The demand for lighter weight decreased thickness and higher strength has become the focal point in the automotive industry. In order to meet such requirements, the addition of several alloying ...elements has been started to be investigated. In this work, the additions of V, B, and Sr on feedability and tensile properties of A360 has been studied. A mold design that consisted of test bars has been produced. Initially, a simulation was carried out to optimize the runners, filling, and solidification parameters. Following the tests, it was found that V addition revealed the highest UTS but low elongation at fracture, while B addition exhibited visa verse. On the other hand, impact energy was higher with B additions.
With V addition to A360, UTS increases but ductility suffers; By B addition impact properties increased. Display omitted
•Vanadium addition to A360 significantly reduces dendrites in HPDC•Vanadium addition increases tensile properties but becomes brittle•Boron addition increases ductility of A360•Highest impact energy is obtained with boron addition•Strontium modification enhances mechanical properties
With the rapid development of cloud applications, the workload pattern of datacenters presents the characteristics of mixed long and short flows and frequent micro-burst traffic, which puts forward ...new requirements for network transmission performance, including ultra-low latency, high throughput, and strong stability. At the same time, datacenters begin to deploy the low-diameter topology to accommodate these new requirements, and the high-performance datacenter (HPDC) comes into being. However, due to the complexity of the load, existing congestion control mechanisms cannot control dynamic delay in the network well, which significantly restricts the development of the HPDC. Therefore, it is necessary to deploy the congestion control mechanism for the HPDC. So we propose EagerCC, an ultra-low latency, low-overhead, and accurate congestion control mechanism based on In-Network-Telemetry (INT) information for various datacenter scenarios, especially for HPDCs. EagerCC uses switch-feedback, ACK-padding, ACK-first to reduce feedback delay and uses switch-calculation, probabilistic ACK-padding to reduce the overhead of congestion signals. We conduct a lot of experiments and the result shows that EagerCC performs well in various datacenter scenarios, especially for HPDCs. Specifically, EagerCC reduces the 99th-FCT and avg-FCT by 52.3% and 13.3% for the HPC workload NPB-CG compared to HPCC in Dragonfly. In addition, EagerCC significantly reduces the network’s feedback delay and queue occupancy.
AZ91, as one the most popular magnesium alloys is widely employed for various engineering applications in the automotive industry. They are primarily made from high pressure die cast processes (HPDC) ...with different wall stocks, which affect their engineering performance. Understanding the effect of thick wall stocks on mechanical behaviors of HPDC AZ91 is crucial for proper design of lightweight components to meet desired engineering requirement. In this research, a conventional high pressure die casting process was utilized to prepare rectangular specimen of AZ91 with wall thicknesses of 10 mm, 6 mm and 2 mm. Tensile testing, porosity measurement and microstructure analyses were carried out on prepared specimens at room temperature. The mechanical testing evaluation reveals that, as the wall stocks of AZ91 deceases, their tensile properties including yield strength (YS), ultimate tensile strength (UTS) and elongation (ef) increase. The porosity content caused by air entrapment and the dendritic structure due cooling mechanisms should be responsible for the resultant mechanical properties.
For understanding the processing-microstructure-properties correlation of high pressure die casting (HPDC) AZ91D alloy, 3D reconstruction was carried out to characterize the microstructural ...morphologies of castings produced by four designed HPDC processes. The influence of different parameters (vacuum, slow-shot speed, fast-shot speed) on porosity volume and morphology, defect band width and average externally solidified crystals (ESCs) size of castings were systematically studied. Microstructural characterization revealed that the defect band width was strongly related with the size and quantity of ESCs, rather than the porosity volume. Meanwhile, ESCs were mainly influenced by the slow-shot speed in shot sleeve (ESCs growth time) and fast-shot speed into the die cavity (shear stress of melt flow). Tensile fracture revealed that cracks easily propagated within the defect bands due to the accumulated ESCs and connected irregular pores, while the cracks were restrained in center zone. The mechanical properties of HPDC castings was inversely proportional to the defect band width, and is not dependent on the average volume fraction porosity.
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Aimed at the mechanical property improvement in the high pressure die casting (HPDC) process for the aluminium alloy, two sets of shot curves (the baseline and the optimized ...condition) are designed to study their influence on the distributions of the ultimate tensile strength (UTS) and the elongation (El) for the as-cast ASTM tensile samples. Difference in the as-cast microstructures and defects are characterized and compared accordingly. Following the experiments, a mathematical model for the entire HPDC process is established to study the characteristics of the melt flow, heat transfer, solidification and defects formation (entrapped gas, oxides, porosities) during the HPDC process with the two above-mentioned piston shot curves are analyzed. The results have shown that the UTS and the El are improved obviously with the optimized shot profile. And the mechanism for these changes are explained in detail. This work provides a novel approach for designing and optimization of metal casting process without conducting excessive experiments and it could be transferred and applied to various alloys systems and different casting processes.
•Changing Ni content in alloy causes formation of different Ni containing phases.•Formation of Ni containing intermetallics reduce the amount of Al2Cu phase.•Existence Ni bearing intermetallics has a ...dramatical effect properties of material.•Lower Ni additions are desirable for improving the mechanical properties.
