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Manganese-zinc (MnZn) ferrites have important application in convertors and switching mode power supplies. The core losses ($\text{P}_{L}$) of MnZn ferrites have serious influence on the performance of power conversion devices. It is worth emphasizing that reducing the core losses at high frequency is of great significance for the miniaturization and integration of power conversion devices. Here in this paper, MnZn ferrites have been fabricated by the method of solid-state reaction, and the effect of CaCO3 and V2O5 co-additives on the microstructure and magnetic property has been investigated. This paper illustrated the competition mechanism of grain growth, which originated from the hindrance effect of CaCO3 and acceleration effect of V2O5, as well as the effect of CaCO3 and V2O5 on core losses by means of loss separation method. In addition, as for the MnZn ferrite sample with 0.1 wt% CaCO3 and 0.01 wt% V2O5 co-additives, core losses were suppressed to 46 and 664 kW/m3 corresponding to 3 MHz 10 mT and 3 MHz 30 mT at 25 °C, respectively. The state-of-the-art MnZn ferrites with ultralow core losses own potential application for high-frequency power conversion devices. [ABSTRACT FROM AUTHOR]

The microstructures and mechanical properties of cast Al-3Li- x Cu-0.2Zr alloy were investigated. The results showed that Cu addition could slightly refine the grain size of as-cast alloy. Cu element was significantly enriched at the grain boundaries, and Cu-rich intermetallic compounds were formed in the Cu-containing alloys during casting. The peak hardness increased and the time to peak ageing decreased with the increase of Cu content. Cu addition also had a pronounced influence on the precipitation behavior of Al-3Li- x Cu-0.2Zr alloys, i.e. the number density, size and distribution of T 1 -Al 2 CuLi and θ ′-Al 2 Cu phases. The tensile strength was effectively improved after 2 wt% Cu addition compared with Al-3Li-0.2Zr alloy. A good combination of strength to ductility could be obtained in Al-3Li-2Cu-0.2Zr alloy after solution and ageing 32 h at 175 °C. The precipitation-free zones (PFZs) were developed with the coarsening of δ′-Al 3 Li particles in the peak-aged (PA) and over-aged (OA) state, promoting the poor ductility and premature failure. [ABSTRACT FROM AUTHOR]

Rheo-squeeze casting combined with gas bubbling process was proved effective to improve the mechanical properties of AZ91-2 wt%Ca (AZX912) alloy. Increase of gas flow led to improvement of the quality of AZX912 semi-solid slurry and improved ductility of rheo-squeeze casting AZX912 alloy samples. Increase of applied pressure brought refinement in as-cast microstructure and reduction of porosity, as well as continuous improvement in both tensile strength and elongation. Heat treatment at 410 °C promoted dissolution of β-Mg 17 Al 12 phase, morphology modification of Al 2 Ca phase and further increase of both tensile strength and ductility. Compared with conventional squeeze casting, the mechanical properties of rheo-squeeze casting AZX912 alloy were improved by more than 20%. The improvement in mechanical properties was mainly attributed to the grain refinement in microstructure. [ABSTRACT FROM AUTHOR]

Abstract: The present study investigated the effect of cooling rate on the microstructure and mechanical properties of sand casting Mg–10Gd–3Y–0.5Zr alloy with a cooling rate range of 0.7–3.6°C/s. When the cooling rate was increased, the average grain size of α-Mg decreased from 59μm to 39μm, the volume fraction of the second phase increased from 17.6% to 24.5%, and the eutectic compound exhibited continuous network instead of coarsening discontinuous network of plate-shaped microstructure. Energy-dispersive X-ray test results suggested that solute content of RE elements (Gd and Y) was low within the area near the grain boundary of α-Mg with high cooling rate, and solid-solution reaction occurred in the sand casting process. In addition, Vickers hardness (HV) testing indicated that HV increased with the increasing cooling rate, and the volume fraction of second phase (V) played a main role in hardness of the alloys. There was a linear relationship between them, the fitting function was HV=1.25V+63.05, R 2=0.9989. Tensile strength test showed that both of ultimate tensile strength (UTS) and tensile yield strength (TYS) first increased and then decreased with the increasing cooling rate. Based on fracture observations, the types of fracture surface characteristics are correspondingly classified into three modes, transgranular, dimple-like fracture and intergranular fracture with the increasing cooling rate. [Copyright &y& Elsevier]

