Novel approaches to produce Al2O3–TiC/TiCN–Fe composite powders directly from ilmenite

AbstractAl2O3–TiC/TiCN–Fe composite powders were successfully prepared directly from ilmenite at 1300–1400°C. The effects of Al/C ratio, sintering atmosphere, and reaction temperature and time on the reaction products were investigated. Results showed that the nitrogen atmosphere was beneficial to the reduction of ilmenite and the formation of Al2O3–TiC/TiCN–Fe composite powders. When the reaction temperature was between 600 and 1100°C, the intermediate products, TiO2, Ti3O5 and Ti4O7 were found, which changed to TiC or TiCN at higher temperature. Al/C ratio was found to affect the reaction process and synthesis products. When Al addition was 0.5mol, the Al2O3 phase did not appear. The content of carbon in TiCN rose when the reaction temperature was increased

The effect of addition of Nd and Ce on the microstructure and mechanical properties of ZM21 Mg alloy

AbstractThe microstructures and mechanical properties of Mg–2.0Zn–1.0Mn (ZM21) alloys with certain amount of Ce and Nd additions were investigated, and the influence mechanism of Ce and Nd on the microstructures and mechanical properties of extruded alloys was discussed. The results indicated that the addition of Nd and Ce can refine the grains in ZM21 alloy, for which the distribution density of second phase particle played a major role to hinder the growth of dynamic recrystallization (DRX) grain in alloys by adding a content of 0.4 wt.% Ce and Nd. The average grain size of ZM21 alloy with the additions of 0.4 wt.% Nd and Ce reached 6 ± 3 μm and 13 ± 2 μm, respectively. Adding Ce and Nd to ZM21 alloy, the changes of mechanical properties were mainly attributed to a reduction in basal texture intensity, refinement grain size as well as the dispersion density and distribution position of fine second phase particles. Furthermore, by addition of Ce and Nd to ZM21 alloy, the non-basal plane slip system could be activated which decreased the basal texture intensity

A novel approach to melt purification of magnesium alloys

AbstractA novel low-cost method for melt purification of magnesium alloys, the melt self-purifying technology (MSPT), has been developed successfully based on a low temperature melt treatment (LTMT) without adding any fluxes. The iron solubility in the molten liquid of magnesium and its alloys, and the settlement velocity of iron particles were calculated. It is shown that the low temperature melt treatment is an effective method to decrease the impurity Fe content in magnesium and its alloys. Without any additions, the Fe content in the AZ31 alloy was reduced to 15 ppm from the initial 65 ppm, and the Fe content in the AZ61 melt was decreased to 20 ppm from the initial 150 ppm after the low temperature melt treatment. The results also showed that the Fe content in AM60 and AM50 dropped to 15 and 18 ppm, respectively, from the initial 150 ppm after the low temperature melt treatment. For ZK 60, the Fe content in the melt down to less than 5 ppm was achieved. After the low temperature melt treatment, the Si content in the above alloys was also decreased obviously

Active corrosion protection by a smart coating based on a MgAl-layered double hydroxide on a cerium-modified plasma electrolytic oxidation coating on Mg alloy AZ31

A composite coating was produced via (i) plasma electrolytic oxidation (PEO) with Ce salt sealing, on which layered double hydroxides (LDHs) were deposited via a hydrothermal treatment, and (ii) then modified by phytic acid (PA) via an ion-exchange reaction. The final coating (characterized using XRD, XPS, FT-IR, SEM, EDS and GDOES) consisted of LDHs/Mg(OH)/CeO/Ce(OH) with a non-uniform Ce distribution. The corrosion protection and self-healing ability were investigated using polarization curves, EIS, immersion tests and SVET. The composite coating modified with PA showed the most superior corrosion protection and self-healing ability, attributed to the synergistic effect between Ce species and phosphate

Effect of Graphene Nanoplatelets addition on mechanical properties of pure aluminum using a semi-powder method

In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets (Al/GNPs) composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum (in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength (+14.7%), ultimate tensile strength (+11.1%) and lower failure strain (−40.6%). Surprisingly, compared to monolithic Al (in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength (−7.8%), and lower failure strain (−20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum (+11.8%). Scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively

