Influence of Cu Addition on the Structure,Mechanical and Corrosion Properties of Cast Mg-2%Zn Alloy

Effects of different concentrations of Cu on the structure, mechanical and corrosion properties of Mg-2%Zn alloy were studied by the use of x-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, standard tensile testing, polarization and electrochemical impedance spectroscopy (EIS) measurements. The average grain size of the alloy decreased from above 1000 μm to about 200 μm with 5 wt.% Cu addition in as-cast condition. Microstructural studies revealed that Mg-2Zn-xCu alloys matrix typically consists of primary α-Mg and MgZnCu and Mg(Zn,Cu)₂ intermetallics which are mainly found at the grain boundaries. The results obtained from mechanical testing ascertained that Cu addition increased the hardness values significantly. Although the addition of 0.5 wt.% Cu improved the ultimate tensile strength and elongation values, more Cu addition (i.e., 5 wt.%) weakened the tensile properties of the alloy by introducing semi-continuous network of brittle intermetallic phases. Based on polarization test results, it can be concluded that Cu eliminates a protective film on Mg-2%Zn alloy surface. Among Mg-2%Zn-x%Cu alloys, the one containing 0.1 wt.% Cu exhibited the best anti-corrosion property. However, further Cu addition increased the volume fraction of intermetallics culminating in corrosion rate enhancement due to the galvanic couple effect. EIS and microstructural analysis also confirmed the polarization results.     

Effect of Cu on microstructure,mechanical properties,and texture evolution of ZK60 alloy fabricated by hot extrusion−shearing process

As-cast Mg−6Zn−xCu−0.6Zr (x=0, 0.5, 1.0, wt.%) alloys were fabricated by permanent mold casting; then, the alloys were subjected to homogenization heat treatment and extrusion−shearing (ES) process. The microstructure and mechanical properties of the alloys were evaluated by OM, SEM/EDS, XRD, TEM, EBSD and tensile tests. The results show that the hard MgZnCu phase in Cu-added alloy can strengthen particle-stimulated nucleation (PSN) effect and hinder the migration of dynamic recrystallization (DRX) grain boundary at an elevated temperature during ES. The ZK60+0.5Cu alloy shows an optimal tensile strength–ductility combination (UTS of 396 MPa, YS of 313 MPa, and δ=20.3%) owing to strong grain boundary strengthening and improvement of Schmid factor for {0001} basal slip. The aggregation of microvoids around the MgZnCu phase mainly accounts for the lower tensile elongation of ZK60+1.0Cu alloy compared with ZK60 alloy.     

Microstructures and Properties of Extruded Mg-Gd-Y-Zr Alloys Containing Zn

Microstructure and mechanical properties of Mg-10Gd-3.8Y-xZn-0.5Zr (x?=?0, 1, 3?wt.%) alloys during extrusion and following isothermal aging at 200?°C were investigated using digital microhardness testing, mechanical testing, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD). The results showed that Zn can refine grains of the alloy, and improved mechanical properties of the as-extruded alloys. In T5 (peak-aging) condition, the average grains of the alloy without Zn addition were about 20.10???m; the average grains of the alloys with 1?wt.% Zn addition and 3?wt.% Zn addition were about 15.35 and 10.04???m, respectively. For the alloy with 1?wt.% Zn addition in as-extruded and peak-aged states, the values of tensile strength reached 345 and 429?MPa, yield strength reached 260 and 342?MPa, as well as ductility rate reached 10.8 and 5.7%, respectively, exhibiting superior mechanical properties.     

Microstructure,anticorrosion, biocompatibility and antibacterial activities of extruded Mg−Zn−Mn strengthened with Ca

To find suitable biodegradable materials for implant applications, Mg?6Zn?0.3Mn?xCa (x=0, 0.2 and 0.5, wt.%) alloys were prepared by semi-continuous casting followed by hot-extrusion technique. The microstructure and mechanical properties of Mg?6Zn?0.3Mn?xCa alloys were investigated using the optical microscope, scanning electron microscope and tensile testing. Results indicated that minor Ca addition can slightly refine grains of the extruded Mg?6Zn?0.3Mn alloy and improve its strength. When 0.2 wt.% and 0.5 wt.% Ca were added, the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2 μm, respectively. Of the three alloys studied, the alloy with 0.5 wt.% Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%. The corrosion behaviour, cell viability and antibacterial activities of alloys studied were also evaluated. Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca₂Mg₆Zn₃ phases. Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg?6Zn?0.3Mn?0.5Ca alloy compared to Mg?6Zn?0.3Mn and Mg?6Zn?0.3Mn? 0.2Ca alloys. The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.     

