Effects of minor Y,Zr and Er addition on microstructure and properties of Al-5Cu-0.4Mn alloy

The effect of different contents of Y, Zr and Er on microstructure and properties of Al-5 Cu-0.4 Mn alloy was investigated. T6 heat treatment, OM, SEM and EDS methods were applied to the alloy. The results showed that fluidity and elongation of alloy adding Y, Zr and Er were improved, while with the increase of addition amounts, θ phase increased and grains were trended to grow up gradually. The Al-5 Cu-0.4 Mn alloy presented the maxed style of ductile and brittle fracture. After T6 heat treatment, the precipitation amounts of θ phase decreased dramatically and tensile strength and hardness significantly increased. Especially when addition contents were among 0.1-0.3 wt.%, tensile strength and hardness of heat-treated alloy increased greatly, almost doubled as that of the as-cast state. The tensile strength reached its maximum of 378.43 MPa when the addition amount was 0.3 wt.%. With the further increase of addition amounts, the elongation deteriorated and the proportion of ductile fracture reduced due to the limited dispersion strengthening effect of θ phase and Al_8Cu_4 Er. It demonstrated that addition of 0.1-0.3 wt.% Y, Zr and Er would generate positive effects and influences on Al-5 Cu-0.4 Mn alloy, which is significant for optimizing components and improving properties of Al-5 Cu-0.4 Mn alloy.     

An Al-12Si/ZnS powder inoculant for eutectic silicon in Al-12Si alloy

To obtain high-performance Al-Si-based cast alloys,refinement and modification of Si phases are required.An Al-12Si/ZnS powder inoculant was designed and fabricated using a chemical bath deposition method.The efficiency of the inoculant for modifying the eutectic Si phase in as-cast Al-12Si alloy was studied.Results show that Al-12Si/ZnS powder can significantly refine the eutectic Si in Al-Si cast alloys.The best refinement effect for eutectic Si is achieved with 17.5wt.%Al-12Si/ZnS powder.Coarse long needle-shaped eutectic Si with a length of 18μm was modified into approximately spherical shape with a diameter of 6.53μm,which is evenly distributed throughout the alloy.The E2EM model calculation indicates that the inter-plane misfit(F_p)and inter-atomic spacing misfit(F_r)between ZnS and Si are all less than 0.5%,which confirms that ZnS is a potential nucleation site for Si phase.The hardness,tensile strength,and elongation of Al-12Si alloys modified with 17.5%Al-12Si/ZnS powder increase 6.30%,16.18%and 55.45%,respectively,compared to the unmodified Al-12Si alloy.The fracture behavior of the alloy with 17.5wt.%Al-12Si/ZnS powder is dominated by transgranular fracture supplemented by intergranular fracture.     

Effects of rare earth elements on microstructure and tensile properties of Al-Si-Cu alloy at 250 °C

The effects of rare earth elements (La, Sm) on the high-temperature (250 °C) microstructure and mechanical properties of Al-Si-Cu alloys were analyzed. The experimental results show that with the addition of La and Sm, the α-Al was significantly refined, and the eutectic Si changed from acicular to rod-like and granular. XRD and SEM analysis shows that the rare earth phases in the alloy were mainly AlSiRe and AlRe. Fracture morphology observations show the fracture mode of the alloy changes from brittle and ductile fracture to ductile fracture. With the increase of La or Sm contents, the mechanical properties of the alloys at 250 °C increase at first, and then decrease. When the contents of La and Sm are 0.4wt.% and 0.2wt.%, the tensile strength of the alloy reaches maximum of 143.91 MPa and 201.48 MPa, respectively.

     

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al₃(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al₃(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al₃(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.     

Effect of Al addition on microstructure and mechanical properties of Mg−Gd−Zn alloys

The microstructure evolution and mechanical properties of Mg?15.3Gd?1Zn alloys with different Al contents (0, 0.4, 0.7 and 1.0 wt.%) were investigated. Microstructural analysis indicates that the addition of 0.4 wt.% Al facilitates the formation of 18R-LPSO phase (Mg₁₂Gd(Al, Zn)) in the Mg?Gd?Zn alloy. The contents of Al₁₁Gd₃ and Al₂Gd increase with the increase of Al content, while the content of (Mg, Zn)₃Gd decreases. After homogenization treatment, (Mg, Zn)₃Gd, 18R-LPSO and some Al₁₁Gd₃ phases are transformed into the high-temperature stable 14H-LPSO phases. The particulate Al?Gd phases can stimulate the nucleation of dynamic recrystallization by the particle simulated nucleation (PSN) mechanism. The tensile strength of the as-rolled alloys is improved remarkably due to the grain refinement and the fiber-like reinforcement of LPSO phase. The precipitation of the β′ phase in the peak-aged alloys can significantly improve the strength. The peak-aged alloy containing 0.4 wt.% Al achieves excellent mechanical properties and the UTS, YS and elongation are 458 MPa, 375 MPa and 6.2%, respectively.     

