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Cu additions notably strengthen Al-Mg-Si and Al-Si-Mg alloys due to the dense precipitation of quaternary nano precipitates during ageing. However, the chemical evolution and mechanical behaviors of the quaternary micro-scale Q constituent phase occurring in cast and homogenized states have rarely been studied. Meanwhile, there exists a type of AlCuMgSi cluster in the cast state, which has been regarded as Q particles. The accurate identification of phase constituents is the basis for the future design of alloys with better performance. In our work, this type of cluster was revealed to consist of α-Al, θ-Al2Cu, Q, and Si phases through micro-to-atomic scale studies using scanning and transmission electron microscopes. The skeleton of the dendrite was θ phase. The second phases in the dendritic eutectic cluster dissolved quickly during a 4 h homogenization at 550 °C. The Q phase was found to effectively absorb the Fe impurities during casting and homogenization. As a result, the formation of other harmful Fe-rich intermetallics was suppressed. These Q constituent particles were observed to break into separate pieces in an intermediately brittle manner when compressed in situ in a scanning electron microscope. These findings provide insights into the thermodynamic modeling of the Al-Mg-Si-Cu system and alloy design. [ABSTRACT FROM AUTHOR]

Soft materials such as silver, copper and Babbitt SnSb11Cu6 were deposited on the surface of tin bronze by electro spark alloying (ESA) to form the antifriction coating. The data of the antifriction coating were tested by electronic balance, three-dimensional optical profilometer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Xray diffractometer (XRD), Vickers microhardness tester and tribometer. The mass gain, roughness, thickness, surface morphology and phase composition, cross-section and element distribution, microhardness and tribological properties of the antifriction coating were analyzed. The results show that the grain size of the antifriction coating is fine and the metallurgical bonding between the coating and the substrate is good. The surface of each substrate is composed of three layers of coating. The optimal parameters of electro spark alloying are as follows: the discharge voltages of Ag, Cu and Babbitt alloy coatings are 60 V, 60 V and 30 V respectively, the energy storage capacitance is 150 μF, 150 μF and 90 μF respectively, and the working efficiency is 3 min/cm², 3 min/cm² and 4 min/cm² respectively. Under the optimized parameters, the average mass transfer efficiency is 54.4 mg/cm², the average surface roughness is 32.3 μm, and the maximum thickness is about 160 μm. The surface friction coefficient of the soft antifriction coating is 55.6 % of that of the tin bronze substrate. The main wear mechanisms of the soft antifriction coating prepared by electro spark alloying technique are plastic deformation accompanied by slight polishing. [ABSTRACT FROM AUTHOR]

Device-related infection or inflammatory and stress shield are still the main problems faced by titanium alloy implants for long-term implantation application; therefore, it is of great significance to design an alloy with low elastic modulus and good antibacterial properties as well as good biocompatibility. In this paper, Ti-13Nb-13Zr-xCu(x = 3, 7 wt.%) alloys were designed and prepared to reveal the influence of Cu content on the elastic modulus and antibacterial property. X-ray diffractometer, metallographic microscope, scanning electron microscope, and transmission electron microscope were used to study the phase transformation, microstructure, mechanical properties, antibacterial properties, and cytotoxicity of the alloys. The experimental results have demonstrated that the antibacterial performance and the elastic modulus were significantly improved but the corrosion resistance deteriorated with the increase of the copper content. Ti-13Nb-13Zr-3Cu with a low modulus of 73 GPa and an antibacterial rate of over 90% against Staphylococcus aureus (S. aureus) exhibited great potential as a candidate for implant titanium in the future. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition, precipitates evaluation, casting, and mechanical properties of the novel cast Al-4Cu-2.1Er-1Mg-0.2Zr-0.2Cr-0.15Fe-0.15Si-0.1Ti alloy were analyzed using by optical microscope, scanning and transmission electron microscopes, differential scanning calorimetry, thermodynamic calculations, hot cracking and mechanical properties measurements. The positive effect of Cr as a substitution of Mn on plasticity and precipitation strengthening was demonstrated. The 0.2Zr, 0.2Cr and 0.1 Ti as a grain refiners provide a fine grain size of 25 μm in the as-cast state due to primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles formation as a nucleation centers of Al. The hot cracking index (HCI) of the AlCuErMgCr alloy was 12–14 mm which is similar with HCI of the cast Al-Si-Cu-Mg alloys. The good casting properties in the AlCuErMgCr alloy achieved due to a fine grain structure and narrow solidification range. The contribution of the Al 3 (Zr,Er) (40 nm), Al 45 Cr 7 (6 nm), and S'(θ') (100/5 nm) precipitates is 38.5 MPa, 140.4 MPa, and 198.9 MPa and the calculated contribution from dislocation and precipitates is 262.3 MPa. The ultimate tensile strength (UTS) and elongation (El.) of the AlCuErMgCr alloy are 372 MPa and 6% which is higher in 16.6% and 150%, respectively, than in the Mn-containing alloy. Novel alloy has an excellent combination of yield strength (YS) and plasticity at 20–250°C. The YS and El. are 301 MPa and 6% and 225–250 MPa and 4.6–11.5% at 20 and 200–250°C, respectively. The rupture strength at 250°C after 100 h (σ 100 250) is 106 MPa. Mechanical and casting properties of the novel alloy are superior to the properties of commercial 201.0 (Al-Cu-Mn-Mg-Ag-Ti) alloy. • Cr, replacing Mn, had a positive impact on both plasticity and precipitation strengthening. • 0.2Zr, 0.2Cr, and 0.1Ti as grain refiners resulted in the formation of primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles. • The AlCuErMgCr alloy displayed an ultimate tensile strength (UTS) of 372 MPa and an elongation (El.) of 6%. • The rupture strength at 250°C after 100 hours was determined to be 106 MPa. [ABSTRACT FROM AUTHOR]

