Effect of ECAP temperature on microstructure and mechanical properties of Al–Zn–Mg–Cu alloy

The effect of equal channel angular pressing(ECAP) at different temperatures(room temperature, 120,150 and 180 °C) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. Microstructure of the specimens was examined using orientation imaging microscopy,transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. Microstructural investigations showed that after3 or 4 passes of ECAP, fi ne grains with average grain sizes in range of 300–1000 nm could be obtained at different ECAP temperatures. Increasing ECAP temperature from 120 to 180 °C caused a decrease in mechanical properties as a result of increasing grains and precipitates sizes, decreasing fraction of high angle boundaries and also transformation of η′ into η phase, while increasing ECAP temperature from RT to 120 °C leads to an increase in mechanical properties due to the formation of small η′ precipitates. So it can be concluded that ECAP process at 120 °C is the optimum process for attaining maximum mechanical properties. Quantitative estimates of various strengthening mechanisms revealed that the improvement of mechanical properties was mainly attributed to grain re fi nement strengthening, precipitation strengthening and dislocation strengthening.     

Effects of gadolinium addition on the microstructure and mechanical properties of Mg-9Al alloy

This research aims to study the significance of Gd addition (0wt%-2wt%) on the microstructure and mechanical properties of Mg-9Al alloy. The effect of Gd addition on the microstructure was investigated via X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The Mg-9Al alloy contained two phases, α-Mg and β-Mg17Al12. Alloying with Gd led to the emergence of a new rectangular-shaped phase, Al₂Gd. The grain size also decreased marginally upon Gd addition. The ultimate tensile strength and microhardness of Mg-9Al alloy increased by 23% and 19%, respectively, upon 1.5wt% Gd addition. We observed that, although Mg-9Al-2.0Gd alloy exhibited the smallest grain size (181 μm) and the highest dislocation density (5.1×1010 m-2) among the investigated compositions, the Mg-9Al-1.5Gd alloy displayed the best mechanical properties. This anomalous behavior was observed because the Al₂Gd phase was uniformly distributed and present in abundance in Mg-9Al-1.5Gd alloy, whereas it was coarsened and asymmetrically conglomerated in Mg-9Al-2.0Gd.     

Effect of Zn addition on microstructure and mechanical properties of an Al–Mg–Si alloy

In the present work, an Al–0.66Mg–0.85Si–0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction(EBSD), high resolution electron microscopy(HREM), tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(Ⅱ) zones and η’phases were formed during aging process due to Zn addition. With the precipitation of GP zones, β″ phases, GP(Ⅱ) zones and η’phases, the alloys displayed excellent mechanical properties.     

Effect of Al on microstructure and mechanical properties of as-extruded Mg–1Mn alloy sheet

The effect of Al addition on microstructure and mechanical properties of hot extruded Mg–1 Mn alloy sheet was investigated. The results revealed that the dynamic recrystallization was promoted by increasing Al content. The ultimate tensile strength and yield strength of the alloy increased with the increase of Al content. The Mg–9 Al–1 Mn alloy exhibited the highest strength, with tensile strength of 308 MPa, 307 MPa, 319 MPa, yield strength of 199 MPa, 207 MPa, 220 MPa and the elongation of 20.9%, 20.1%, 19.2% in 0°, 45°, 90°, respectively.The high strength was mainly attributed to the formation of fine dynamically recrystallized grains and large amounts of the second phase. The strengthening mechanism of the alloys was explained.     

Effect of particle size distribution on the microstructure,texture, and mechanical properties of Al–Mg–Si–Cu alloy

The effect of particle size distribution on the microstructure, texture, and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties, microstructure, and texture of the alloy. The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture. After the pre-aging treatment and natural aging treatment (T4P treatment), in contrast to the sheet with a uniform particle size distribution, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio (r) and strain hardening exponent (n). After solution treatment, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution. Additionally, they possess almost identical weak recrystallization textures, and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.     

Effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy

The effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties,microstructure,and texture of the alloy.The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture.After the pre-aging treatment and natural aging treatment(T4 P treatment),in contrast to the sheet with a uniform particle size distribution,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio(r) and strain hardening exponent(n).After solution treatment,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution.Additionally,they possess almost identical weak recrystallization textures,and their textures are dominated by CubeND {001}310 and P {011}122 orientations.     

Effects of P addition on the microstructure and mechanical properties of Mg–5%Sn–1.25%Si alloy

The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg, Mg2 Sn, Mg2 Si, little P, and AlP. The Chinese character shape Mg2 Si phase changes into a granular morphology by P addition because AlP can act as a heterogeneous nucleation core for the Mg2 Si phase. When 0.225wt% of Al–3.5%P alloy is added, the mechanical properties of the Mg–5%Sn–1.25%Si alloy are greatly improved, and the tensile strength increases from 156 to 191 MPa, an increase of 22.4% compared to the alloy without P addition. When the amount of Al–3.5%P reaches 0.300wt%, a segregation phenomenon occurs in the granular Mg2 Si phase, and the tensile strength and hardness decrease though the elongation increases.     

