Search

This work aimed to elucidate and compare the solidification characteristics of A356.2, A356.2/5% SiC, A356.2/5% Al2O3, and A356.2/5% ZrO2metal composites with and without adding Bi element by using the Fourier thermal analysis method. Microstructural and XRD analysis showed that reinforcement particles have been successfully embedded in the A356.2 alloy through the compo-casting route. Thermal analysis results show that the cooling rate of the A356.2 matrix alloy, as measured in the experimental set-up, was 0.8 °C/s and increased to 1.9 °C/s in the composites. The nucleation temperature of α-Al increased slightly (0.6 °C), and undercooling (8.9–11 °C) was observed for all composites. The nucleation temperature of the Mg2Si phase and solidus temperature of composites were lower than the A356.2. Moreover, the growth temperature and recalescence magnitude of eutectic Al-Si did not change remarkably. The solidification temperature range and solidification rate increased by 5% and 33%; however, the solidification time decreased by 21%. The solid fraction at the coherency point increased, which is associated with an expansion in the time difference between nucleation and the coherency point. However, adding Bi resulted in the depression of eutectic growth temperature and the refinement of eutectic Si. These data infer that the solidification kinetic of A356.2 and their composites are identical. It cannot be concluded that reinforcement particle acts as nucleation agents for both α-Al and eutectic Si.

Increasing dispersion stability is the main issue in recent research at magnetorheological (MR) fluids. The presentation of nanoparticle addictive in MR fluids is an effective method not only to increase dispersion stability but also increasing performance in MR fluids. In this study, the effect of hard magnetic CoFe2O4 nanoparticles addition on rheological properties and dispersion stabilization had been studied. Rheological properties were investigated using a rheometer at room temperature. The result showed that the addition of CoFe2O4 nanoparticles 1wt% in particles of MR fluids were improving the shear stress and viscosity of MR fluids. Both MR fluids with and without nanoadditives behaving like a Newtonian fluid at the off-state condition and act like Bingham fluid at the on-state condition. Moreover, MR fluid with CoFe2O4 additives had a higher sedimentation ratio than MR fluids without additives.

Magnetorheological (MR) fluid devices are now applied in various applications. Although a lot of studies have been discussed in long-term implementation of MR devices, only few studies have concerned on MR fluid application in valve operation mode, such as at MR valve. The experiments were conducted on a dynamic test machine in a custom MR damper with meandering MR valve. The experiment test was applied at continuous-load in long term-operation with parameters of 20 mm length of stroke, 0.4 Hz of frequency, 0.5 A of applied current and 175,000 cycles. The rheological properties of MR fluid were characterized using rotational and oscillatory shear rheometer. The result showed that the rheological properties of MR fluid changed after applied in long-term operation. The changed of MR fluid also investigated through morphological characteristics using SEM and EDX.

In this study, magnetorheological elastomers (MREs) were synthesized using silicone rubber (SR) as the matrix element interspersed with 70 weight percent of corroded carbonyl iron particles (CIPs). The CIPs were corroded in dilute hydrochloric acid (HCl) for 4 hours. The rheological properties related to MR effect were experimentally examined in the absence and presence of magnetic field at various current using a rheometer. The experimental results depicted the MR effect of the MRE with corroded CIPs decreased one-half, 27% as compared to the non-corroded samples, 58%. The correlation between the purity of CIPs and storage modulus of MR elastomer is examined in this study.

Since the mechanism of Sn-whisker growth is closely related with the behavior of deformation and recrystallization, understanding of the behavior is very important to establish the measure for mitigation of whisker growth. In this work, microstructural changes after heavy deformation by scratching were characterized by EBSD for a single crystal of β-Sn, and the following results were obtained. Three types of crystal grains appear immediately after the deformation; small grains in aggregation, large serrated grains and rim-grains. The small grains are considered to be formed by dynamic recrystallization. They continue to grow at a room temperature over a lengthy period of time. The large grain has a certain crystallographic relationship with the matrix where <100> axes of the large grain and the matrix are almost parallel to each other. The serrated boundaries of large grain are so stable that the large grain does not show a grain growth process. The stable boundary is considered to promote a continuous growth of whiskers.

