جوشكاري اصطكاكي اغتشاشي كامپوزيت نانو ساختار Al-Al2O3 توليد شده با فرايند نورد تجمعي و ارزيابي خواص اتصال

چكيده انگليسي :

107 Friction Stir Welding of Al Al2O3 Nonostructure Composite Fabricated by Accumulative Roll Bonding and Evaluation of Joint Properties Hamed Adinehlou h adinelo@ma iut ac ir Date of submission 12 03 2012 Department of Material Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Morteza shamanian Shamanian@cc iut ac ir Ahmad Kermanpur A kermanpur@cc iut ac irAbstractParticulate reinforced aluminum matrix composites have recently become a major focus ofattention in aerospace motor sport and automotive industrial fields due to their several attractiveadvantages over conventional base alloys such as high specific stiffness and strength to weightratio at room or elevated temperatures Friction stir welding is a promising candidate for joiningparticulate reinforced aluminum matrix composites since this method is a solid state process therefore the formation of brittle solidification products are not easily produced the energy inputand distortion are significantly lower than in fusion welding techniques thus improving thewelding properties In this research Al 5Vol Al2O3 composite was produced after 10 cycles ofaccumulative roll bonding process Then the composites were friction stir welded using 9 differentwelding parameters including rotation speeds of 900 1120 and 1400rpm and welding speeds of 63 80 and 100mm min A K type thermocouple was used to record the temperature of the weld line This thermocouple was fixed in retreating side of the weld line On the other hand in order to studythe effects of welding tool at a specific welding parameter effects of four different pin profiles square triangular hexagonal and cylindrical were evaluated Microstructural and mechanicalassessments were performed using scanning electron microscopy tensile test and microhardnessmeasurements The fracture surfaces were examined and the mechanisms of fracture surfaces werealso characterized A uniform distribution was observed after 10 cycles of rolling while no porositywas seen in the matrix particle interface and adhesion of reinforcement particles to matrix wereimproved The mechanical properties of produced composites were better than those of pureannealed aluminum The initial composite showed ductile fracture with shallow dimples Someporosity and discontinuity was observed in the samples welded at low rotation speed of the 900rpmand welding speed of 63 80 and 100mm min because of inadequate heat input and weak stirringaction Here the mechanical properties were poor because of discontinuities in microstructure Byincreasing the rotation speed good weld faces were achievied because enough heat input wassupplied The samples welded at rotation speed of 1120rpm 100mm min with maximumrevolution pitch value Welding Speed Rotation Speed of 0 089mm r showed the highest value oftensile strength and hardness and the lowest value of elongation The samples produced at speed of1400rpm 63mm min with minimum revolution pitch value of 0 045mm r showed lowest tensilestrength and hardness value and the highest value of elongation Welded samples exhibited ductilefracture and initial shallow dimples become deeper because of heat input of welding process Theresults of four different pin profiles showed that the fragmentation and distribution of particles ismore desirable while square pin profile was used The effect of dynamic volume static volume ratioand pulsating stir of the pin profiles were played the main role in fragmentation and distribution ofparticles simoltaneously These two parameters had the highest value in square and triangular pinprofiles In this case the highest values of tensile strength hardness and elongation were achievedand it was related to square pin profile Keywords Accumulative Roll Bonding Friction Stir Welding fragmentation Revolution pitch Fractography pin profiles

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جوشكاري اصطكاكي اغتشاشي كامپوزيت نانو ساختار Al-Al2O3 توليد شده با فرايند نورد تجمعي و ارزيابي خواص اتصال

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