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Element W can effectively improve the density of energetic structural materials. However, W is an inert element and does not combust in air. To change the reaction characteristics of W, 60 at.% Al was introduced into W through mechanical alloying. XRD analysis shows that after 50 h of ball milling, the diffraction peak of Al completely disappears and W(Al60) super-saturated solid solution powder is obtained. Further observation by HAADF and HRTEM reveals that the W(Al60) super-saturated solid solution powder is a mixture of solid solution and amorphous phase. Based on the good thermal stability of W(Al60) alloy powder below 1000 °C, W(Al60)–Al composite was synthesized by hot pressing process. Impact initiation experiments suggest that the W(Al60)–Al composite has excellent reaction characteristics, and multiple types of tungsten oxides are detected in the reaction products, showing that the modified W is combustible in air. Due to the combustion of tungsten, the energy release rate of the W(Al60)–Al composite at speed of 1362 m/s reaches 2.71 kJ/g.

In this work, a high strength Al alloy was successfully processed via in-situ alloying of AlSi10Mg and Cu elemental powders during Laser Powder Bed Fusion. To get superior strength, 4 wt% of Cu was added to AlSi10Mg composition to benefit from the additional solid solution and precipitation strengthening mechanisms induced by Cu atoms. Microstructure, chemical composition, hardness, and tensile properties of as-built samples were firstly determined. The microstructure showed a dual eutectic formed by Si precipitates intermixed with θ-Al2Cu phase. The average Cu concentration was 3.96 ± 0.26 wt% in line with the theoretical one. Hardness and yield strength of AlSi10Mg + 4Cu alloy showed an increase of respectively 8.8 % and 35.6 % compared to the as-built AlSi10Mg, owing to the highly super-saturated solid solution of Si and Cu atoms upon rapid solidification. After that, a direct aging heat-treatment strategy was pursued to fully exploit the potential alloy precipitation by heating as-built samples at temperatures between 160 and 190 °C. A maximum hardness response was achieved after 1 h at 175 °C. The high hardening was primarily attributed to a mix of θ''/θ'+θ-Al2Cu and Si phases coupled with a still high solid solution content. Nevertheless, direct aging slightly decreased the alloy ductility due to the prominent precipitation of brittle Si particles during aging and the presence of Cu inhomogeneities formed after in-situ alloying.

In this paper, W-33.3 at% Zr super-saturated solid solution powder was prepared by mechanical alloying, and its formation mechanism and thermal stability were systematically studied. After 30 h of milling, 33.3 at% of Zr was completely dissolved in W, and a super-saturated solid solution with BCC structure was formed. When the milling duration was increased to 50 h, the single BCC phase was transformed into a dual-phase mixture with a super-saturated solid solution and an amorphous phase. Thermodynamic calculations based on Miedema theoretical model suggested that the W-33.3 at% Zr binary system tended to form solid solution first and then transform into amorphous. Furthermore, high resolution transmission electron microscopy observation revealed that grain refinement, lattice distortion and dislocation may play an important role in the process of solid solution expansion and amorphization. Finally, thermal stability tests suggested that the prepared super-saturated solid solution powder has shown good stability at 800 ℃ for 2 h, which provides more possibilities for the application of W-Zr metastable alloy powders. [Display omitted] • W-33.3 at% Zr super-saturated solid solution was prepared by mechanical alloying firstly. • W-Zr super-saturated solid solution powder is completely stable after holding at 800 ℃ for 2 h. • Phase evolution of W-Zr binary system was studied by thermodynamic calculation. [ABSTRACT FROM AUTHOR]

Mechanical alloying (MA) of elemental iron, graphite and manganese powders consisting of Fe–7 mass% C–6 mass% Mn were carried out by using a planetary ball mill at different milling speed. The structural evolution of the MAed powders was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The MAed powders were hot isostatic pressed (HIPed) at 100 MPa for 1 h at lower (853 K) or higher (1053 K) than the eutectoid transformation temperature A1. The processes of amorphization, super-saturated solid solution and particle refinement are influenced by the milling speed. These processes are faster with the increase in the milling speed. The hardness and microstructure of the HIPed compacts are influenced by the morphology of the MAed powders obtained. The powders MAed at high speed has higher hardness at the HIPed compacts than the powders MAed at low speed. Since the sintering progresses well at a temperature higher than A1 and the phase transformation of γ-Fe into fine carbide and α-Fe occurs during cooling process, the hardness of the compacts HIPed at 1053 K higher than A1 is greater than that at 853 K lower than A1. [Copyright &y& Elsevier]

[Display omitted] • AlSi10Mg + 4Cu alloy is succesfully processed by laser powder bed fusion in-situ alloying. • Solid solution and precipitation strenghenting mechanisms are exploited for improving AlSi10Mg mechanical properties. • Cu addition increased AlSi10Mg hardness and yield strength of 8.8% and 35.6%, respectively. • Direct aging strategy is pursued to foster the alloy precipitation potential after rapid cooling. • The maximum hardness response is attained after 1 h at 175 °C. In this work, a high strength Al alloy was successfully processed via in-situ alloying of AlSi10Mg and Cu elemental powders during Laser Powder Bed Fusion. To get superior strength, 4 wt% of Cu was added to AlSi10Mg composition to benefit from the additional solid solution and precipitation strengthening mechanisms induced by Cu atoms. Microstructure, chemical composition, hardness, and tensile properties of as-built samples were firstly determined. The microstructure showed a dual eutectic formed by Si precipitates intermixed with θ -Al 2 Cu phase. The average Cu concentration was 3.96 ± 0.26 wt% in line with the theoretical one. Hardness and yield strength of AlSi10Mg + 4Cu alloy showed an increase of respectively 8.8 % and 35.6 % compared to the as-built AlSi10Mg, owing to the highly super-saturated solid solution of Si and Cu atoms upon rapid solidification. After that, a direct aging heat-treatment strategy was pursued to fully exploit the potential alloy precipitation by heating as-built samples at temperatures between 160 and 190 °C. A maximum hardness response was achieved after 1 h at 175 °C. The high hardening was primarily attributed to a mix of θ ' ' / θ ' + θ -Al 2 Cu and Si phases coupled with a still high solid solution content. Nevertheless, direct aging slightly decreased the alloy ductility due to the prominent precipitation of brittle Si particles during aging and the presence of Cu inhomogeneities formed after in-situ alloying. [ABSTRACT FROM AUTHOR]