[en] Pd_77.5Cu₆Si_16.5 (at.%) bulk metallic glass with a diameter up to 11 mm was successfully fabricated by water quenching method together with melt purification. By using x-ray diffraction and transmission electron microscopy techniques, the structure of the as-prepared sample is confirmed to be glassy. The resulted sample with 11 mm diameter indicates that the melt purification by fluxing method can effectively enhance the glass forming ability of Pd-Cu-Si alloy, and increase its critical size of glassy sample. (condensed matter: structure, mechanical and thermal properties)

[en] We prepare Pd_40.5Ni_40.5P₁₉ glassy samples with purified ingots by copper mold casting at a high cooling rate and by water quenching at a low cooling rate. Both of them exhibit different supercooled liquid regions and multiple glass transition characteristics in their differential scanning calorimetric curves. The plasticity of the glassy sample prepared by copper mold casting is about 5% while that prepared by water quenching is almost zero (0.2%), indicating that cooling rate has influenced the plasticity of glassy alloys. By using high resolution TEM image analysis, it is revealed that there exist characteristic regions with different contrasts in the full glassy samples. The characteristic size is about 20–40 nm for the glassy sample prepared by water quenching and 2–4 nm for the one prepared by copper mold casting. The large difference in the plasticity of the glassy samples prepared by different cooling rates is believed to be related to the difference in the size of the characteristic nanoscale structures. The results indicate that adjusting cooling rate in preparation of glassy samples could modify the thermal and mechanical properties of the glassy alloys. (condensed matter: structure, mechanical and thermal properties)

[en] Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe_8_1P_8_._5C_5_._5B_2Si_3 BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe_8_2Mo_1P_6_._5C_5_._5B_2Si_3 BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications. - Highlights: • Novel Fe-based BAA with no other metallic element except 81 at% Fe was prepared. • Fe-based bulk amorphous alloy (BAA) with the highest Fe content (82%) was prepared. • Very high saturation magnetization of 1.59 T has been achieved. • A new thought for designing Fe-based BAA with high Fe content was provided

[en] Effects of Ti addition on the microstructures and mechanical properties of AlCrFeNiMo _0.5 Ti _x ( x=0, 0.25, 0.4, 0.5, 0.6, 0.75) high entropy alloys (HEAs) are investigated. All these HEAs of various Ti contents possess dual BCC structures, indicating that Ti addition does not induce the formation of any new phase in these alloys. As Ti addition x varies from 0 to 0.75, the Vickers hardness (HV) of the alloy system increases from 623.7 HV to 766.2 HV, whereas the compressive yield stress firstly increases and then decreases with increasing x above 0.5. Meanwhile, the compressive ductility of the alloy system decreases with Ti addition. The AlCrFeNiMo _0.5 Ti _0.6 and AlCrFeNiMo _0.5 Ti _0.75 HEAs become brittle and fracture with very limited plasticity. In the AlCrFeNiMo _0.5 Ti _x HEAs, the AlCrFeNiMo _0.5 HEA possesses the highest compressive fracture strength of 4027 MPa and the largest compressive plastic strain of 27.9%, while the AlCrFeNiMo _0.5 Ti _0.5 HEA has the highest compressive yield strength of 2229 MPa and a compressive plastic strain of 10.1%. The combination of high strength and large plasticity of the AlCrFeNiMo _0.5 Ti _x ( x = 0, 0.25, 0.4, 0.5) HEAs demonstrates that this alloy system is very promising for engineering applications. (paper)

[en] Highlights: • Passive films were separated from glassy substrates as large-area thin membranes. • The highly homogeneous passive films exhibited a single-layer amorphous structure. • Main components of the passive films for the Ti-based MGs were TiO₂, ZrO₂ and BeO. • Alloying Fe and Ni contributed to the enrichment of TiO₂ in the passive film. • Addition of Ni facilitated to improve the structural compactness of passive film. Resolving structural and componential characteristics of passive film is a long-standing challenge in corrosion science since it’s difficult to separate extremely thin passive films. In this work, the passive films are successfully separated from Ti-Zr-Be-Al/Ni/Fe glassy substrates as large-area thin membranes by the designed “Ribbon-Penetration” method. The homogeneous and continuous passive films are identified as a single-layer amorphous structure, whose primary components are TiO₂, ZrO₂ and BeO. Alloying Ni or Fe element could induce the enrichment of TiO₂ in the passive films and improve the structural compactness, resulting in the superior corrosion resistance in 3.5 wt.% NaCl solution.

