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تاثير اضافة الكالسيوم على البنية المجهرية والخواص الميكانيكية لسبيكة Al - Cu - Mg == Effect of Ca Addition On The Microstructure And Mechanical Properties of Al - Cu - Mg Alloys
Author name:
نور صباح توفيق
Supervisor name:
منذر محمد راضي
General topic:
Production engineering metallurgy and materials
Specific topic:
Metals Engineering
Degree:
Master
University:
University of Technology
Language:
English
University location:
Baghdad
First pages:
50T194 - p.pdf
Abstract:
في هذه الرسالة تم دراسة تاثير اضافة عنصر الكالسيوم بنسب مختلفة ) 3.0 المجهرية والخواص الميكانيكية لسبيكة) المنيوم - نحاس - مغنيسيوم ( , حيث تم انتاج هذه السبائك باستخدام والتي تتضمن )المعاملة المحلولية, )? السباكة الرملية وعوملت حراريا باستخدام المعاملة ا | In this thesis ,the effect of pure Ca element addition in different percents of (0.3,0.6,0.9%) on the mechanical properties of Al - Cu - Mg alloy were studied.The Alloys were produced using sand casting and heat treated using T6 which involve [solution treatment , quenching , artificial aging ], aging process were carried out at 220? C for different periods of time ranging between (5min to5hr).Also the work involves a study on the effect of Ca addition on both grain size as well as the resulting phases before and after heat treatment, samples were examined using optical microscope, Scanning Electron microscope ,X - Ray diffractometer and image - J to estimate the average grain size.The results of hardness and tensile tests for 0.6% Ca and 4hr aging shows the best response as compared to the other alloys. The hardness and strength values have been changed from (78.29HV)(110.57Mpa) during (30min)at 220?C for non - Ca content alloy to(125.9HV)(164.2Mpa) for 0.6%Ca alloy. X - Ray diffraction , results shows the basic phase that forms is Al2CuMg (S??, S? phase) which is considered as the main strengthening phase in AL alloys, and it was found that Ca addition leads to form (Al4Ca) and (Al2Ca)which delay the alloy response to precipitation hardening by delaying the formation of (S)phase. SEM images showed a large and small dimple structure and broken or cracked Al - Ca compounds particles.This indicates that the fracture was ductile fracture in the Al matrix and brittle in these compounds ,.Also presence of microvoids (porosity) on the fracture surface is formed at the interfaces between Ca compounds and Al matrix enhanced the crack propagation through their center. The presence of the secondary phases precipitates (Al2CuMg ,Al2Ca and Al4Ca) in the fracture surface also contributed to ameliorate the mechanical properties by increasing the bonding of the matrix and reduced the ductility.Also Ca addition in the range of (0.3 - 0.6%) gives rise to grains refining ,While increasing Ca content up 0.9%wt coarsing the grains, which leads to decrease the hardness and tensile strength, From these results the decrease in tensile strength with increasing Ca content over 0.9% seems to be attributed to the reduction in elongation caused by the occurrence of micro porosity due to Ca addition.