Brazing of 6061 aluminum alloy/Ti-6Al-4V using Al-Si-Cu-Ge filler metals

Al-8.4Si-20Cu-10Ge and mixed rare-earth elements (Re) containing Al-8.4Si-20Cu-10Ge-0.1Re filler metals were used for brazing of 6061 aluminum alloy/Ti-6Al-4V. The addition of 20 wt.% copper and 10 wt.% germanium into the Al-12Si filler metal lowered the solidus temperature from 586 °C to 489 °C and the liquidus temperature from 592 °C to 513 °C. The addition of 0.1 wt.% rare-earth elements into Al-8.4Si-20Cu-10Ge alloy caused remarkable Al-rich phase refinement and transformed the needle-like Al₂Cu intermetallic compounds into block-like shapes. Shear strengths of the 6061 aluminum alloy/Ti-6Al-4V joints with the two brazing filler metals, Al-8.4Si-20Cu-10Ge and Al-8.4Si-20Cu-10Ge-0.1Re, varied insignificantly with brazing periods of 10-60 min. The average shear strength of the 6061 aluminum alloy/Ti-6Al-4V joints brazed with Al-8.4Si-20Cu-10Ge at 530 °C was about 20 MPa. Rare-earth elements appeared to improve the reaction of the Al-8.4Si-20Cu-10Ge filler metal with Ti-6Al-4V. The joint shear strength of the 6061 aluminum alloy/Ti-6Al-4V with Al-8.4Si-20Cu-10Ge-0.1Re reached about 51 MPa.     

Influence of Al-Ti-B addition on the microstructure and mechanical properties of A356 alloys

The mechanical properties (σb,σ0.2,and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a function of the addition level of Al-Ti-B master alloy under both as-cast and T6 heat-treated conditions. The results show that as the addition level of Al-5Ti-1B master alloy increases from 0.1 wt.% to 5.0 wt.%,the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also,they display exc...     

Effect of heat treatment on tensile and fatigue deformation behavior of extruded Al-12 wt%Si alloy

This study investigated the effect of heat treatment on tensile and high-cycle fatigue deformation behavior of extruded Al-12 wt%Si alloy. The material used in this study was extruded at a ratio of 17.7: 1 through extrusion process. To identify the effects of heat treatment, T6 heat treatment (515 °C/1 h, water quenching, and then 175 °C/10 h) was performed. Microstructural observation identified Si phases aligned in the extrusion direction in both extruded alloy (F) and heat treated alloy (T6). The average grain size of F alloy was 8.15 °C, and that of T6 alloy was 8.22 °C. Both alloys were composed of Al matrix, Si, Al₂Cu, Al₃Ni and AlFeSi phases. As T6 heat treatment was applied, Al₂Cu phases became more finely and evenly distributed. Tensile results confirmed that yield strength increased from 119.0 MPa to 329.0 MPa, ultimate tensile strength increased from 226.8 MPa to 391.4 MPa, and the elongation decreased from 16.1% to 5.0% as T6 heat treatment was applied. High-cycle fatigue results represented F alloy’s fatigue limit as 185 MPa and T6 alloy’s fatigue limit as 275 MPa, indicating that high-cycle fatigue properties increased significantly as heat treatment was conducted. Through tensile and fatigue fracture surface analysis, this study considered the deformation behaviors of extruded and heat treated Al-Si alloys in relation to their microstructures.     