Effects of Mg content on microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys

Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al?xMg? 3Zn?1Cu cast alloys (x=3?5, wt.%) were investigated. As Mg content increased in the as-cast alloys, the grains were refined due to enhanced growth restriction, and the formation of η-Mg(AlZnCu)₂ and S-Al₂CuMg phases was inhibited while the formation of T-Mg₃₂(AlZnCu)₄₉ phase was promoted when Mg content exceeded 4 wt.%. The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates. As Mg content increased, the yield strength and tensile strength of the as-cast, solution-treated and peak-aged alloys were severally improved, while the elongation of the alloys decreased. The tensile strength and elongation of the peak-aged Al?5Mg?3Zn?1Cu alloy exceed 500 MPa and 5%, respectively. Precipitation strengthening implemented by T′ precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.     

Effects of Cu content on microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys

A systematic study on how Cu content affects the microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys during solution treatment and ageing heat treatment was conducted. The swirled enthalpy equilibrium device (SEED) was adopted to prepare the semi-solid slurry of Al-6Zn-2Mg-xCu alloys. The microstructure development and mechanical properties were studied using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), as well as hardness and tensile testing. The grain boundary and shape factor were calculated using image processing software (Image-Pro Plus 6.0). Results show that the alloys are composed of typical globular primary α-Al grains, eutectic phases, and smaller secondary α-Al grains. After solution and ageing heat treatment, the eutectic phases are dissolved into Al matrix when the Cu content is lower than 1.5wt.%, while some eutectic phases transform into Al₂CuMg (S) phases and remain at grain boundaries when Cu content reaches 2wt.%. T6 heat treatment significantly enhances the mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys. When Cu concentration is 0.5wt.%–1.5wt.%, the ultimate tensile strength, yield strength and elongation of T6 treated alloys rise to around 500 MPa, 420 MPa, and 18%, respectively.

     

Microhardness and Tensile Properties of a 6XXX Alloy Through Minor Additions of Zr

The 6XXX series alloy is known to show inferior age-hardening response during the paint-bake cycle due to natural aging prior to the paint-bake. Many researchers have adopted the pre-aging process to offset the detrimental effect of the natural aging process. The alloy used in this study contained excess Si, and it had been reported elsewhere that such alloys do not show positive response to the pre-aging process. The present work is aimed to study the microhardness and tensile strength of the Al-1.2Si-0.5Mg-0.25Fe wrought alloy through Zr additions between 0.02 and 0.30 wt.%. Alloys containing 0.15 wt.% Zr and above heat-treated for 30 min gave higher microhardness and ultimate tensile strength values compared to that of Al-1.2Si-0.5Mg-0.25Fe without Zr which was heat-treated for 11 h. It was found that mechanical properties improved when the Zr content in the alloys increased. The improvement of mechanical properties was mainly attributed to formation of Zr-bearing intermetallic compounds formed in the alloy.     

Effect of Zn additions on the age-hardening of Mg–2.0Gd–1.2Y–0.2Zr alloys

We have investigated the microstructures of age hardened Mg–2.0Gd–1.2Y–xZn–0.2Zr (x = 0, 0.3, and 1.0) (at.%) alloys to understand the remarkable age-hardening and unusual plastic elongation behavior. The age-hardening of the alloys occurs through the sequential precipitations of β′ and β₁ phases. The β₁ phase heterogeneously nucleates at the interface of the β′ phase, and relaxes strain fields around the β′. Although the addition of Zn degrades the age-hardening response, it causes the discontinuous precipitation of a 14H-type long-period stacking (LPS) phase at grain boundaries as well as within grains in the over-aged condition, which enhances the maximum tensile elongation. The composition of the β₁ phase was determined to be Mg–23.3 at.% RE–9.7 at.% Zn–2.0 at.% Zr (RE: rare-earth, Gd and Y), whereas that of the LPS is Mg–5.6 at.% RE–1.8 at.% Zn–1.0 at.% Zr.     

