Strain rate sensitivity of the aluminium-magnesium-scandium alloy - Scalmalloy®

This work investigates the strain rate sensitivity of the aluminiummagnesium-scandium alloy Scalmalloy, which is used extensively for additive manufacturing of lightweight structures. This high strength aluminium alloy combines very good weldability, machinability and mechanical strength: it can be heat-treated to reach nominal ultimate tensile strengths in excess of 500 MPa. We report tensile tests at strain rates ranging from 10−3 /s to 103 /s at room temperature. It is well known that Al-Mg alloys exhibit a negative strain rate dependency in combination with serrated flow caused by the Portevin-Le Chatelier effect, which describes the interaction of Mg solutes with dislocation propagations. In contrast, in Al-Sc alloys, the flow stress increases with increasing strain rate and displays positive strain rate dependency. Additionally, the presence of Sc in the form of Al3-Sc provides a fine-grained microstructure which allows higher tensile and fatigue strength. This research shows how these combined effects interact in the case of Scalmalloy, which contains both Mg and Sc. Tests are performed at quasi-static, intermediate and high strain rates with a servohydraulic testing machine and a Split-Hopkinson tension bar. Local specimen strain was performed using 2D Digital Image Correlation.

Quantum chemical calculations of thermodynamic and mechanical properties of the intermetallic phases in copper–scandium alloy

To understand how the intermetallic phases of Cu–Sc influence the thermal stability and mechanical strength of Cu–Sc alloys, thermodynamic and mechanical characters of the Cu–Sc alloy have been calculated by first-principles. The lattice parameters of Cu4Sc phase are obtained by calculated and the CuSc phase is found to be the most stable phase based on formation energies. In the binary Cu–Sc alloy, the shear moduli of Cu4Sc and Cu2Sc phases along the [100](001) crystal orientation are easier than those along the [100](010) crystal orientation, respectively. Pure Cu phase acts as the most stiffness phase while [Formula: see text]Sc phase has the lowest stiffness. Cu4Sc phase possesses the best plasticity while CuSc phase possesses the worst plasticity. Cu4Sc phase is the most ductile phase while [Formula: see text]Sc phase is the most brittle phase. From the partial density of states, the valence bands of binary Cu–Sc phases are dominated by the Sc-[Formula: see text] states.

Influence of Scandium on Magnesium and its Structure-Property Correlation

Magnesium alloys are the most demanded lightweight structural materials for different engineering applications such as aerospace, automobile, electronics, etc. However, the high temperature properties of Mg alloys are not comparable with its competitor, the Al alloys. Mg alloys are not recommended beyond 120°C due to their poor creep and oxidation resistance. In order to improve the high temperature properties of the magnesium alloys, rare earth containing Mg alloys were developed. Among these alloys, Mg-Sc alloys were found to be very interesting which exhibits better high temperature properties. In the present work, magnesium-scandium alloy was fabricated through liquid metallurgy route under inert cover. The alloy was characterized by optical microscopy, X-Ray Diffraction (XRD), Differential Thermal Analysis (DTA) and hardness testing. The microstructural analysis reveals the α-Mg phase and the distribution of fine Mg-Sc intermetallic. It is observed from the DTA that the melting point of the base alloy has got enhanced by the addition of Sc. There is also an appreciable improvement in the hardness by the addition of Sc.