[en] Highlights: • The glass-forming ability and critical size of amorphous for the fluxed Fe₆₆Co₁₅Mo₁P_7.5C_5.5B₂Si₃ alloy is 2 times that of the non-fluxed alloy. • The fluxing treatment bulk amorphous alloy also exhibits better thermal stability and ductility than those prepared by no-fluxing treatment. • Fluxing treatments can be effective elimination of the impurities within the alloy. - Abstract: The effect of fluxing treatment on the properties of Fe₆₆Co₁₅Mo₁P_7.5C_5.5B₂Si₃bulk amorphous alloy (BAA) has been investigated. Prepared by a combination method of flux treatment and water quenching, the Fe₆₆Co₁₅Mo₁P_7.5C_5.5B₂Si₃ BAA exhibits better glass-forming ability, thermal stability, soft magnetic properties and ductility than those of the one prepared by direct water quenching. This indicates that fluxing treatment can play a potential role in improving the properties of Fe-based BAA due to the effective elimination of the impurities within the alloy.

[en] Highlights: • Nanoporous Cu&Ag@Ag alloy was prepared by dealloying Zr–Cu–Ag–Al–O ribbon. • Oxygen introduction can tune the dealloying morphology by enabling the dissolution of Cu. • The nanoporous Cu&Ag@Ag alloy exhibits enhanced and robust antibacterial activity. Metallic glasses are perfect materials for preparing nanostructures by dealloying, but the obtained nanostructures are commonly of porous structures. Through the combination of chemical dealloying and ultrasonic vibration, ultrathin Cu&Ag bimetallic nanoporous membranes (NPMs) have been prepared from a Zr₄₈Cu₃₆Ag₈Al₈ MG ribbon. Furthermore, by introducing oxygen into the Zr₄₈Cu₃₆Ag₈Al₈ MG ribbon to change the mechanism of the dealloying process, nanoporous (Cu&Ag)@Ag core-shell alloy was synthesized by the one-pot chemical dealloying of Zr–Cu–Ag–Al–O amorphous/crystalline composite, which provides a new way to prepare metallic core–shell nanostructures by a one-pot method. The introducing of oxygen can enable the dissolution and redeposition of Cu, and tunes the Cu&Ag NPM into the nanoporous (Cu&Ag)@Ag core-shell alloy. The nanoporous (Cu&Ag)@Ag core-shell alloy exhibits better and robust antibacterial activity against E. Coli DH5α due to its better oxidation resistance caused by the Ag skin. The present work provides important insights into the tuning of nanostructures through simple dealloying.

[en] Highlights: • Joining of a Ti-based strong glass former using friction stir spot welding process was studied. • Effects of welding parameters on the fracture load and fractured surfaces were analyzed. • Different zones in the weld spot were characterized and stir zone, TMAZ and base metal were identified. • Nano crystal/BMG's composite formation in the stir zone under the tool shoulder was the reason for higher fracture load. • Stir zone under the tool tip and the TMAZ had similar hardness and shear bands pattern with different structural reasons. In this study, TiZrFeBeCu bulk metallic glass plates have been welded together by using the friction stir spot welding method. The effects of processing parameters on the microstructure and mechanical properties of the joints have been studied. It has been found that the plunge depth has a crucial effect on the fracture mode and fracture strength of the joint. Both tool rotation speed and holding time significantly influence the tensile/shear fracture load and the fracture toughness. The correlation between fracture surface and the fracture toughness have been analyzed. The results revealed that there exist three regions in the spot welding of bulk metallic glass plates: stirring zone, thermo mechanically affected zone and base metal. It shows that stirring zone under the tool shoulder and around the tool tip possesses different structures and micro-hardness from that beneath the tool tip. The thermo mechanically affected zone and the stirring zone under the tool tip have similar hardness and structure. Stress relief annealing was used to clarify the reason for the hardness difference at different regions. Changes in the hardness in different areas of the welding spot can be correlated with the shear bands pattern and plastic zone size around the Vickers indents.

[en] Highlights: • Influence of quenching and partitioning process on stainless steel was studied. • Pitting potentials of experimental steel partitioned at 350 and 450 °C were higher. • Retained austenite and M_3C carbides existed in matrix of experimental steel. • Retained austenite is beneficial for the corrosion resistance of stainless steel. - Abstract: A 0.3C–13Cr martensitic stainless steel (MSS) was subjected to quenching and partitioning (Q&P) treatment. Due to the different thermodynamic condition from the standard constrained carbon equilibrium (CCE), both the carbides precipitation and the interface migration occur during the partitioning step in the Q&P treatment. However, a sufficient amount of austenite is still retained in the Q&P treated MSS. After being partitioned at 350 °C and 450 °C, the Q&P treated MSS exhibits better corrosion resistance than the same steel treated via conventional quenching and tempering (Q–T) treatment.