Effect of Ce on microstructure, mechanical properties and corrosion behavior of high-pressure die-cast Mg-4Al-based alloy

Mg-4Al-xCe-0.3Mn (x = 0, 1, 2, 4 and 6 wt.%) alloys were prepared by high-pressure die-casting. The microstructures, mechanical properties and corrosion behavior were investigated. The cross-section of test bar is divided into the fine skin region and the relatively coarse interior region by a narrow band. The dendritic arm spacing is greatly reduced and the secondary phases Al₁₁Ce₃ and (Al, Mg)₂Ce with the former being the dominant one substitute the Mg₁₇Al₁₂ phase with addition of Ce. When Ce content reaches 4 wt.%, the alloy exhibits an optimal cost performance ratio. The improved mechanical properties maintained up to 200 °C are mainly related to the fine grain size and the main strengthening phase Al₁₁Ce₃, which is present in a high volume fraction, and possesses fine acicular morphology and relatively good thermal stability. The improved corrosion resistance is attributed to the microstructure modification of the alloys and the corrosion product films.     

通过双级固溶热处理制备新型高强Al−10.5Si−3.4Cu−0.2Mg合金

通过析出硬化提高Al?Si?Cu合金的力学性能.这些合金对时效硬化的反应非常缓慢.为了解决这一问题,在Al?10.5Si?3.4Cu合金中分别加入0.2％、0.4％和0.7％(质量分数)的镁.该新型合金在固溶处理阶段经过两种不同的析出硬化过程.结果表明,添加不同含量的镁可加速该合金对时效处理的响应,提高其硬度和强度.双...     

Feasibility study on utilizing carbon dioxide during the processing of Mg-Al alloys

The feasibility of utilizing carbon dioxide (CO₂) during magnesium-aluminium (Mg-Al) alloys processing was investigated by incorporating CO₂ gas during melting and casting of the alloys. Mg-Al alloys containing ∼3 wt.% and ∼5 wt.% Al were processed with and without CO₂ atmosphere using the disintegrated melt deposition (DMD) technique. The cast alloys after extrusion were characterized for their structural, physical and mechanical properties to identify the utilization of carbon dioxide during processing. Results indicated that sound, defect-free Mg-Alloys were produced with CO₂ processing. Improvement in mechanical properties such as hardness, tensile strength and compressive yield strength were observed. The in situ formation of Al₄C₃ phase during processing was identified as the reason for the improvement in the properties, which indicated the utilization of carbon dioxide by the melt.     

Structure and high-temperature oxidation behaviour of Cu-Ni-Fe alloys prepared by high-energy ball milling for application as inert anodes in aluminium electrolysis

Cu_xNi_85−xFe₁₅ (0 ? x ? 85 wt.%) compounds were prepared by mechanical alloying. Monophased face centered cubic (fcc) Cu-Ni-Fe alloys were obtained after 10 h of milling for x varying from 0 to 50, whereas bi-phased compounds fcc Cu-Ni-Fe + body centered cubic (bcc) Fe were formed with richer-Cu compounds. Their oxidation kinetics in air at 750 °C is parabolic for all compositions and increases drastically for x > ∼30. A stable anode for aluminium electrolysis in low-temperature (700 °C) KF-AlF₃ electrolyte was obtained for 65 ? x ? 85. However, a substantial increase of the Cu contamination in produced aluminium was observed for x > 70.     

Influence of silver addition on the microstructure and mechanical properties of squeeze cast Mg-6Al-1Sn-0.3Mn-0.3Ti

In this study, the effect of silver (0, 0.2, 0.5, and 1 wt.%) on the microstructure and mechanical properties of a magnesium-based alloy (Mg-Al 6 wt.%-Sn 1 wt.%-Mn 0.3 wt.%-Ti 0.3 wt.%) were investigated. The alloys were produced under a controlled atmosphere by a squeeze-casting process. X-ray diffractometry revealed that the main phases are α-Mg, α-Ti, β-Mg₁₇Al₁₂ and Al₈Mn₅ in the all of alloys. In addition to, Al₈₁Mn₁₉ phase was found with Ag additive. Besides, the amount of β-Mg₁₇Al₁₂ phase was decreased with increasing the amount of Ag. The strength of the base alloy was increased by solid solution mechanism and decreasing the amount of β-Mg₁₇Al₁₂ phase with addition of Ag. Furthermore, existence of Al₈₁Mn₁₉ phase can be acted an important role in the increase on the mechanical properties of the alloys.     

