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On the significance of intercritical annealing time in governing mechanical properties of lean composition dual-phase steel

Khorasani Fatemeh, Jamaati Roohollah, Aval Hamed Jamshidi

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e105, 2023

EN

In this study, the significance of intercritical annealing time in governing mechanical properties of lean composition dual-phase steel was investigated. The dual-phase steel was produced by 40% asymmetric cold-rolling followed by intercritical annealing at 860 °C for 1, 5, 10, and 20 min and water-quenching. It was found that in the 860-5 and 860-10 samples, island martensite forms at grain boundaries in the ferrite matrix and produced a chain-like structure. The martensite fraction increased by increasing the holding time of intercritical annealing from 1 to 10 min. Further increasing the holding time to 20 min, decreased the fraction of martensite. Increasing the martensite fraction reduced the carbon content of martensite, resulting in decreasing the hardness and strength but improving the ductility and formability of the martensite. The yield point phenomenon (YPP) was not visible in the dual-phase samples. The 860-1 and 860-20 DP steels revealed two-stage hardening behavior, while the 860-5 and 860-10 DP samples exhibited a three-stage behavior. The fracture surface of all samples consisted of many small and large dimples, implying ductile fracture. It was concluded that the α/α´ decohesion mode occurs when the martensite fraction in the microstructure was high enough.

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Effect of single roll drive cross rolling on the microstructure, crystallographic texture, and mechanical behavior of Al–Zn–Mg–Cu alloy

Kazemi-Navaee Amir, Jamaati Roohollah, Aval Hamed Jamshidi

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e41, 2022

EN

In this work, the effect of single roll drive cross rolling on the microstructure, crystallographic texture, hardness, tensile properties, and fracture behavior of AA7075 aluminum alloy was investigated. It was found that with increasing the thickness reduction, the grain size reduced and the average width of grain for the 40% deformed sample decreased to 3.7 ± 0.4 µm. Due to the nature of the cross-rolling process, several X-type shear bands were observed after 40% deformation. The recrystallization texture is notably intensified to its highest value of 4.4 × R, after only 20% cold deformation due to the occurrence of continuous dynamic recrystallization (CDRX). The intensity of recrystallization texture sharply dropped to its lowest value of 2.7 × R. This was due to the rotation of Goss-orientated new grains in the 20% deformed sample toward copper orientation during 40% rolling. With increasing the thickness reduction, the overall texture intensity significantly reduced owing to the nature of the cross-rolling process in which the rolling direction rotates 90° after each 10% strain. Two texture transitions were observed along τ fiber: rolling (copper) texture to recrystallization (Goss) texture after 20% thickness reduction and recrystallization to the rolling texture after 40% deformation. The hardness and strength increased by increasing the thickness reduction, while the ductility decreased. After a 40% thickness reduction, yield strength significantly increased from 138.3 ± 4.4 MPa (for initial sample) to the highest value of 580.5 ± 11.5 MPa, demonstrating 320% increment, in the 0° direction. This increment for 45° and 90° direction was 265% and 337%, respectively. By 40% rolling, the value of in-plane anisotropy (IPA) remarkably decreased to its lowest value of 3.4% due to texture weakening. With increasing the rolling reduction to 20%, the severity of Portevin–Le Chatelier (PLC) increased in the flow curves due to the occurrence of CDRX and also strengthening of the rotated cube {001} < 110 > and E {111} < 110 > components. With increasing the rolling reduction, the size of cleavage facets and the severity of delamination increased, and the number and depth of dimples decreased.

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Effect of friction surfacing parameters on the microstructural, mechanical properties, and wear characteristic of Al‑Cu‑Mg alloy coating reinforced by nickel aluminide

Farajollahi Ramezanali, Aval Hamed Jamshidi, Jamaati Roohollah

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e75, 1--18

EN

This research has studied the microstructure, mechanical properties, and tribological properties of AA2024-Al3NiCu composite coating fabricated by friction surfacing. The Al3NiCu intermetallic was created in the aluminum matrix by adding nickel during the stir casting process and then performing the homogenization treatment. The results showed that with increasing the axial feeding rate from 87.5 to 125 mm/min and the rotational speed from 600 to 800 rpm, the coating efficiency grew up to 79%. Moreover, no significant microstructural differences (grain size, precipitate size, and morphology) were observed in different parts of the coating. Applying the coating at a rotational speed of 800 rpm, a traverse speed of 125 mm/min, and an axial feeding rate of 125 mm/min raised the hardness and shear strength of the AA2024 aluminum alloy substrate by 17% and 21%, respectively, while lowering its wear rate by 37%.

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Characterization of microstructure, corrosion, and tribological properties of a multilayered friction surfaced Al–Mg–Si–Ag alloy

Pirhayati Parisa, Aval Hamed Jamshidi, Loureiro Altino

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e176, 2022

EN

In this research, an Al–Mg–Si–Ag multilayered coating with different amounts of silver additive was deposited on the AA2024 substrate using the friction surfacing process to investigate the microstructure, corrosion, and wear characteristics of the structure. The results showed that the silver-containing coating layer had a lower deposition rate and efficiency than coating without the silver additive. Owing to the lower temperature than silver-free coating and the presence of silver-rich particles acting as a barrier to grain boundary movement, no significant difference was found in grain size of different layers of the silver-containing coating. After aging heat treatment of the silver-containing coating, the Q (Al4(Cu, Ag) Mg4Si4) precipitates were formed as part of the silver-rich particles began to dissolve. After aging heat treatment, the top layer of the silver-containing coating showed 16% higher hardness than the AA2024 substrate. The wear rate of coating containing 13 wt% silver was 37% lower than the AA2024 substrate. The corrosion current density was reduced by approximately 97% and 99% in the silver-containing sample as compared to the sample devoid of silver and AA2024 substrate. With increasing silver content in the coated layer, the wear mechanism transitions from a combination of abrasive and adhesive wear mechanisms to an abrasive wear mechanism.