Mechanical and Tribological Characterization of Al-Mg2Si Composites After Yttrium Addition and Heat Treatment

In this study, the effect of heat treatment and yttrium additions on the microstructure, mechanical properties, and tribological behavior of Al-15% Mg₂Si cast composites was investigated. The microstructural study revealed the presence of both primary and secondary Mg₂Si phases in all composite specimens and also Y-containing intermetallics (Al₂Y phases) at higher concentrations. It was also found that Y addition does not change the size and morphology of primary Mg₂Si particles considerably, but the pseudo-eutectic Mg₂Si changed from a flake-like morphology to fine fibrous or rod-like one. The results show that proper content of Y additions can reduce the amount of Mg₂Si phase through dissolving it into the matrix, lead to the precipitation of Al₂Y phase and improve the mechanical properties. Modified composites with 0.5% Y exhibited an ultimate tensile strength (UTS) of 290 MPa with an elongation of 4.3%. After exposing the composite to solution treatment at 520 °C for 4 h, the tensile strength of the composite continuously increased with the increase of Y content, and reached the maximum at 1% Y. The maximum UTS and elongation at room temperature for the heat-treated composites are 294 MPa and 7.4%, respectively. In the cast specimen, fracture surfaces are covered by packets with coarse steps, suggesting a brittle mode of failure. Modified composites with 0.5 wt.% Y contain several cracked particles together with a few decohered primary Mg₂Si particles. In solution heat-treated state, dimples present at the fracture surface are rather coarse but homogenous, showing a semi-ductile mode of fracture. Wear test results showed that the wear resistance of all specimens increases with the addition of Y up to 0.3 wt.%. Scanning electron microscopic observations of the worn surfaces revealed that the dominant wear mechanism was abrasive wear accompanied by some delamination wear mode.     

Effect of Minor Er on the Microstructure and Properties of Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr Alloys

As-cast Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr alloys containing different additions of Er were prepared. Then, the specimens were carried out homogenization heat treatment, hot rolling, cold rolling, and annealing. The effects of minor Er on the microstructure and properties of Al-6.0Mg-0.4Mn-0.1Cr-0.1Zr alloy were investigated. Results show that addition of Er can refine the microstructure and improve the mechanical properties of the alloys. As for the annealed alloys, the addition of 0.33%Er can increase the tensile strength by 29 MPa. Strength increment is mainly attributed to refinement and the precipitation of Al₃Er and Al₃(Er, Zr). Additionally, the minor Er can improve the corrosion resistance of the alloys, which can be attributed to the compact composite oxide film of Er-O and Al-O, purification, and modification.     

The Effect of Ca Content on the Microstructure,Hardness and Tensile Properties of AZ81 Mg Cast Alloy

The effects of various Ca contents (0.1-4 wt.%) on the microstructure and tensile properties of AZ81 magnesium alloy were investigated with the contribution of an analytical method. Ca addition (up to 1.0 wt.%) refined the alloy microstructure but further addition of Ca resulted in a coarse structure and introduced large dendrites within the grains. The changes in the microstructures revealed that Al₄Ca, Al₂Ca, τ-Mg₃₂(A1,Zn)₄₉ and ε-MgZn intermetallics are formed in the alloy as a result of Ca addition and Al consumption. The assessment of tensile properties of AZ81-1.0 wt.%Ca alloy showed the optimum values of yield strength and ultimate tensile strength, while AZ81-0.7 wt.%Ca alloy showed maximum elongation. The reduction in tensile properties of the cast alloy by the addition of more Ca was attributed to grain coarsening and evolution of a network of intermetallic compounds. FF study of tensile fractured surfaces indicated that Ca addition encourages brittle mode of fracture propagating through precipitated intermetallics in the structure.     

P-Cr-Ti复合变质Al-25%Si合金时Cr-Ti作用机理

采用P-Cr-Ti复合变质处理Al-25%Si(质量分数)合金,重点研究了凝固组织的变化以及Cr、Ti元素的作用机理。结果表明:与单一的P变质相比,经P-Cr-Ti复合变质后,Al-25%Si合金凝固组织中初生Si的尺寸减小了12.2%~51.7%,并且初生Si分布的均匀程度增加。Al-25%Si合金中Cr、Ti主要以TiAl_3、Ti_7Al_5Si_(12)、Al_7Cr、Al_(13)Cr_4Si_4化合物的形式存在,同时有少量的P分布在含Ti化合物中。含Ti化合物呈长条状、短杆状;含Cr化合物呈菊花状、网状,分布在初生Si之间。含Cr、Ti化合物的数量随冷却速度的增加而增加。变质处理时Al-6.5%Ti合金带入的TiAl_3相,具有使初生Si持续析出和细化初生Si的作用,但细化能力有限。凝固过程中初生Si周围形成的含Cr化合物和αCr阻止初生Si的长大与聚集,促使增加初生Si分布均匀程度。     