This paper reports a study on four historical samples from 19th century originating from Croatia, Europe, made of silver plated and gilded copper alloys. The investigation was carried out by chromatographic, spectroscopic, and microscopic techniques. Corrosion was identified in all samples by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), although the samples were in well-preserved states. EDS has given the following average composition of elements Ag (82.99, 4.74, 6.34, and 15.54 wt% in samples 1-4, respectively), Au (17.01 wt% in sample 1), and Cu (0, 95.26, 93.66, and 84.46 wt% in samples 1-4, respectively) for the outer layers of the samples. The exact sample elemental composition was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES): 0.12, 0.22, 0.68, and 1.20 wt% Ag in samples 1-4, respectively and 0.02 wt% Au in sample 2, all on Cu alloys with impurities of Fe, Mn, Ni, Pb, Sb, Si, Sn, and Zn (in quantities 0.05-1.48 wt%). Preliminary detection of metals was performed by thin-layer chromatography. Results of determined chemical composition were consistent with similar investigations, since silver-plated and gilded Cu alloys were the materials used in the production of similar samples through the history. [ABSTRACT FROM AUTHOR]

The as-cast QT700-6 alloy was synthesized with addition of a certain amount of copper, nickel, niobium and stannum elements by alloying method in a medium frequency induction furnace, aiming at improving its strength and toughness. Microstructures of the as-cast QT700-6 alloy were observed using a scanning electron microscope (SEM) and the mechanical properties were investigated using a universal tensile test machine. Results indicate that the ratio of pearlite/ferrite is about 9:1 and the graphite size is less than 40 μm in diameter in the as-cast QT700-6 alloy. The predominant refinement mechanism is attributed to the formation of niobium carbides, which increases the heterogeneous nucleus and hinders the growth of graphite. Meanwhile, niobium carbides also exist around the grain boundaries, which improve the strength of the ductile iron. The tensile strength and elongation of the as-cast QT700-6 alloy reach over 700 MPa and 6%, respectively, when the addition amount of niobium is 0.8%. The addition of copper and nickel elements contributed to the decrease of eutectoid transformation temperature, resulting in the decrease of pearlite lamellar spacing (about 248 nm), which is also beneficial to enhancing the tensile strength. The main fracture mechanism is cleavage fracture with the appearance of a small amount of dimples. [ABSTRACT FROM AUTHOR]

In this study, we systematically investigated several typical interfaces of the T-phase (a precipitated phase in 2024 alloy), namely the T(200)/Al(403), T(101)/Al( 4 ‾ 03) and T(200)/Al(301) interface and analyzed interface properties through first-principles calculations and HAADF-STEM (High-angle annular dark-field scanning transmission electron microscope) observations. The calculation results show that AlMn- terminated interface is the most thermodynamically stable of the different terminal interfaces in T(200)/Al(403) and T(101)/Al( 4 ‾ 03) interface. Therefore, we also speculate that the T precipitated phase forms interface with aluminum matrix through the AlMn- terminated. By investigating the DOS(density of states) and the electron density difference of the interface, we prove that Al–Mn covalent bond is formed on the outer surface of the T phase. In addition, this work provides some basis for the analysis of the T phase and T/Al interface from an energy point of view through various data, which helps us to further investigate the properties of the interface. • Characterization of T(Al 20 Cu 2 Mn 3) precipitated phases in 2024 aluminum matrix by HAADF-STEM and EDS mapping. • For the first time and systematically, first-principle calculations were performed for different interfaces of T-phase, and their various properties were analyzed. • Three different interface calculations show that the AlMn- terminated interface is the most thermodynamically stable. • The (101) T / / (4 ‾ 03) A l interface is more stable. [ABSTRACT FROM AUTHOR]

• The effects of Cu or Zn on the fluidity of A357 alloy were investigated. • With increase of Cu or Zn content, the fluidity of A357 alloy decreased. • With increase of Cu or Zn, the solidification temperature range increased. • The coarse grain is not the main reason for the fluidity to deteriorate. Excellent fluidity is an essential condition for Al-Si-Mg alloy (like A357) to make large thin-walled and complex structure castings, but t here is no research about the effects of Cu or Zn on the fluidity of Al-Si-Mg alloys. Under sand casting conditions, the effects of Cu or Zn on the fluidity of A357 were investigated through spiral fluidity resin sand molds, DSC, polarizing microscope and SEM. The results showed that with increase of Cu or Zn content, the solidification temperature range (T) of A357 alloy increased, and the fluidity decreased. With Cu or Zn addition, the grain size of A357 alloy increased, but the coarse grain is not the main reason for the fluidity to deteriorate. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (HEA) are promising materials for high temperature applications. This work presents investigations of the room temperature tensile mechanical properties of selected 3 and 4 elements medium entropy alloys (MEA) derived from the HfNbTaTiZr system. Tensile testing was combined with fractographic and microstructure analysis, using scanning electron microscope (SEM), wavelength dispersive spectroscope (WDS) and X-Ray powder diffraction (XRD). The 5 element HEA alloy HfNbTaTiZr exhibits the best combination of strength and elongation while 4 and 3 element MEAs have lower strength. Some of them are ductile, some of them brittle, depending on microstructure. Simultaneous presence of Ta and Zr in the alloy resulted in a significant reduction of ductility caused by reduction of the BCC phase content. Precipitation of Ta rich particles on grain boundaries reduces further the maximum elongation to failure down to zero values. [ABSTRACT FROM AUTHOR]