer, and with the addition of ZnO, sharp and powerful peaks have appeared in the graph. The SEM images of zinc oxide synthesized by combustion method also showed that the size of ZnO nanoparticles is approximately 50 nm, while after the calcination heat treatment, the size of the particles increased greatly and reached an average size of 130-160 nm. Finally, the microscopic images obtained from the surface of scaffolds possessing 10% zinc oxide, 5% chitosan and polylactic acid showed that by optimizing the 3D printer, ZnO particles are uniformly dispersed in PLA/Chitosan polymer field.
