Share
تاثير التشكيل على البنية المجهرية وسلوك البلى للمواد المعدنية المتراكبة النانوية Al2O3 / A356 == The Role of Forming On Microstructure And Wear Behavior of Metal Nano Composite Al2O3 / A356
Author name:
مروان باسل حسين
Supervisor name:
نوال عزت عبد اللطيف | عقيل ظاهر صبحي
General topic:
Production engineering metallurgy and materials
Specific topic:
Metals Engineering
Degree:
Master
University:
University of Technology
Language:
English
University location:
Baghdad
First pages:
50T164 - p.pdf
Abstract:
في هذا البحث تم تحضير المواد المركبة النانوية اساس معدني (A356/Al2O3) باستخدام تقنية (rheocasting) ومن ثم تم اجراء عملية التشويه على الساخن عند درجة حرارة °250 م.في البداية تم صهر السبيكة A356 في درجة حرارة °730 م بعدها تم تبريدها الى درجة حرارة الشبه ص | In the present work Al2O3/A356 nano composites have been prepared using rheocasting technique, the nano composites were then processed using hot deformation at 250 °C.Firstly A356 matrix alloy was melted at about 730 °C, the superheated molten alloy was allowed to cool to the semi - solid temperature at 600 °C, then Al2O3 nano - particles with different size (10,20) nm and different weight percentages (1 and 2)%wt were added inside the vortex formed due to stirring , hot deformation carried out with different ratio 30% and 40% at the temperatures of 250 °C and strain rates 0.1 s?1. The produced nano composites samples were characterized using optical and scanning electron microscopy ,X - ray diffraction , hardness test and wear test using pin on disc apparatus. The results of microstructural observations showed that the Al2O3 nano particles cluster mostly near the grain boundaries and form a band surrounding the grain boundaries. The dendritic structure of ? - Al phase is fragmented and the ? grains became more uniform and smaller than their corresponding as - cast 356 alloy. On other hand the microstructures of nano - Al2O3/A356 composites after casting and hot deformation at 250°C, showed modification of ? - Al and Si eutectic. The columnar dendrites ? - Al phase changed to the nearly equiaxed grains or globular morphology. The results of hardness test showed that the nano Al2O3/A356 composite were exhibited higher hardness than the as - cast A356 alloy The nano - composites hardness, increase with increases the size and increases in weight percentage of the Al2O3 nano - particles, and with increasing percentage deformation. The result of wear test showed that the hot deformed nano Al2O3 /A356 composites have greater wear resistance compared with hot deformed A356 alloy. Furthermore, with increasing the particle size and the percentage of Al2O3 nano particles, wear rate will decrease. The results also revealed that the optimal results was achieved at the nano - composites containing 20nm Al2O3 particles after hot deformation with 40%. SEM studies of the worn surface of nano composites showed that the main wear mechanism was oxidative in conjunction with metallic wear.