Abstract The microstructures and mechanical properties of cast and extruded Al-4Cu-1Li-0.4Mg-0.1Zr- x Zn alloys were investigated and the amount of Zn additions was up to 1.1 wt%. The results showed that Zn addition could bring additional MgZn 2 phases at the grain boundary and slightly refine the grain size in the as-cast alloy. The mechanical properties of extruded Al-4Cu-1Li-0.4Mg-0.1Zr -x Zn alloy increased gradually with the Zn content under different conditions. The yield strength (YS) and ultimate tensile strength (UTS) of T8 treated (stretched by 4% and aged at 150 °C for 32 h) 1.1 Zn alloy could reach 639 MPa and 666 MPa, while elongation (EL) remained at 10.9%. For alloys peak-aged at 175 °C for 32 h (T6 treated), Zn could effectively promote the precipitation of T 1 phases (Al 2 CuLi) but decrease the volume fraction of θ′ phases (Al 2 Cu) in the matrix. The coarsening of T 1 phases could be obviously suppressed by the addition of Zn under overaged condition. However, the precipitate of T 1 phases promoted by Zn under the T8 condition is not as obvious as the T6 condition. [ABSTRACT FROM AUTHOR]

This study was undertaken to evaluate the effect of heat treatment on the microstructure and mechanical properties of extruded Al–4Cu–1Li–0.4Mg–0.4Ag–0.18Zr alloy. After a three-step homogeneous treatment (480 °C/12 h + 500 °C/12 h + 540 °C/2 h), a Cu-containing secondary phase was found to be dissolved in the α-Al matrix and distributed along the grain boundary in the as-cast state. The effect of the aging temperature, aging time, and amount of pre-deformation on the mechanical properties at ambient temperature was investigated. The results showed that higher aging temperature and longer aging time resulted in higher yield strength (YS), ultimate tensile strength (UTS), and lower elongation (EL). The increase in the amount of pre-deformation significantly promoted YS of the studied alloy, at the cost of a minor decrease in EL. Among the tested samples, the one stretched by 4.5% and aged at 125 °C for 32 h exhibited the highest yield strength. Good mechanical properties, characterized by YS = 629 MPa, UTS = 663 MPa and EL = 9.2% were obtained at ambient temperature. The precipitation behavior and strengthening mechanism were also investigated. The variations in size, number density, and distribution of the T 1 (Al 2 CuLi) and θ′ (Al 2 Cu) phases under different treatment conditions were the main reason for the change in mechanical properties. [ABSTRACT FROM AUTHOR]

Effects of Sc addition on the microstructure and mechanical properties of cast Al-3Li-1.5Cu-0.15Zr alloy were investigated by microscopy methods and tensile tests. With the addition of 0.15 wt% Sc, the grain size of studied alloy in as-cast state decreased from 120 µm to 30 µm and did not grow obviously after two-step solution treatment (32 h at 500 °C+24 h at 560 °C). After aging at 175 °C for 32 h, the elongation (EL) of Sc-containing alloy reached 5.5%, which increased by 83% compared with Al-3Li-1.5Cu-0.15Zr alloy. The key factors for improvement of comprehensive mechanical properties in Al-3Li-1.5Cu-0.15Zr-0.15Sc alloy could be summarized as follows: grain refining, size reduction of δ’ phases and the precipitation of core/double-shell Al 3 (Li, Sc, Zr) composite particles. [ABSTRACT FROM AUTHOR]

Mg–Li–Zn–Gd alloys reinforced with icosahedral quasicrystal phase (I-phase) were prepared by casting and deformed by hot extrusion. The microstructure and tensile properties of as-extruded Mg–Li–Zn–Gd alloys were investigated. It is found that I-phase formed in as-cast Mg–Li–Zn–Gd alloys and was broken into small particles during extrusion. After hot extrusion, both α-Mg and β-Li phases were elongated along the extrusion direction. Dynamic recrystallization occurred in as-extruded Mg–Li–Zn–Gd alloys. Compared with Mg–9Li (L9) alloy, the improvement in mechanical properties especially the tensile strength of the as-extruded Mg–Li–Zn–Gd alloys was mainly ascribed to the formation of I-phase and their volume fraction. Moreover, the finely recrystallized grain structure can also attribute to the strength enhancement of the alloy. [ABSTRACT FROM AUTHOR]

