Age-hardening characteristic of an Al-Zn-Mg-Cu alloy produced by spray deposition

Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by spray atomization and deposition technique. GP zones and age-hardening process in the alloy were investigated using high-resolution electron microscopy （HREM）, selected area diffraction （SAD）, and differential scanning calorimetry （DSC） analysis. The results indicated that spray deposition process accelerated the aging kinetics of the alloy at an aging temperature of 120℃, thereby reducing the peak aging time to 16 h. GPⅠ and GPⅡ are the two types of zones that are major precipitates for the alloy under peak-aged condition. The precipitation sequence for the alloy is also discussed.     

Effect of thermal exposure on microstructure and mechanical properties of Al−Si−Cu−Ni−Mg alloy produced by different casting technologies

The effect of thermal exposure at 350 °C for 200 h on microstructure and mechanical properties was investigated for Al−Si−Cu−Ni−Mg alloy, which was produced by permanent mold casting (PMC) and high pressure die casting (HPDC). The SEM and IPP software were used to characterize the morphology of Si phase in the studied alloys. The results show that the thermal exposure provokes spheroidization and coarsening of eutectic Si particles. The ultimate tensile strength of the HPDC alloy after thermal exposure is higher than that of the PMC alloy at room temperature. However, the TEPMC and TEHPDC alloys have similar tensile strength around 67 MPa at 350 °C. Due to the coarsening of eutectic Si, the TEPMC alloy exhibits better creep resistance than the TEHPDC alloy under studied creep conditions. Therefore, the alloys with small size of eutectic Si are not suitably used at 350 °C.     

Effect of additional elements on aging behavior of Al-Zn-Mg-Cu alloys by spray forming

1 Introduction Spray atomization and deposition technology, also termed spray forming, has attracted considerable attention because of its excellent potential advantages in the production of structure materials: cost-effectiveness in combination with pro…     

Microdistortion behavior of Al alloy reinforced by SiCp

Al alloy reinforced with SiCp was fabricated by the method of pressureless infiltration.The effects of factors such as SiCp size,volume fraction,matrix material and heat treatment process on microdistortion behavior of Al alloy were investigated.The results show that microdistortion decreases along with lessening of SiCp size and increasing of SiCp volume fraction.Matrix material has influence on the microdistortion behavior,and solution-aging can improve the microdistortion behavior.Stress and residual strain related to microdistortion behavior were simulated by FEM.It is found that the distribution of strain and stress is not symmetrical; residual strain and stress at interface are higher than those at the other places;at the sharp-angled area of a particle,matrix has the highest strain and stress where plastic distortion is caused at first;the microdistortion and stress far from the interface are smaller.     

Flattening behavior of copper droplets in plasma spray forming

A two-dimensional axisymmetric model, with 8700 and 7500 quadrilateral elements for the fluid and substrate zone separately, was developed to simulate the impacting and flattening process. The volume of fluid technique was employed to track the interface between the air and droplet. The relationships between the droplet pre-impact parameters and the flattening time as well as the flattening ratio were investigated by altering one of the parameters while remaining the others unchanged. The results show that the droplet height reaches its minimum value at approximately half of the spreading time, which also indicates the finish of vertical fluid flow at that time. The flattening ratio increases with the increase of the three pre-impact parameters-droplet diameter, temperature and velocity, even though the flattening time decreases when the droplet velocity increase.     

Effect of spray forming on evolution of microstructure and mechanical behavior of Mg-9Al-1Zn alloy

The cylindrical billet of Mg-9Al-1Zn alloy was produced by spray forming and hot extruded at 698-723 K with an extrusion ratio of 22：1, The microstructural evolution was investigated systematically. The mechanisms of grain refinement, solubility extension of Al and Zn elements in Mg matrix, and the precipitation of the second phase β-Mg17Al12 as well as their effect on the mechanical properties of the Mg-9Al-1Zn alloy were analyzed and discussed. The results show that the spray formed Mg-9Al-1Zn alloy has homogeneous equiaxed fine grains with the average grain size of 17 μm, of which the average grain size is refined further to 5 μm due to dynamic recrystallization during hot extrusion process. The evolution of size, proportion and distribution offl-Mg17Al12 phase was also observed and analyzed. The mechanical properties for the extruded rods are improved remarkably at ambient temperature.     

TLP bonding of Ti−6Al−4V to Al 2024 using thermal spray Babbitt alloy interlayer

Thermal spray assisted transient liquid phase (TLP) bonding of Ti−6Al−4V to Al2024 alloys was investigated, where the interlayer was 80 µm Babbitt thermal spray coat on Al substrate. Thermal spray creates a rough and clean surface which leads to establishing a joint with higher strength. The optimized parameters were bonding temperature of 580 °C and bonding time of 30 and 60 min. Microstructural observation together with XRD patterns confirmed the existence of Al₂Cu, Al₂CuMg, Cu₃Ti, TiAl₃, TiAl and Mg₂Sn intermetallic compounds formed in Al weld side. On the other hand, Ti₃Al, Sn₃Ti₅ and Ti₃Sn intermetallic compounds formed in Ti side. With increasing bonding time from 30 to 60 min, although the interlayer was not completely consumed, the thickness of remained Babbitt interlayer decreased to approximately 15 µm. The study showed that shear strength of the joint reaches the high value of 57 MPa obtained at larger bonding time of 60 min.     

