Tensile Properties and Microstructures of a 2024-T351 Aluminum Alloy Subjected to Cryogenic Treatment

Abstract

Abstract:The aim of this study was to investigate the effects of the cryogenic treatment (CT) using liquid nitrogen on tensile properties and microstructures of the 2024-T351 aluminum alloy. Tensile tests were carried out, and tensile fractures were observed using a scanning electron microscope (SEM). The microstructure evolution of 2024-T351 subjected to CT was also studied using both an optic microscope (OM) and a SEM. The components of the second phase were tested with an energy dispersive spectrometer (EDS). The results showed that both the ultimate strength and the yield strength of the 2024-T351 aluminum alloy could be improved through CT without the sacrifice of elongation. In addition, tensile fractures showed that the plasticity of 2024-T351 aluminum might also be improved, as the dimples in the fracture of the CTed specimens were markedly more uniform compared with the untreated specimen. The phenomenon of grains refinement (GR) was found through microstructure observation. It was also found that the second phases were distributed more uniformly after CT. A conceivable mechanism concerning the shrinking effect and crystal grain movement was raised to explain the experimental phenomena. The effects of CT on residual stress in the 2024-T351 aluminum alloy are discussed herein. Measurements showed that tensile residual stress in 2024-T351 was removed, and slight compressive residual stress was generated after CT. This may also contribute to the improvement of the tensile properties of the alloy.

Effect of Alternating Magnetic Field on the Fatigue Behaviour of EN8 Steel and 2014-T6 Aluminium Alloy

“…The treated sample contains more ductile dimple features with diverse sizes similar to those discussed by researchers who investigated the fractography of steels and aluminium alloys [21,22]. A few quasi-cleavage features are visible in both of the treated alloys that exhibit ductile torn edges [23] or peaks [24]. The fracture surface of untreated EN8 steel has more secondary cracks similar to those observed by Zhang et al [25] compared to the treated condition.…”

In-situ icing and water condensation study on different topographical surfaces

“…AR-Al substrates have relatively high elastic modulus (72.4 GPa [31]) as compared with PDMS (2.4 MPa [32]), and have surface topographic pattern (~Ra 0.9 μm) as shown in Figure 1a and 1c. AR-Al substrates surface has a considerable heterogeneous solid surface (rougher asperities) [33,34], which may acts as icing seeds by reducing activation energy for ice nucleation [35].…”

Effects of Cryogenic Treatment on the Microstructure and Residual Stress of 7075 Aluminum Alloy

“…For example, the treatment combining CT and repaid heating can relieve about 71% of residual stress [11]. In addition, CT can improve the microstructure and mechanical performance of aluminum alloy [12][13][14][15]. As investigated by Volker et al, CT increased the fretting wear resistance and fretting fatigue life of aluminum alloy, owing to the formation of nano-scaled GP-zones, and Li et al demonstrated the viability of this phase transformation by first-principles calculations [12,13].…”

“…It was proved that CT promoted the re-dissolution or dispersed precipitation of the GP-zones in the welded joints of 2024 Al alloy [13,15]. In addition, the mechanical properties of Al alloy can be successfully improved, and the influence of mechanical properties is strongly affected, by the material state before CT [13,14,16]. In a bibliographic review completed by Delprete and Baldissera [17], the microstructural influences of CT on microstructure and mechanical properties were analyzed comprehensively.…”