Effects of intermediate Ni layer on mechanical properties of Al–Cu layered composites fabricated through cold roll bonding

Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature (either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.     

Effect of pre-annealing treatment on the microstructure and mechanical properties of extruded Al-Zn-Mg-Cu alloy bars

Taking extruded Al-Zn-Mg-Cu alloy (7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigated. The results show that a pre-annealing treatment at 350℃ for 15 h before a T6 treatment substantially reduced the sensitivity of the microstructure and mechanical properties of the extruded 7A04 aluminum alloy specimens toward the extrusion temperature. The average grain sizes of the specimens extruded at 390 and 430℃ after T6 treatment were 3.4 and 8.1 μm, respectively, and their elongations to failure were 7.0% and 9.2%, respectively. However, after pre-annealing + T6 treatment, the differences in both the grain sizes and the elongations of the specimens became small, i.e., their average grain sizes were 3.2 and 3.8 μm and their elongations were 12.0% and 13.3%, respectively. For the specimens extruded at the same temperature, pre-annealing treatment obviously improved the plasticity of the alloy, which is attributed to an increase in soft texture or to grain refinement in the specimens as a result of the pre-annealing + T6 treatment.     

Influence of different rolling processes on microstructure and strength of the Al–Cu–Li alloy AA2195

The influence of different rolling processes on precipitation behaviour, crystallography texture, grain morphology, and their consequent effects on tensile properties for Al–Cu–Li alloy AA2195 was investigated in the present work. The H-T8 samples (hot rolled ?+ ?T8) presented better tensile strength and ductility (with serious strength anisotropy) than the HC-T8 samples (hot rolled ?+ ?cold rolled ?+ ?T8), due to their different microstructures and textures. The higher dislocation density was found in the H-T8 samples, which promoted the nucleation of main strengthening phase T₁ in the matrix and suppressed the grain boundary precipitation, resulted in better strength and ductility. The increase of the dynamic recovery (DRV) during hot rolling enhanced the generation of Brass texture, and brought serious strength anisotropy. The cold rolling was performed after the hot-rolling process for the HC-T8 samples which increased deformation energy and resulted in full recrystallization of the deformed microstructure during the following solution treatment. The formation of recrystallized microstructure reduced the dislocation density and the heterogeneous precipitate nucleation positions which limited the strengthening phase precipitation in matrix and accelerated the precipitation along grain boundaries, resulted in fewer T₁ precipitates, coarse grain-boundary precipitates (GBPs), and wider precipitate-free zones (PFZs). The localized strain may be concentrated on the grain boundary to induce the dislocation pile-up, breaking of the GBPs, and intergranular fracture during stretching.     

Processing and characterization of the microstructure and mechanical properties of Al6061–TiB2 composite

In the present research, aluminum metal matrix composites were processed by the stir casting technique. The effects of TiB2 rein-forcement particles, severe plastic deformation through accumulative roll bonding (ARB), and aging treatment on the microstructural charac-teristics and mechanical properties were also evaluated. Uniaxial tensile tests and microhardness measurements were conducted, and the micro-structural characteristics were investigated. Notably, the important problems associated with cast samples, including nonuniformity of the rein-forcement particles and high porosity content, were solved through the ARB process. At the initial stage, particle-free zones, as well as particle clusters, were observed on the microstructure of the composite. However, after the ARB process, fracturing phenomena occurred in brittle ceramic particles, followed by breaking down of the fragments into fine particles as the number of rolling cycles increased. Subsequently, com-posites with a uniform distribution of particles were produced. Moreover, the tensile strength and microhardness of the ARB-processed com-posites increased with the increase in the reinforcement mass fraction. However, their ductility exhibited a different trend. With post-deforma-tion aging treatment (T6), the mechanical properties of composites were improved because of the formation of fine Mg2Si precipitates.     

Effect of rolling geometry on the mechanical properties,microstructure and recrystallization texture of Al–Mg–Si alloys

The effect of rolling geometry on mechanical properties, microstructure, and recrystallization texture of Al–Mg–Si alloys was studied by means of tensile tests, microstructural observations, and electron backscatter diffraction measurements. The results reveal that the elongation and the average plasticity strain ratio(r) values of the T4P(pre-aging plus natural aging)-treated alloy sheet with a rolling geometry value between 1 and 3 are somewhat higher than those of the T4P-treated sheet with a rolling geometry value between 3 and 6. The deformation and recrystallization microstructures of the sheet with a rolling geometry value between 1 and 3 are more uniform than those of the sheet with a rolling geometry value between 3 and 6. The former also possesses somewhat higher surface quality. H {001}110 and Goss {110}001 orientations are the main recrystallization texture components for the former case, whereas the latter case only includes H{001}110 orientation. Texture gradients are present in the two alloy sheets. Shear texture component F on the surface of the sheet with a rolling geometry value between 3 and 6 and its higher texture gradients have revealed that non-uniform deformation occurred during cold rolling. The effects of texture on the yield strength and r value were also discussed.     

Effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–Zn–Ca alloys

The effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–xZn–0.2Ca alloys (x=0.6wt%, 2.0wt%, 2.5wt%, hereafter denoted as 0.6Zn, 2.0Zn, and 2.5Zn alloys, respectively) are investigated. The results show that the Zn content not only influences grain refinement but also induces different phase precipitation behaviors. The as-cast microstructure of the 0.6Zn alloy is composed of α-Mg, Mg₂Ca, and Ca₂Mg₆Zn₃ phases, whereas 2.0Zn and 2.5Zn alloys only contain α-Mg and Ca₂Mg₆Zn₃ phases, as revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Moreover, with increasing Zn content, both the ultimate tensile strength (UTS) and the elongation to fracture first increase and then decrease. Among the three investigated alloys, the largest UTS (178 MPa) and the highest elongation to fracture (6.5%) are obtained for the 2.0Zn alloy. In addition, the corrosion rate increases with increasing Zn content. This paper provides an updated investigation of the alloy composition–microstructure–property relationships of different Zn-containing Mg–Zn–Ca alloys.     

Effects of sphere size on the microstructure and mechanical properties of ductile iron–steel hollow sphere syntactic foams

The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere (DI–SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder–binder suspension onto expanded polystyrene spheres (EPSs). Afterwards, the DI–SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy (SEM), and energy- dispersive X-ray spectroscopy (EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI–SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.     

Effect of cold rolling process on microstructure and mechanical properties of high strength β titanium alloy thin sheets

The microstructure and mechanical properties of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high strength titanium alloy sheets prepared by unidirectional cold rolling and two-step cross cold rolling were investigated. Results showed that the β phase grains were refined significantly by cold rolling followed by solution treatment for a short time.Compared to unidirectional cold rolling, the short time solution treatment after two-step cross rolling could significantly reduce the non-uniformity of the microstructure of the alloy sheets. After aging treatment at 550 ℃,the anisotropy of the mechanical properties still existed in the unidirectional rolled sheets, and the tensile strength was highest along the rolling direction. After solution and aging treatment, the anisotropy of the mechanical properties of the two-step cross rolling process sheet was not obvious than unidirectional cold rolling,and alloy had good strength and plasticity matching.     

Microstructure and properties of Cu–Ti–Ni alloys

The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu–3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu–3Ti–1Ni and Cu–3Ti–5Ni alloy was 300°C for 2 h and 450°C for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β′-Ni3 Ti and β′-Cu4 Ti precipitate from the Cu matrix during aging of the Cu–3Ti–5Ni alloy and that some residual Ni Ti phase remains. The increased electrical conductivity is ascribed to the formation of Ni Ti, β′-Ni3 Ti, and β′-Cu4 Ti phases.     

Effect of groove rolling on the microstructure and properties of Cu–Nb microcomposite wires

Cu–Nb microcomposite wire was successfully prepared by a groove rolling process. The effects of groove rolling on the diffraction peaks, microstructure, and properties of the Cu–Nb microcomposite were investigated and the microstructure evolutions and strengthening mechanism were discussed. The tensile strength of the Cu–Nb microcomposite wire with a diameter of 2.02 mm was greater than 1 GPa, and its conductivity reached 68% of the International Annealed Copper Standard, demonstrating the Cu–Nb microcomposite wire with high tensile strength and high conductivity after groove rolling. The results show that an appropriate groove rolling method can improve the performance of the Cu–Nb microcomposite wire.     

Effect of pickling processes on the microstructure and properties of electroless Ni–P coating on Mg–7.5Li–2Zn–1Y alloy

The electroless plating Ni–P is prepared on the surface of Mg–7.5Li–2Zn–1Y alloys with different pickling processes.The microstructure and properties of Ni–P coating are investigated.The results show that the Ni–P coatings deposited using the different pickling processes have a different high phosphorus content amorphous Ni–P solid solution structure,and the Ni–P coatings exhibit higher hardness.There is higher phosphorus content of Ni–P amorphous coating using 125 g/L Cr O3and 110 ml/L HNO3(w68%)than using 180 g/L Cr O3and 1 g/L KF during pre-treatment,and the coating structure is more compact,and the Ni–P coatings exhibit more excellent adhesion with substrate(Fcup to22 N).The corrosion potential of Ni–P coating is improved and exhibits good corrosion resistance.As a result,Mg-7.5Li-2Zn-1Y alloy is remarkably protected by the Ni–P coating.