Mechanical Properties and Microstructure of Magnesium-Aluminum Based Alloys Containing Strontium

The mechanical properties and processing performances of conventional magnesium alloys still could not meet the need of important application fields due to some demerits, such as poor formability, low creep resistance and unsatisfactory strength at elevated temperature. Recent investigations have shown that additions of strontium to magnesium alloys are effective in improving creep resistance of the alloys at temperatures above 150 C, and some new types of magnesium alloys containing strontium have been developed. The mechanical properties and microstructure of magnesium-aluminum based alloys containing strontium are reviewed, and the considerable discrepancy among the research results is discussed. Special attentions are paid to the mechanical properties, compounds and grain refinement of Mg-Al-Sr based alloys. The Sr/Al ratio is thought to be important to control the microstructure of Mg-Al-Sr alloys. The mechanism of grain refinement caused by strontium addition in magnesium alloys remains unclear

Development of high-strength, low-cost wrought Mg–2.0 mass% Zn alloy with high Mn content

Mg–Zn–Mn-based alloys have received considerable attention because of their high creep resistance, strength, and good corrosion resistance. The alloying element Mn in Mg–Zn-based alloys is commonly less than 1 wt%. In the present study, the effect of high Mn content (1 wt% and 2 wt%) on the microstructures and mechanical properties of Mg–2Zn–0.3Sr extruded alloy was investigated. The results revealed that the high Mn content significantly increased the ultimate tensile strength, tensile yield strength, compress yield strength, and yield asymmetry of the alloy without affecting its ductility. The dynamically recrystallized (DRXed) grains of Mg–2Zn–0.3Sr were remarkably refined because of the large amount of fine Mn precipitates in the homogenized alloy. The improved strengths were mainly attributed to the fine DRXed grains according to the Hall–Petch effect and to the large amount of spherical and Mn precipitates through the precipitation and dispersion strengthening. The fine DRXed grains and numerous Mn precipitates effectively suppressed the extension twining, substantially enhanced the compress yield strength, and resulted in improved anisotropy

Corrosion and Residual Strength Analysis of High Pressure Die Casting AM Series Mg Alloys

Higher pressure die casting (HPDC) AM series (Mg-Al-Mn) Mg alloys have wide application potential in the automobile industry. To promote its application, systematic investigation on the corrosion performance and corrosion residual strength of HPDC AM50+1Ce and AM60 was carried out. The corrosion of HPDC AM50+1Ce was more uniform, while the pitting corrosion of AM60 was more severe, and the mechanical properties of HPDC AM60 was more sensitive to corrosion. The residual strength of AM50+1Ce and AM60 after corrosion of 648 h was 199 MPa and 183 MPa, respectively. The findings can contribute to a better understanding of the corrosion and residual strength of HPDC AM series Mg alloys

Strengthening Effects of Zn Addition on an Ultrahigh Ductility Mg-Gd-Zr Magnesium Alloy

A newly developed Mg-2Gd-0.5Zr-xZn (x = 0.5, 1.0, 2.0, 3.0 wt %) alloy system exhibits significant strengthening by doping with Zn. In order to understand the strengthening mechanism, the microstructure, texture evolution, and mechanical properties of ultrahigh ductility Mg-2Gd-0.5Zr alloys with a Zn addition were systematically investigated. The addition of Zn results in the formation of Mg-Gd-Zn intermetallic compounds along grain boundaries, which encourages grain refinement during hot extrusion via the particle stimulated nucleation (PSN) mechanism. Furthermore, during texture sharpening the pole changes from <20 2 ¯ 1> to <01 1 ¯ 0>, which also occurred in the extruded alloys with Zn addition, which is unfavorable for the basal slip and tensile twinning. Mg-2Gd-0.5Zr-3Zn shows well-balanced strength and ductility with a tensile yield strength (YS) and ultimate tensile strength (UTS) of 285 and 314 MPa, accompanied by a high tensile elongation of 24%. They are superior to those of commercial AZ31. The enhanced strength is attributed to grain refinement, precipitation strengthening, and texture sharpening induced by alloying with Zn. The research result is also of great value to the development of low rare-earth, high strength, and high room temperature ductility magnesium alloy