Combined effects of Bi and Sb elements on microstructure,thermal and mechanical properties of Sn-0.7Ag-0.5Cu solder alloys

This research investigated the combined effects of addition of Bi and Sb elements on the microstructure, thermal properties, ultimate tensile strength, ductility, and hardness of Sn-0.7Ag-0.5Cu (SAC0705) solder alloys. The results indicated that the addition of Bi and Sb significantly reduced the undercooling of solders, refined the β-Sn phase and extended the eutectic areas of the solders. Moreover, the formation of SbSn and Bi phases in the solder matrix affected the mechanical properties of the solder. With the addition of 3 wt.% Bi and 3 wt.% Sb, the ultimate tensile strength and hardness of the SAC0705 base alloy increased from 31.26 MPa and 15.07 HV to 63.15 MPa and 23.68 HV, respectively. Ductility decreased due to grain boundary strengthening, solid solution strengthening, and precipitation strengthening effects, and the change in the fracture mechanism of the solder alloys.     

Development of high strength Sn-0.7Cu solders with the addition of small amount of Ag and In

Nowadays, a major concern of Sn-Cu based solder alloys is focused on continuously improving the comprehensive properties of solder joints formed between the solders and substrates. In this study, the influence of Ag and/or In doping on the microstructures and tensile properties of eutectic Sn-0.7Cu lead free solder alloy have been investigated. Also, the effects of temperature and strain rate on the mechanical performance of Sn-0.7Cu, Sn-0.7Cu-2Ag, Sn-0.7Cu-2In and Sn-0.7Cu-2Ag-2In solders were investigated. The tensile tests showed that while the ultimate tensile strength (UTS) and yield stress (YS) increased with increasing strain rate, they decreased with increasing temperature, showing strong strain rate and temperature dependence. The results also revealed that with the addition of Ag and In into Sn-0.7Cu, significant improvement in YS (∼255%) and UTS (∼215%) is realized when compared with the other commercially available Sn-0.7 wt. % Cu solder alloys. Furthermore, the Sn-0.7Cu-2Ag-2In solder material developed here also exhibits higher ductility and well-behaved mechanical performance than that of eutectic Sn-0.7Cu commercial solder. Microstructural analysis revealed that the origin of change in mechanical properties is attributed to smaller β-Sn dendrite grain dimensions and formation of new inter-metallic compounds (IMCs) in the ternary and quaternary alloys.     

Effect of Gd content on microstructure and dynamic mechanical properties of solution-treated Mg−xGd−3Y−0.5Zr alloy

The effect of Gd content ranging from 6.5 wt.% to 8.5 wt.% on microstructure evolution and dynamic mechanical behavior of Mg?xGd?3Y?0.5Zr alloys was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy and split Hopkinson pressure bar. The microstructure of as-cast Mg?xGd?3Y?0.5Zr alloys indicates that the addition of Gd can promote grain refinement in the casting. Due to the rapid cooling rate during solidification, a large amount of non-equilibrium eutectic phase Mg₂₄(Gd,Y)₅ appears at the grain boundary of as-cast Mg?xGd?3Y?0.5Zr alloys. After solution treatment at 520 °C for 6 h, the Mg₂₄(Gd,Y)₅ phase dissolves into the matrix, and the rare earth hydrides (REH) phase appears. The stress?strain curves validate that the solution-treated Mg?xGd?3Y?0.5Zr alloys with optimal Gd contents maintain excellent dynamic properties at different strain rates. It was concluded that the variation of Gd content and the agglomeration of residual REH particles and dynamically precipitated fine particles are key factors affecting dynamic mechanical properties of Mg?xGd?3Y?0.5Zr alloys.     