Investigations have been carried out to understand the correlation between Ni content and properties of HPDC cast A384 aluminium alloy in as-cast and heat-treated conditions. Depending on Ni content in the alloy, different Ni-bearing intermetallics were formed. Suitable heat treatment conditions were selected after a series of experiments to obtain optimal mechanical properties. Most of the Ni containing intermetallics found to be stable at solutionizing temperatures which have a dramatic effect on the mechanical properties of alloys after natural and artificial aging. The results showed that, after heat treatment, to achieve higher strength values lower Ni additions are favourable.
Commonly the reduction of weight in transport is applied to passenger cars, while commercial vehicles are still not widely involved due to structural and costs restraints. This research studied a new ...concept of aluminium cross beam suspension for commercial vehicles that would replace the currently used steel component. The related advantages entail the achievement of an affordable solution, weight reduction of about 50%, environmental benefits, avoidance of painting and excellent recyclability. The use of appropriate materials, a new concept of design and a careful function integration allowed the structural limits to be overcome. The feasibility of this solution was verified through detailed characterisation and testing, composed of an analysis of the most relevant failure modes, with microstructures, hardness tests, tensile tests, fractography, salt spray test and fatigue test bench road simulator with field test data. The validation was successfully completed and the feasibility of the light alloy use for this particular heavy application was demonstrated. Further experiments, based on the development of heat treatments for potential future extension of this application, were conducted with the support of Design Of Experiment methodology. The outputs constitute a useful database of properties.
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•-50% weight aluminium EN AC-43500 cross beam suspension for CV was developed, overcoming costs and structural limits•Proof of the good resistance to corrosion and of the desired mechanical properties of the cross beam suspension•Confirmation that the cross beam of the independent front suspension can endure 250’000 km road application without fatigue failure•Final demonstration of the feasibility of the light alloy use for this particular heavy application•Database of EN AC-43500 mechanical properties, useful for the for the designing of different automotive components
The thermal stability and grain growth kinetics of a high-pressure die casting (HPDC) Mg-6Y–3Zn-1Al (WZA631, wt%) alloy with long-period stacking ordered (LPSO) phase is studied by subsequent ...annealing at different temperatures and time. The grain size of the as-cast and annealed samples is determined using the linear intercept method. It is found that grain size of WZA631 alloy hardly changes up to 450 °C, indicating the microstructure is thermally stable. The grain growth kinetics of WZA631 alloy between 450 °C and 550 °C is well described by the kinetic equation, Dn−D0n=kt. The grain growth exponent varies with temperature, ranging from n = 4.98 at 450 °C to n = 1.45 at 550 °C. The values of activation energy Eg are approximately 122.5 kJ/mol and 139.1 kJ/mol, respectively, for annealing temperature below and above 500 °C, which identifies the bulk diffusion to be the principal grain growth mechanism in the studied temperature range. The growth rate constant k at 450–500 °C is around 2–4 orders lower than other typical Mg alloys, suggesting the excellent thermal stability below 500 °C. The grain coarsening temperature TGC and softening temperature TS are all around 500 °C, implying the critical temperature related to the thermal stability of WZA631 alloy is ~500 °C. The microstructure evolution shows that LPSO network structure is a predominant factor inhibiting the grain growth of HPDC WZA631 alloy, and the dissolution of LPSO results in the variation of grain growth exponent.
•The microstructure of HPDC WZ631 alloy is thermally stable up to 450 °C.•The grain growth rate constant at 450–500 °C is 2–4 order lower than other Mg alloys.•The continuous network of LPSO structure inhibits the grain growth of WZ631 alloy.
To achieve high power density, increasing the switching frequency of the power converter has become a trend. The LCL filter is a major contributor of the overall weight of a high-power-density ...converter (HPDC), especially the inverter-side inductor, which requires to suppress higher frequency harmonic contents at the inverter side. This paper describes a comprehensive design flow of the LCL filter for a 50-kW, 60-kHz two-level silicon carbide (SiC) inverter for high-power aerospace applications with space constraint and harsh ambient temperature environment. To meet the space constraint requirement and reduce the inductor size, specific design attention is made on a customized amorphous cored inductor with a comprehensive study on the relationships of inductor weight, core width, and total surface area with respect to air gap length. To overcome the harsh ambient temperature environment, a liquid cooling system of the amorphous cored inductor is also described.
Porosity is one of the challenges in high-pressure die casting (HPDC) of aluminum alloys. A typical control of porosity involved controlled solidification which is attained by the cooling of the die. ...In traditional cooling, this is done by straight cooling channels. However, they can be ineffective due to the limited geometry of these channels. Alternatively, conformal cooling channels can be produced in any geometry by additive manufacturing. In this study, the thermal analysis of the mass production engine crankcase die was performed and the regions where the metal-die heat transfer load is high and limiting the production rate were examined. In order to increase the heat transfer and maximize the cooling rate in the different locations of the mold, conformal cooling inserts were designed and produced in a direct metal laser sintering 3D print machine by additive manufacturing technology. AlSi9Cu3 alloy was used to produce the cast part by HPDC. It was observed that porosity was decreased by 43% (from 251 to 156 mm
3
) and the cycle duration was decreased by 4 s when conformal cooling was used. Secondary dendrite arm spacing (SDAS) was decreased by 39% to 8.27 mm while eutectic silicon modification was enhanced.
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