Dynamic recrystallization behavior of AZ61 magnesium alloy

An AZ61 alloy was subjected to hot compression at temperatures ranging from 523 K to 673 K, with strain rates of 0. 001 - 1 s^-1. Flow softening occurs at all temperatures and strain rates. There are peak and plateau stresses on flow curves. The initiation and evolution of dynamic recrystallization（DRX） were studied by the flow softening mechanism based on the flow curves and microstructural observations. A linear relationship was established between the logarithmic value of the critical strain for DRX initiation（lnεc） and the logarithmic value of the Zener-Hollomon parameter （lnZ）. The volume fraction of DRX grain （φd） is formulated as a function of the process parameters including strain rate, temperature, and strain. The calculated values of φd agree well with the values extracted from the flow curves. The size of DRX grain（d） was also formulated as a function of the Zener- Hollomon parameter. This study suggests that DRX behavior of AZ61 can be predicated from plastic process parameters.     

Enhancement of the glass forming ability of Cu−Zr−Al alloys by Ag addition

The thermal stability and glass forming ability of Cu_50-xZr₄₃Al₇Ag_x (x=0, 1, 3, 5, and 7) bulk metallic glass alloys have been investigated. The glass forming ability in the Cu−Zr−Al−Ag alloys increased proportionally to the Ag content and show good correlations with thermal parameters such as ΔT_x(=T_x-T_g), T_rg(=T_g/T₁) and γ(=T_x/(T_g+T₁)). For the Cu₄₃Zr₄₃Al₇Ag₇ alloy, fully amorphous rods of 8 mm diameter were successfully fabricated by copper mold casting. Mechanical tests on this composition revealed also remarkable properties with compressive strength around 2000 MPa and large ductility.     

Deformation mechanism of the spray formed 70Si30Al alloy during hot compression

1. Introduction The novel spray formed 70Si30Al alloy devel-oped for electronic packaging application has excel-lent physical characteristics [1-5], which include low coefficient of thermal expansion (6.8 × 10?6 K?1) that matches with that of the chip (Si or GaAs), high thermal conductivity (120 W/m·k) that represents the efficient removal of heat, and low density (2.4 g/cm3) that satisfies the requirement of lightweight in aerospace equipment and locomotive calculator (or communication de…     

Production of high strength Al-Zn-Mg-Cu alloys by spray forming process

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌ Ｚｎ ( 7×××ｓｅｒｉｅｓ)ａｌｌｏｙｓｈａｖｅｂｅｅｎｗｉｄｅｌｙｕｓｅｄｂｅｃａｕｓｅｏｆｈｉｇｈｓｔｒｅｎｇｔｈ ,ｃｏｒｒｏｓｉｏｎ ｒｅｓｉｓｔａｎｃｅａｎｄｏｔｈｅｒｇｏｏｄｐｒｏｐｅｒｔｉｅｓ[1 ,2 ] .Ｂｕｔａｐｒａｃｔｉｃａｌｃｏｎｔｅｎｔｌｉｍｉｔｏｆ7%Ｚｎ (ａｌｌｏｙｓ 70 75,71 75ａｎｄ 7475ｅｔｃ)ｉｓｉｍｐｏｓｅｄｆｏｒｃｏｎｖｅｎｔｉｏｎａｌｃａｓｔｍａｔｅｒｉａｌｓｂｅｃａｕｓｅｏｆｓｏ ｌｕｔｅｍａｃｒｏ ｓｅｇｒｅｇａｔｉｏｎａｎｄｃｏａｒ…     

Age softening phenomenon and microscopic mechanism of Li−B alloy

The age softening phenomenon of the Li−B alloy was investigated by a series of tensile tests under various aging conditions. The results show that the tensile strength of the rolled Li−B alloy decreases with increasing aging time. Higher aging temperature accelerates the softening process, and leads to an early end of aging. A model was proposed to analyze the mechanism of the age softening. The vacancy annihilation is the control factor of age softening. The strength−temperature relationship was estimated by the newly proposed model and a standard heat treatment, annealing at 150 °C for 1 h, was designed to eliminate the age softening of rolled Li−B alloy.     

Grain-refining persistency of Al-based alloy produced by electrolyzing

The Al-based alloy with equiaxed grains was directly produced in the industrial aluminum electrolyzer. The varieties of grain features and grain sizes vs the re-melting times of this alloy were investigated. The grain features and mechanical properties of A356 alloy made from this alloy during the several re-melted times were also studied. The results show that the Al-based alloy after re-melted for 6 times, and A356 after re-melted for 3 times, both remained and refined grains and A356 alloy could achieve favorable mechanical properties. All these should be attributed to the electrolyzing procedure, in which nucleates, such as Al3Ti, are distributed fully and even in the based alloy. Producing Al-based alloy in the industrial electrolyzer provides a new, efficient and practical grain-refining route.     

