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Showing 23 results for Aluminum
Determination of the Modified Hall-Petch Equation Constants and the Relationship Between the Microstructure and Mechanical Properties of AS7U3G Alloy
M. Lashani Zand, B. Niroumand, A. Maleki,
Volume 37, Issue 4 (3-2019)
Abstract
Mechanical properties of the alloys are a strong function of the average silicon particles size and the secondary dendrite arm spacing (SDAS). Modified Hall-Petch equation expresses the effects of these two microstructural parameters on the yield strength and ultimate tensile strength of the Al-Si based alloys. These microstructural parameters depen on parameters such as chemical composition, cooling rate and melt treatment. In this study, the effect of cooling rate on the  equation constants of the alloy were determined. For this purpose, the alloy was poured at 750 °C in three different molds including a sand mold, a preheated steel mold, and a water cooled steel mold. The Thermal and microstructural analysis showed that the cooling rate in the metal mold was 15.7 times higher than that of the sand mold, which resulted in a decrease of the SDAS from 54 micrometers to 17 micrometers. It was also found that by reducing the SDAS from 45 micrometers to 17 micrometers, the yield strength and tensile strength were increased by 16.5% and 6.5%, respectively. The modified Hall-Petch equation constants and the microstructure-mechanical properties relationships were then established by the microstructural and tensile test studies.

Mechanical Properties and Spring -Back Investigation in Creep Age Forming Process of 7075 Al Alloy
H. R. Shahverdi, R. Alipour Mogadam,
Volume 38, Issue 2 (9-2019)
Abstract
Creep age forming (CAF) process is a novel metal forming method with major benefits including improved mechanical properties and cost reduction for aviation industry applications. CAF happens due to creep phenomenon and stress-release during the artificial aging of heat-treatable  aluminum alloys. In this work, the creep age forming of 7075 Aluminum alloy at 120, 150 and 180 °C for 6, 24 and 48 h was done; tensile and hardness tests were used to characterize the samples. Results on spring-back revealed that it was influenced by time and temperature;  by increasing the time and temperature, it was reduced from 54.1 to 39.51. Mechanical property evaluation also showed that by increasing the time, the strength and hardness could be enhanced due to microstructural evolution and precipitation during the CAF process. According to the mechanical and CAF results, two samples were selected as the optimum ones and their work hardening behavior and fracture surfaces were investigated

Investigation of the Effect of Adding Aluminum Trihydrate (ATH) Particles on Electrical and Hydrophobic Properties of Two-Part RTV Silicon Rubber
A. Zolriasatein, S. Navazani, M. Rezaei Abdadchi, N. Riahi Noori ,
Volume 39, Issue 3 (12-2020)
Abstract
In this paper, the effect of adding aluminum trihydrate (ATH) on electrical (including dielectric constant, dielectric loss and strength, volume and surface resistivity) and hydrophobic properties of two-part room temperature volcanized (RTV) silicone rubber resin coatings were investigated. For this purpose, the RTV-ATH nanocomposite was made by physical mixing and its electrical and hydrophobic properties were compared with those of pure RTV. The results showed an increase in the dielectric constant (from 3.11 to 4.13), the dielectric loss (by ~ 0.06) and the dielectric strength (by ~ 4 KV/mm) of the RTV-ATH composite compared to the pure RTV. Moreover, ATH increased volume resistivity and reduced the surface resistivity of composite coatings. On the other hand, by spraying of coatings, no improvement in the hydrophobicity class of composite coating compared to pure RTV was observed and both samples were standardized in the HC2 standard class. Structural analysis of samples was performed by X-ray diffraction, optical microscopy and scanning electron microscopy and the presence of the main phases in them was confirmed.

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