W. Kasprzak

Dislocation slip distance during compression of Al–Si–Cu–Mg alloy with additions of Ti–Zr–V

Abstract The plastic deformation behaviour of the Al–Si–Cu–Mg alloy with micro-additions of Zr–V–Ti was measured in the temperature range of 298–673 K and the true stress–true strain compression curves were used to calculate the dislocation slip distance (DSD). A new constitutive equation for the temperature dependent DSD was developed, based on Mott’s theory of strain hardening. The DSD predicted by the model was in good agreement not only with values achieved for the Al–Si–Cu–Mg alloy tested but also for other Al based and Pb–Sb alloys with deformation data available in the literature. A comparison of deformation and microstructure suggests that the grain refinement during hot compression deformation occurring due to continuous dynamic recrystallisation is responsible for a drastic growth of the DSD.

Aging characteristics of the Al-Si-Cu-Mg cast alloy modified with transition metals Zr, V and Ti

The hypoeutectic Al-7Si-1Cu-0.5Mg base alloy was modified with different contents of Zr, V and Ti. The wedge-shape samples with varying solidification rates during casting were subjected to isochronal aging at temperatures up to 500 °C. Moreover, as-cast and solution treated alloys were subjected to long-term isothermal aging at 150°C. As a reference, the A380 alloy, seen as commercial standard for the automotive application target, was used. The modified alloys exerted different aging characteristics than the A380 grade with higher peak hardness and lower temperature of alloy softening. Besides, the influence of the applied solidification rates on hardness after aging was less pronounced in modified alloys than in the A380 grade. For three combinations of Zr, V and Ti tested with contents of individual elements ranging from 0.14 to 0.47%, no essential differences in aging characteristics were recorded. The results are discussed in terms of the role of chemistry and heat treatment in generating precipitates contributing to the thermal stability of Al based alloys.

Heat Treatment of Magnesium Alloys – Current Capabilities

The essential factors controlling current heat treatment of cast and wrought magnesium alloys are reviewed along with the role of chemical composition and specific elements. The strengthening mechanisms and key precipitates are described, explaining crystallographic limitations of their role within the hcp magnesium matrix. Examples of changing properties are given for conventional alloys with trends in alloy design to magnify the aging effect. Emphasis is placed on magnesium structures produced by semisolid processing routes where a new approach to heat treatment is required.

High Temperature Creep Evolution in Al-Si Alloys Developed for Automotive Powertrain Applications: A Neutron In-Situ Study on hkl-Plane Creep Response

Recent trend in the automotive industry towards lightweighting and downsizing the powertrain components, without compromising the power output, have led to increased engine power density. Increased power density frequently requires these lighter components to operate in conditions of increased temperature and pressure, which is challenging for many aluminum alloys in use today in the powertrain manufacturing. Meeting the challenge requires not only improving high-temperature performance of known alloys or developing new ones, but also developing new advanced techniques to understand the long-term behaviour of the alloys.

Effect of Strain Level on the Behavior of Intermetallics and Texture of Al-Si-Cu-Mg Alloy Modified with Transition Metals

T uniaxial compression test was used to assess an influence of strain amount on the behavior of precipitates and texture of the Al-7%Si-1%Cu-0.5%Mg alloy, modified with micro-additions of V, Zr and Ti in as-cast and T6 heat treated conditions. As revealed through metallographic examinations, fracturing and re-orientation of the second phase particles increased with increasing compression strain. For both conditions of the alloy, the intermetallic particles experienced substantially more frequent cracking than the eutectic silicon. At the same time, the precipitates in the T6 heat treated alloy were also more resistant to rotate within the alloy matrix as a result of nano-size Al3X (X=Zr, Ti, & V) secondary precipitates. The crystallographic texture was measured and correlated with deformation behavior of the alloy. The weak texture of {011} and {111} , {112} and {111} components. The intensity of the components differed depending on the strain amount and the state of precipitation where the T6 heat treated alloy always exhibited lower intensity all over the strain. It is concluded that the texture formation in studied alloy is controlled by precipitates formed during T6 heat treatment.

