فهرس المقالات Fractography

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  1 - Microstructural Investigations and Fracture Analysis of a Multi-Layer Al Panel of a Crashed Aircraft
  H.R. Faridi A. Momeni M. Mohammadpour V. Sarfarazi
  In this paper, the failure analysis was performed on a crashed airplane trunk sample. Received sample was composed of five different layers; Al 2024 as outer layer, a nearly pure Al clad, an anodized layer, an isolating material and the alloy 413 as interior layer. Macr أکثر

  In this paper, the failure analysis was performed on a crashed airplane trunk sample. Received sample was composed of five different layers; Al 2024 as outer layer, a nearly pure Al clad, an anodized layer, an isolating material and the alloy 413 as interior layer. Macro and micro-cracks in the sample were mostly initiated from the areas close to or around the rivets. These cracks initiated in anodized layer, got through the cladding and entered into the outer Al 2024. Few corrosion sites similar to crevice were also observed behind the rivets and between isolating and cladding layers. It was found that the crevice corrosion and fatigue were responsible to form micro-cracks at these sites. Microstructural observations of Al 2024 layer showed that the micro-cracks were mostly initiated form inside out then they progressed through the interfaces of second phase particles and the matrix. It was found that larger particles were in favor of crack propagation along their interfaces. Second phase large particles are attributed to over-aging of trunk sample which was subjected to excessive heat from the engines. تفاصيل المقالة
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  2 - Fabrication of AA1060/Al2O3 Composites by Warm Accumulative Roll Bonding Process and Investigation of its Mechanical Properties and Microstructural Evolution
  M. Heydari Vini P. Farhadipour
  Recently accumulative roll bonding (ARB) has been used as a novel method to produce particle reinforced metal matrix composites. The accumulative roll bonding as a severe plastic deformation (SPD) rolling procedure aimed at enhancing the mechanical properties of metals أکثر

  Recently accumulative roll bonding (ARB) has been used as a novel method to produce particle reinforced metal matrix composites. The accumulative roll bonding as a severe plastic deformation (SPD) rolling procedure aimed at enhancing the mechanical properties of metals and alloys. The process consists in rolling series of overlapped sheets with a thickness reduction ratio (e.g. 50%). In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Aluminum Metal Matrix Composite (AMMC: AA1060/-5% Al2O3). AA1060 strips were roll bonded as alternate layers up to 5 rolling passes with 300°C preheating for 5 minutes before each pass. The microstructure and mechanical properties of composites have been studied after different Warm- ARB passes by tensile test, Vickers micro hardness test and scanning electron microscopy (SEM). The results demonstrated that adding alumina particles into AMMCs improves both the strength and tensile toughness of composites. Moreover, the fracture surfaces of samples after the tensile test have been studied during various ARB cycles by scanning electron microscopy (SEM). Also, the results showed that mechanical properties such as tensile strength and average Vickers micro hardness improved with increasing the number of warm ARB cycles. Also, the elongation and tensile toughness of samples dropped in the primary cycles and improved in continuing with increasing the warm ARB cycles. Finally, warm ARB process would allow producing particle reinforced with good mechanical properties. تفاصيل المقالة
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  3 - Mechanical Properties and Microstructural Evolution of AA5083/Al2O3 Composites Fabricated by Warm Accumulative Roll Bonding
  Mohammad Heydari Vini M. Sedighi Mehdi Mondali
  In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Metal Matrix Composite (MMC: AA5083/-5% Al2O3). Starting materials were roll bonded as alternate layers up to 5 rolling cycles with 300°C preheating for five minutes before ea أکثر

  In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Metal Matrix Composite (MMC: AA5083/-5% Al2O3). Starting materials were roll bonded as alternate layers up to 5 rolling cycles with 300°C preheating for five minutes before each cycle. The microstructure and mechanical properties of composites have been studied after different Warm- ARB cycles by tensile test, Vickers micro hardness test and scanning electron microscopy (SEM). The results revealed that during higher Warm- ARB cycles, breaking the layers of alumina particles led to the generation of elongated dense clusters with smaller sizes. This microstructural evolution led to improvement in the hardness, strength and elongation during the Warm- ARB process. The results demonstrated that the dispersed alumina clusters improved both the strength and tensile toughness of thecomposites. Finally, Warm- ARB process allowed producing metal particle reinforced with high uniformity, good mechanical properties and high bonding strength. تفاصيل المقالة
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  4 - Microstructure Investigation and Mechanical Properties of Resistance Upset Butt Welded Ti-6Al-4V Alloy
  Mahmood Sharifitabar
  10.30495/admt.2020.1891939.1170
  In the present study, resistance upset butt welding was used as a solid-state process for joining Ti-6Al-4V alloy. Results showed that melting and subsequent solidification of the alloy at the joint interface promoted the development of a cast microstructure along with أکثر

  In the present study, resistance upset butt welding was used as a solid-state process for joining Ti-6Al-4V alloy. Results showed that melting and subsequent solidification of the alloy at the joint interface promoted the development of a cast microstructure along with some pores. However, by applying the constant upset pressure of 1.62 MPa, the pore volume fraction decreased considerably with decreasing the welding current from 110 A/mm2 to 55 A/mm2. Hardness test results showed that the weld interface and the base material had the highest (352 HV) and the lowest (318 HV) values, respectively. The microstructure of the interface consisted of ά martensite and Widmanstätten laths. The tensile strength of the joints varied between 550 and 883 MPa depending on the welding parameters used. In the optimum condition, the maximum strength of the joint was about 94% of the base metal strength. Fractography of samples confirmed that the formation of pores deteriorated the strength of the joints. تفاصيل المقالة