Phase transition of Al-Fe-V-Si heat-resistant alloy by spray deposition

1　INTRODUCTIONAtpresent ,rapidlysolidifiedAl Fe V Siheat resistantalloyisgenerallypreparedby planarflowcasting ,andisonlyveryrarelypreparedbysprayingdeposition .Thecoolingrateofsprayingdepositionisslowerthanthatofplanarflowcasting ,itmusthasgivenimportanteffecttothealloys phaseconstitutesandphasetransition[112 ] .Thispaperaimsatreportingtheresearchonfor mationandtransitionofheat resistantphasesinAl Fe V Si (closetoAA80 0 9)alloy .2　PHASETRANSITIONINEQUILIBRIUMCON DITIO…     

Intermetallic phase formation in directionally solidified Al−Si−Fe alloy

The present study has been undertaken to better understand the solidification behavior of Al−Si−Fe alloys containing 7wt.% Si and 0.9wt.% Fe, with particular regard to the formation of phase during controlled solidification and influence of growth rates on intermetallic phase selection. The alloys studied were Al-7Si-0.9Fe alloys, which were produced by a modified Bridgman solidification arrangement. These alloys were solidified unidirectionally with different growth rates (1–30mm/min). The solidified microstructure of these alloys consists of the growth of primary aluminum and multiple second phase reactions.     

Controlled semisolid microstructures and mechanical properties of Al–Mg–Si–Mn wrought alloy produced by D-SSF

Abstract

The semisolid microstructures and the mechanical properties of Al–1˙35Mg–1˙04Si–0˙67Mn alloy produced by deformation semisolid forming (D-SSF) process were studied. Fine α-Al₁₅Mn₃Si₂ compounds precipitate homogeneously during the homogenisation treatment. These compounds effectively inhibit the coarsening of recrystallised grains during heating to the semisolid temperature. When the liquid fraction is controlled to be ～23%, the complete die filling is not achieved. Therefore, in order to achieve good fluidity, it is necessary to control the liquid fraction to be more than 30%. The average grain size and the liquid fraction at the semisolid temperature influence directly mechanical properties. Therefore, the relationship among the average grain size, the liquid fraction at the semisolid temperature and mechanical properties was evaluated. Furthermore, the optimum semisolid microstructure was determined and the condition for the D-SSF process was established.     

Effect of Si content on surface hardening of Al–Si alloy by shot peening treatment

The effect of Si content was investigated for Al–Si alloys (Al-7%, 11%, 18%Si) by shot peening process. The hardness increment by shot peening increased as the Si contents in Al–Si alloys increased. Finer Si particles and more dense distribution of those were observed in Al–18%Si than Al–7%Si. As Si contents of Al–Si alloys increased, grain size at the surface area of Al–Si alloy decreased. Higher hardness of Al–Si alloy with higher Si content could be attributable to more dense and refine Si particles and accelerated grain refinement during severe deformation.     

Study of strain softening behavior of Al–Al3Sc multilayers using microcompression testing

Multilayer thin films with bilayer thicknesses in the nanometer range have been reported to have very high strengths. A previous study has shown that Al–Al₃Sc multilayers, with bilayer thicknesses as small as 6 nm, have hardnesses as high as ～3 GPa as measured by sharp tip nanoindentation. In the present study, we have avoided some of the complications associated with sharp tip nanoindentation by directly measuring the yield strengths and strain hardening/softening properties of Al–Al₃Sc multilayers using microcompression testing methods with a nanoindenter. The results show the expected trend of increasing yield strength with decreasing bilayer thickness, and compare favorably with estimates of the yield strengths based on sharp tip nanoindentation. During deformation, the Al–Al₃Sc multilayer pillars with smaller bilayer spacings experience considerable strain softening, resulting in a “flat-top mushroom” shape after deformation. We have developed a numerical model to account for this inhomogeneous deformation behavior and to calculate stress–strain relationships during strain softening. A new transmission electron microscopy study of a deformed pillar shows that the softening is a result of destruction of the layered structure due to shearing and rotation.     

Research on flow stress of spray formed 70Si30Al alloy under hot compression deformation

1. Introduction New spray formed 70Si30Al alloy developed for electronic packaging application has excellent physical characteristics [1-5], which include low coefficiency of thermal expansion (6.8 × 10?6/K), high thermal conductivity (120 W/(m?K)), and low density (2.4 g/cm3), therefore, the exploitation and application of the alloy have an extensive prospect. To evaluate the deformation characteristics of spray formed 70Si30Al and to determine the appropriate hot deformation procedure of …     

Softening produced by the microstructural instability of the intermetallic alloy Ti–46.5Al–2W–0.5Si

The influence of heat treatments on the softening process of a TiAl intermetallic alloy containing three phases (namely γ, α₂ and B2) has been examined. At the annealing temperatures studied, the lamellar microstructure exhibits faster softening kinetics than the globular one due to the transformation that takes place between the α₂ and B2 phases while the globular structure softens by a coarsening/dissolution process of the respective B2 and α₂ globules initially present.