Thermal Stability of Al-Si-Cu-Mg Cast Alloys Modified with Transition Metals Zr, V and Ti

The hypoeutectic Al-7Si-1Cu-0.5Mg (wt%) alloy was modified with micro-additions of Zr, V and Ti in order to improve its thermal stability. As revealed by a number of experimental techniques, Cu and Mg rich phases along with the eutectic Si dissolved in the temperature range from 300 to 500°C. At the same time, the (AlSi)x(TiVZr) phases containing transition metals were present up to 696–705°C. During isochronal aging, the modified alloy exerted different aging characteristics than the reference A380 grade with a higher peak hardness and a lower temperature of alloy softening. Micro-additions of Ti, V and Zr positively affected the alloy strength during testing both in as-cast state and after T6 heat treatment. Improvements in tensile and compressive strength as compared to the reference alloy were preserved up to temperatures over 200 °C with more positive effect seen for the T6 state.

Production of Lithium-Ion Cathode Material for Automotive Batteries Using Melting Casting Process

In the 1990s, LiFePO4 (LFP) was discovered as a cathode material for lithium ion batteries and was successfully used in the variety of devices such as power tools, E-bikes and grid accumulators. New challenges associated with use of lithium ion batteries for automotive applications demand higher performance and operating requirements, yet these requirements need to be achieved at affordable cost and without compromising vehicle safety. The advantages of LFP as a cathode material include thermal stability, limited environmental impact and potential of low cost as compared to the cathode chemistries containing cobalt. Currently, solid state and hydrothermal processes are used to synthesize LFP at the industrial scale. However, they require multiple, time-consuming steps and costly precursors. Recently, a melting-casting process to produce LFP cathode material was investigated. The motivation behind this new process is the great flexibility of raw materials including chemical makeup and particle size, and the use of lower cost, commodity chemicals, with the benefits of increased kinetics in the molten state and energy efficiencies leading to overall process cost savings. Also, if successful this process could represent a novel application of conventional casting. Melting lithium-, iron- and phosphorus-bearing precursors in near stoichiometric ratios and casting LFP material that forms around 1000 °C requires fewer processing steps and shorter reaction time. Initially, electric resistance furnaces were utilized to melt the precursors to synthesize LFP. In this investigation, induction furnace was utilized to significantly reduce the melting cycle time. Various precursors and process parameters were tested from small laboratory samples of less than 1 kg to pilot-scale casting of approximately 40 kg. Cast LFP samples were evaluated using SEM/EDX microscope, differential scanning calorimetry, thermal analysis, X-ray diffraction and battery assemblies in coin cells, and compared against commercial LFP product.

Effect of Transition Metals on Thermal Stability of Al‒Si Cast Alloys

Micro-additions of the transition metals Ti, Zr and V were explored to improve thermal stability of the cast hypoeutectic Al‒7Si‒1Cu‒0.5Mg (wt%) alloy. During high temperature exposures, the Cu- and Mg-rich phases along with the eutectic Si dissolved in the temperature range from 300 to 500 °C whereas the (AlSi)x(TiVZr) phases, containing transition metals, were present until alloy melting. Micro‒additions of Ti, V and Zr increased the alloy strength during testing under both static and cyclic loads. Improvements in the tensile and compressive strength as compared to the reference alloy were observed up to temperatures over 200 °C with more positive effect seen for the T6 state.

Neutron Diffraction Analysis of Phase Precipitation in Solidification of Hypereutectic Al-Si Alloys with the Addition of Cu and Mg

A good understanding of the kinetics of evolution of solid phases during solidification of hypereutectic aluminum alloys is a key factor in controlling the as-cast microstructure and, in turn, enhancing the service properties of industrial alloys.

Microstructure Development and Control in Hypereutectic Cast Al-Si Alloys Evaluated by Metallurgical Analysis and Neutron Diffraction

Presented results show individual effect of key alloying elements, i.e., 2.8%Cu, 0.7%Mg and 0.01%P on the as-cast microstructure development in the hypereutectic Al-19%Si alloy evaluated using classical metallurgical analysis as well as in-situ neutron diffraction during alloy solidification process. Neutron diffraction revealed possible Si atoms clustering above liquidus temperature i.e., 677 °C and pre-mature nucleation of α-Al crystallites below liquidus temperature i.e., 667 and 625 °C in addition to liquid-to-solid phase transformation assessment during solidification. Mechanical strength i.e., hardness and ultimate tensile strength improvement due to Cu, Mg and P additions is evidenced and linked with microstructure evolution under non-equilibrium solidification conditions. Primary Si refinement was improved with subsequent addition of Cu and Mg, and P addition alone had insignificant effect on primary Si refinement.