Microstructure, mechanical properties and fracture behaviors of sand-cast Mg-4Y-3Nd-1Gd-0.2Zn-0.5Zr (wt%) alloy in different thermal conditions were investigated. The as-cast alloy was comprised of α -Mg matrix, Mg 24 Y 5 , Mg 41 Nd 5 and β 1 phases. After solution treatment at 525 °C for 6 h, the eutectics dissolved into α -Mg matrix, leading to a huge improvement of plasticity. Alloys peak-aged at 200 °C and 225 °C exhibit high strength due to fine dense β″ and β′ precipitates. Aged at 250 °C for 10 h, the precipitates in the alloy are coarse sparse coupled β 1 / β′ phases. A desirable combination of strength and ductility was obtained with 198 MPa in yield strength, 276 MPa in ultimate tensile strength and 7.6% in elongation when over-aged at 250 °C for 10 h. Alloys under different thermal conditions show different fracture behaviors, which are closely linked to the structures of both inner grains and grain boundaries. [ABSTRACT FROM AUTHOR]

The effects of electromagnetic stirring (EMS) including stirring time, applied voltage and rotational frequency on the microstructure of semisolid slurries of the Mg–Nd–Zn–(Zr) alloys were investigated. The results indicate that all of the parameters have large effects on the microstructure of the slurries. After being treated by EMS, the morphology of primary α-Mg phases in the Mg–3Nd–0.2Zn (NZ30) alloy slurries evolves from dendrite to three types: rosette, dendrite, and spheroid, while a semisolid microstructure with small and spheroidal particles is obtained in the Mg–3Nd–0.2Zn–0.4Zr (NZ30K) alloy slurries. The data for solid fraction with stirring time can be fitted to linear equations. The increase of applied voltage and rotational frequency makes the primary α-Mg phases initially refined and then coarsened. The optimal processing parameters are stirring time 120–180 s, applied voltage 300–350 V, rotational frequency ~ 20 Hz for NZ30 alloy, and stirring time 30–180 s, applied voltage ~ 350 V, rotational frequency ~ 20 Hz for NZ30K alloy. The average particle size of NZ30 alloy can be refined from ~ 879 to ~ 457 μm. Furthermore, the effects of applied voltage and rotational frequency on undercooling and melt temperature were also discussed on the basis of thermodynamic theory. [ABSTRACT FROM AUTHOR]

In this study, effect of Y on microstructure and mechanical properties of as-cast Mg–8Li–3Al–2Zn alloy was investigated. The results show that microstructure of the Mg–8Li–3Al–2Zn alloy mainly consists of α -Mg, β -Li, AlLi and MgLiAl 2 phases. With addition of Y, the Al 2 Y compound forms and increases gradually, the AlLi phase decreases and the β -Li phase increases, meanwhile, the microstructure is significantly refined and equiaxed. The addition of 1 wt% Y produces the smallest grain size. Mg–8Li–3Al–2Zn–0.5Y alloy exhibits an optimum combination of tensile properties with the ultimate tensile strength, yield strength and elongation of 153.0 MPa, 218.5 MPa and 16.9%, which are improved by about 6.4%, 13.2% and 13.4% compared with those of Mg–8Li–3Al–2Zn alloy (143.8 MPa, 193.0 MPa and 14.9%), respectively. The mechanisms of improvement are related to grain refinement and second phase strengthening. [ABSTRACT FROM AUTHOR]

Abstract: The effect of additions of 0.5–1wt% Al on grain refinement, heat treatment and mechanical properties of Mg–10Gd–3Y (wt%) alloy has been investigated. The additions of 0.6–1wt% Al showed a dramatic grain refinement effect, which is associated with the formation of the Al2(Gd0.5Y0.5) particles that act as nucleants for α-Mg grains. Compared to the Zr refined counterpart, the Al refined alloy needed to be solution treated at a higher temperature to dissolve the majority of the intermetallic particles. Subsequent ageing at low temperatures led to pronounced precipitation hardening and consequently a large improvement in strength. In the peak-aged condition, the strength of the Al refined alloy is comparable to that of the Zr refined counterpart. [Copyright &y& Elsevier]

Abstract: The microstructure, tensile properties and high cycle rotary bending fatigue behavior of low pressure sand cast (LPSC) AM-SC1 Mg alloy, solution-treated at 525, 540 and 560°C respectively and then aged at 215°C, were studied. The solution temperature has little influence on the average grain size of LPSC AM-SC1 alloy, but decreases the size and content of the residual secondary compounds when solution temperature increases. Compared with the alloy solution treated at 525 and 540°C, the alloy treated at 560°C shows obviously higher yield strength (+19MPa) and ultimate tensile strength (+24MPa), comparable elongation, and higher rotary bending fatigue strength (+8MPa). However, when the fatigue stress amplitude is higher than the fatigue strength, the 560°C solution treated alloy shows an obvious lower fatigue life. The fatigue fracture behavior of LPSC AM-SC1 alloy was discussed as well in this paper. [Copyright &y& Elsevier]