Effects of titanium addition on structural,mechanical, tribological,and corrosion properties of Al−25Zn−3Cu and Al−25Zn−3Cu−3Si alloys

To investigate the effect of grain refinement on the material properties of recently developed Al−25Zn−3Cu based alloys, Al−25Zn−3Cu, Al−25Zn−3Cu−0.01Ti, Al−25Zn−3Cu−3Si and Al−25Zn−3Cu−3Si−0.01Ti alloys were produced by permanent mold casting method. Microstructures of the alloys were examined by SEM. Hardness and mechanical properties of the alloys were determined by Brinell method and tensile tests, respectively. Tribological characteristics of the alloys were investigated by a ball-on-disc type test machine. Corrosion properties of the alloys were examined by an electrochemical corrosion experimental setup. It was observed that microstructure of the ternary A1−25Zn−3Cu alloy consisted of α, α+η and θ (Al₂Cu) phases. It was also observed that the addition of 3 wt.% Si to A1−25Zn−3Cu alloy resulted in the formation of silicon particles in its microstructure. The addition of 0.01 wt.% Ti to the Al−25Zn−3Cu and Al−25Zn−3Cu−3Si alloys caused a decrement in grain size by approximately 20% and 39% and an increment in hardness from HRB 130 to 137 and from HRB 141 to 156, respectively. Yield strengths of these alloys increased from 278 to 297 MPa and from 320 to 336 MPa while their tensile strengths increased from 317 to 340 MPa and from 334 to 352 MPa. Wear resistance of the alloys increased, but corrosion resistance decreased with titanium addition.     

Microstructure and Mechanical Properties of Mg-8Li-(0, 1, 2)Ca-(0, 2)Gd Alloys

A series of new Mg-8Li-xCa-yGd (x = 0, 1, 2; y = 0, 2; wt.%) alloys were prepared, and the microstructure and mechanical properties were investigated. The mechanical properties were characterized by tensile, compression and bending tests at room temperature. The results show that Mg-8Li-1Ca alloy is composed of alpha(Mg), beta(Li) and CaMg₂ phases. In addition to the same phases in Mg-8Li-1Ca, there also exists CaLi₂ phase in Mg-8Li-2Ca. In addition to the same phases in Mg-8Li-2Ca, GdMg₅ phase is also formed in Mg-8Li-1Ca-2Gd alloy due to the addition of Gd. Both Ca and Gd have refining effect in the alloys, and the refining effect of Ca is better than that of Gd. The additions of Ca and Gd can improve the tensile strength and yield strength, but decrease the elongation and the bending strength. Comparing the mechanical properties of the investigated alloys, Mg-8Li-1Ca-2Gd possesses the best mechanical properties.     

Compositional dependence of phase formation and mechanical properties in three CoCrFeNi-(Mn/Al/Cu) high entropy alloys

Starting from three typical equiatomic CoCrFeNiMn, CoCrFeNiAl and CoCrFeNiCu high entropy alloys (HEAs), we systematically investigated the compositional dependence of phase formation and mechanical properties of 78 alloys by varying the atomic ratio of the constituent elements. It was found that the simple phase structures, including a single face-centered cubic (FCC) or body-centered cubic (BCC) phase, duplex FCC phases, duplex BCC phases, instead of intermetallics, could form within a broad compositional landscape in 68 out of the 78 alloys not limited to the equiatomic composition where the configurational mixing entropy is maximum. This fact indicates that it may be the nature of the constituent elements that leads to simple phase structure formation. With compositional variation, the microstructure and mechanical properties including hardness and tensile properties show corresponding changes. It was found that the hardness variation of samples within the same structure is smaller for the FCC than that of the BCC. Tensile results indicated that the tensile elongation of (CoCrFeMn)_(100−x)Ni_x (x = 0, 10 and 20) alloys increases with Ni addition due to the decreasing volume fraction of sigma phase. For the (CoCrFeAl)_(100−x)Ni_x (x = 27.3, 33.3, 38.5, 42.9 and 50) alloys, the yield strength decreases and tensile elongation increases with Ni addition due to decreasing volume fraction of BCC phase which is hard yet brittle. The present results are important to understand the phase formation and relationship between microstructure and mechanical properties in HEAs.