Advantage of Al-Mg2Si metal matrix composite (MMC) is due to the particulate reinforced Mg2Si in the Al matrix that has improved mechanical properties of the in situ composite. In particular, the composite has been chosen as the structural material for automotive and aerospace components. The hypereutectic Al-Mg2Si composite should be comprised of two morphologies, namely primary Mg2Si and pseudo-eutectic Al-Mg2Si phase. However, as-received commercial Al-20Mg2Si-2Cu in situ composite contained a wide range of elements that affect the resultant microstructure of the in situ composite. In fact, four different morphologies have been identified in the in situ composites. The first phase is dark facet primary Mg2Si particles, surrounded by pseudo-eutectic Al-Mg2Si phase in lamellar structure. Along the eutectic boundary is the formation of needle-like Al5FeSi intermetallic and the phase is surrounded by Al5Mg8Si6Cu2+Al2Cu as last phase nucleated. Optical micrograph, SEM imaging, EDX analysis and elemental mapping have revealed these phases correspond to shape of morphologies and respective molecular compound.

This work investigated the microstructure evolution, tensile, impact, hardness, and sliding wear properties of an Al–20Mg 2 Si–2Cu in situ composite treated with different Bi contents. The desired modification of primary Mg 2 Si particles was achieved with the addition of 0.4 wt% Bi. Increasing Bi beyond 0.4 wt% resulted in a loss of modification, possibly due to the formation of Al 8 MgBiSi 4 compound before the precipitation of the primary Mg 2 Si. Additionally, the structure of the pseudo-eutectic Mg 2 Si was transformed from plate to fibrous, which was consistent with decrease of growth temperature extracted from the cooling curve thermal analysis. Addition of Bi had an effect on the morphology of Al 5 FeSi (β), Al 2 Cu (θ) and Al 5 Cu 2 Mg 8 Si 6 (Q) intermetallic compounds. The tensile strength, elongation percentage, impact toughness, and hardness increased by 6%, 13%, 75%, and 23%, respectively, due to modification of both the primary and eutectic Mg 2 Si crystals. The tensile and impact fracture surfaces showed fewer decohered particles in the Bi-treated composite. The enhancement in wear resistance of the Bi-treated composite could be attributed to solid lubricant function of insoluble soft Bi phase and modification effects on Mg 2 Si particles. [ABSTRACT FROM AUTHOR]

Owing to its beneficial material properties, Al-Mg2Si in-situ composite has recently received wide attention and application in the manufacture of automotive and aerospace components. Melt treatment of the in-situ composite with the addition of Ce has resulted in a change in the primary and eutectic Mg2Si phases to refined morphology, which would be expected to improve the mechanical properties of the composite. Characteristic parameters of Mg2Si particles have been investigated via thermal and microstructural analysis. This has revealed that the addition of 0.8wt.% Ce produced optimum refinement effects on Mg2SiP because the coarse structure has been changed to a polygonal shape and reduced in size. Similarly, the flake-like morphology of Mg2SiE has been transformed into a rod-like or fibre form in addition to reduction of the eutectic cell area. The result also showed an increase in nucleation temperature TN of Mg2SiP while depressed for Mg2SiE, which also corresponds to the refinement morphology effect.

Al-Mg2Si in-situ composite have received wider attention due to their improved properties which mark them as attractive candidate to manufacture most of automotive and aerospace components. Result show that the melt treatment of the in-situ composite by addition of antimony caused to refining the morphology of primary Mg2Si reinforcement which would expect to improve the mechanical properties. Effect of Sb on the characteristics parameters of Mg2Si particles have been investigated by thermal and microstructural analysis. The result has revealed that addition of 0.8 wt.% Sb produced optimum refinement effect on the morphology as coarse structure has been changed to polygon one. The result also showed depression with nucleation temperature, TN and growth temperature, TG which also correspond to the refinement effect.

Al-Mg2Si in-situ composite as a class of advanced engineering materials has possessed better properties which enhanced them to be potential candidate to manufacture most of automotive and aerospace components. Melt treatment of the in-situ composite by addition of bismuth, Bi has resulted in a change of primary Mg2Si reinforcement to a refined morphology which would expect to improve mechanical properties of the composite. Characteristics parameters of Mg2Si particles have been investigated via thermal and microstructural analysis. It has revealed that 0.4wt.% Bi addition produced optimum refinement effect on the morphology since coarse structure has been change to polygon one and reduced most in size. The result also showed depression in nucleation temperature, TN and growth temperature, TG which also correspond to the refinement effect.

•Attenuator acts as a safety device during vehicle structure experiences impact loading or crash accident.•Waste resources, e.g., waste can is considered as an attenuator material as an effort of sustainable recycling.•Nonlinear finite element (NLFE) algorithm is used to idealize impact on the attenuator.•The attenuators with can thickness 1 mm are recorded to have internal energy 16,782.6J for the A2 and 16,380.3J for A4.•Energy capacity of the newly designed attenuator satisfyingly surpasses the FSAE Rules series 2019.