Ca Addition Effects on the Microstructure,Tensile and Corrosion Properties of Mg Matrix Alloy Containing 8 wt.% Mg<Subscript>2</Subscript>Si

The microstructure, tensile properties and corrosion behavior of the Mg-8 wt.% Mg₂Si-x%Ca alloy have been studied by the use of optical microscopy, scanning electron microscopy equipped with energy-dispersive spectroscopy, x-ray diffraction, standard tensile testing, polarization test and electrochemical impedance spectroscopy (EIS) measurements. Microstructural studies indicated that Ca modifies both primary and eutectic Mg₂Si phase. It was found that the average size of primary Mg₂Si particles is about 60 μm, which is dropped by about 82% in the alloy containing 0.05 wt.% Ca. By the addition of different Ca contents, Ca-rich intermetallics (i.e., CaSi₂ and CaMgSi) were formed. The modification mechanism of adding Ca during solidification was found to be due to the strong effect of CaMgSi phase as a heterogonous nucleation site, apart from CaSi₂ which was reported before, for Mg₂Si intermetallics. Tensile testing results ascertained that Ca addition enhances both ultimate tensile strength (UTS) and elongation values. The optimum amount of Ca was found to be 0.1 wt.%, which improved UTS and elongation values from about 130 MPa and 2% to 165 MPa and 5.5%, whereas more Ca addition (i.e., 3 wt.%) reduced the tensile properties of the alloy to about 105 MPa and 1.8%, which can be due to the formation of CaMgSi intermetallics with deteriorating needle-like morphology. Polarization and EIS tests also showed that the Mg-3%Si-0.5%Ca alloy pronounces as the best anti-corrosion alloy. Nevertheless, further added Ca (up to 3 wt.%) deteriorated the corrosion resistance due to predominance of worse galvanic coupling effect stemmed from the presence of stronger CaMgSi cathode in comparison with Mg₂Si. With higher Ca additions, an adverse effect was seen on corrosion resistance of the Mg-3%Si alloy, as a result of forming a weak film on the alloy specimen surface.     

Influence of Sr on microstructure and mechanical properties of ZL114 cast alloy

In the present work,the effects of trace element Sr on the microstructure,tensile properties,fractography and morphology of the eutectic Si of ZL114A (Al-7Si) cast alloy were investigated.The cast ZL114A aluminum alloy was prepared using a metal mold,and then heat treated with the T6 technique.The test results of mechanical properties show that modification element Sr can improve significantly the ultimate tensile strength,elongation and hardness of the ZL114A-T6 aluminum alloy.By adding 0.04％Sr,the values of the tensile strength Rm,elongation A and hardness HB increase from 230 MPa,1％ and 65 to the maximum of 305 MPa,8％,and 100,respectively.SEM analysis indicates that the near tensile fracture surface on longitudinal section of the ZL114A-T6 alloy reveals a transgranular fracture mode without Sr modification,while the tensile fracture is an intergranular fracture mode after Sr modification.The morphology of the eutectic Si phase is changed from acicular to fine fibrous.     

The effects of Sc on the microstructure and mechanical properties of hypo-eutectic Al−Si alloys

The eutectic Si microstructure in Al-8.5wt.%Si alloy was changed from large flakes to fine lamellar when the Sc amount in the alloy reached 0.2 wt.%. 0.8wt.%Sc was optimal in terms of attaining the best modification effect. Study on the distribution of the modifiers and measurement of the surface tension of Al-8.5wt.%Si alloy melt with added Sr, Na, and Sc modifiers, respectively, reveals that Sc modifies eutectic Si by a decrease of surface tension, while Sr and Na modify eutectic Si mainly by an impurity-induced twinning mechanism. Al-8.5wt.%Si-0.4wt.%Sc alloy displayed approximately 50 and 70% increases in tensile strength and elongation, respectively, over Al-8.5wt.%Si alloy in the cast state. It also presented approximately 65 and 70% increases in tensile strength and elongation, respectively, over Al-8.5wt.%Si alloy at a ppt heat-treated state at 200°C for 3 h.     

The study of Li effect on the microstructure and tensile properties of cast Al-Mg2Si metal matrix composite

This study is undertaken to investigate the effect of different concentrations of Li (0.03-0.35%) on the microstructure and tensile properties of Al-15 wt.%Mg₂Si in situ metal matrix composite. The results showed that 0.15 wt.% Li addition changes the morphology of primary Mg₂Si from irregular or dendritic to polyhedral shape and its average particle size decreases from 32 μm to 4 μm. Microstructural observations also depicted that the morphology of the eutectic Mg₂Si phase alters from flake-like to coral-like. Further investigations on tensile tests revealed optimum Li level (0.15%) for improving both UTS and elongation values. A study of the fracture surfaces via scanning electron microscope (SEM) revealed a brittle mode of failure in unmodified composite however the addition of 0.15%Li converts the fracture behaviour to ductile. The behaviour is explained in terms of the presence of oxide bifilms in the liquid Al alloy.     

TiB2/Al-Si-Mg-Er复合材料的组织与性能

采用重熔稀释法制备了Al-7Si-0.5Mg-0.1Er和0.5TiB₂/Al-7Si-0.5Mg-0.1Er合金,研究了TiB₂颗粒增强Al-Si-Mg-Er复合材料的组织性能。结果表明,复合材料铸态组织主要由α-Al基体、共晶Si相和TiB₂颗粒组成。TiB₂粒子的加入使Al-7Si-0.5Mg-0.1Er合金二次枝晶间距减小了7.1 μm。抗拉强度达到217.53 MPa,较Al-7Si-0.5Mg-0.1Er合金提升了12.1 %。TiB₂/Al-Si-Mg-Er复合材料的最优T6热处理工艺为530 ℃×12 h固溶+160 ℃×7 h时效,经该工艺处理后,TiB₂/Al-Si-Mg-Er复合材料抗拉强度达到319.49 MPa,相比热处理前提高了46.9%,相比Al-7Si-0.5Mg-0.1Er合金提高了5.9%;屈服强度达到266.75 MPa,相比热处理前提高了106.4%,相比Al-7Si-0.5Mg-0.1Er合金提高了14.9%。复合材料抗拉强度的提升主要源于TiB₂颗粒加入后产生的晶粒细化、变质和热处理强化。     

Interdiffusion and reaction between Zr and Al alloys from 425° to 625 °C

Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo nuclear fuels and Al cladding alloys. Interdiffusion and reactions between Zr and Al, Al-2 wt.% Si, Al-5 wt.% Si or AA6061 were investigated using solid-to-solid diffusion couples annealed in the temperature range of 425° to 625 °C. In the binary Al and Zr system, the Al₃Zr and Al₂Zr phases were identified, and the activation energy for the growth of the Al₃Zr phase was determined to be 347 kJ/mol. Negligible diffusional interactions were observed for diffusion couples between Zr vs. Al-2 wt.% Si, Al-5 wt.% Si and AA6061 annealed at or below 475 °C. In diffusion couples with the binary Al–Si alloys at 560 °C, a significant variation in the development of the phase constituents was observed including the thick τ₁ (Al₅SiZr₂) with Si content up to 12 at.%, and thin layers of (Si,Al)₂Zr, (Al,Si)₃Zr, Al₃SiZr₂ and Al₂Zr phases. The use of AA6061 as a terminal alloy resulted in the development of both τ₁ (Al₅SiZr₂) and (Al,Si)₃Zr phases with a very thin layer of (Al,Si)₂Zr. At 560 °C, with increasing Si content in the Al–Si alloy, an increase in the overall rate of diffusional interaction was observed; however, the diffusional interaction of Zr in contact with multicomponent AA6061 with 0.4–0.8 wt.% Si was most rapid.     

缓慢升温时效处理对Al-Zn-Mg-Er-Zr合金性能的影响

利用扫描电镜(SEM)、显微硬度计及电导仪研究了120℃时效的两种不同工艺对Al-5Zn-3Mg-0.1Er-0.1Zr合金力学性能及导电率的影响。结果表明,相较于直接置于120℃时效工艺,采用5 h缓慢升温至120℃时效处理的试验合金的导电率提高至30.77%IACS,硬度、抗拉强度、屈服强度和伸长率分别提升至186.6 HV0.2、538 MPa、454 MPa和17.5%。两种时效工艺处理合金的断裂方式均为韧脆混合型断裂,但5 h缓慢升温时效处理合金的韧窝密度较高,剪切面特征减少。