Effect of Trace Sc and Zr on the Mechanical Properties and Microstructure of A1 Alloy 2618

An experimental 2618(Al-Cu-Mg-Fe-Ni) alloy added with trace Sc and Zr was prepared by ingot metallurgy (IM) method. The aging behavior of the alloy was studied by Vickers hardness measurement at 200℃ and 300℃. and the tensile properties of alloy specimens were measured at 20℃, 200℃, 250℃ and 300℃. The microstructure was observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a primary Al_3(Sc,Zr) phase which could refine the grain because it acts as nuclei of heterogeneous crystallization in the melt during solidification. The secondary Al_3(Sc,Zr) particles were full coherent with matrix and had obvious precipitation hardening effect. They also made the S' phase precipitate more homogeneous. So the strength of alloy increases at both ambient and elevated temperatures without a decrease of ductility. The ductile fracture of alloy occurs by microvoid nucleation, growth and coalescence, so the microvoid coalescence is the dominant fracture mechanism.

Effect of minor Sc and Zr on microstructures and mechanical properties of Al-Zn-Mg based alloys

Two kinds of Al Zn Mg based alloys with and without Sc, Zr addition were prepared by ingot metallurgy. The tensile mechanical properties and microstructures of the studied alloys at different treatment conditions were studied. The results show that addition of minor Sc and Zr can remarkably improve the strength of Al Zn Mg based alloys, but the ductility remains on a higher level. The strength increment is mainly due to fine grain strengthening, substructure strengthening and precipitation strengthening of Al 3(Sc,Zr).

Microstructures evolution and mechanical properties disparity in 2070 Al-Li alloy with minor Sc addition

The microstructures and mechanical properties of Al-3.35Cu-1.2Li-0.4Mg-0.4Zn-0.3Mn-0.1Zr （mass fraction, %） alloywith Sc addition or free Sc were investigated through tensile test, SEM, EPMA and TEM. The addition of 0.082% （mass fraction） Scelement leads to the formation of Cu-rich and Sc-contained nano-sized Al3（ScZr） particles and W phase particles. The Al3（ScZr）particles can inhibit recrystallization to a certain extent and impede recrystallized grain growth during solution treatment. It is foundthat W phase cannot dissolve in supersaturated solid solution during the solution heat treatment, and the Cu content in thesolutionized matrix is decreased, which causes a decrease in the fraction of Cu-contained strengthening precipitates with T1 （Al2CuLi）and θ＇ （Al2Cu） under T8 aging condition. Due to the formation of the W phases, the small Sc addition causes a little reduction in thestrength.

Microstructure and mechanical properties of Al-5.8Mg-Mn-Sc-Zr alloy after annealing treatment

An A1-5.8Mg-0.4Mn-0.35（Sc＋Zr） （mass fraction, %） alloy sheet was prepared using water chilling copper mould ingot metallurgy processing which was protected by active flux. The influence of stabilizing annealing on mechanical properties and microstructure of the cold rolling sheet was studied. The results show that the strength and hardness of the alloy decrease, while the elongation increases with increasing the stabilizing annealing temperature. With the increase of stabilizing annealing time, the strength and hardness of the alloy drop slightly but its ductility exhibits no change. Partial recovery and recrystallization orderly occur with the increase of annealing temperature during stabilizing treatment. Only different degrees of recovery occur in the alloys annealed below 400 ℃ for 1 h. Partial recrystallization occurs after annealed at 450 ℃ for 1 h. By annealing at 300 ℃ for 1 h, the alloy can obtain the optimum application values of δb, δ0.2 and δ, which are 436 MPa, 327 MPa and 16.7%, respectively.

Effect of Sc and Zr on microstructures and mechanical properties of as-cast Al-Mg-Si-Mn alloys

Microstructures of as-cast Al-Mg-Si-Mn alloys with and without Sc and Zr were investigated by optical microscopy, scanning electronic microscopy(SEM) and energy dispersion spectrum analysis. Addition of 0.2%-0.4% Sc can refine the grain size and change the growth morphology from dendritic to fine equi-axial crystal. The higher the addition of Sc, the finer the as-cast grain size. The tensile strength is increased by more than 30% with 0.4% Sc. Moreover, an addition of 0.1%-0.2% Zr is able to refine grain size and change the growth morphology from dendritic to equi-axial grain too, but less effective. However, Zr is found to increase the ductility of the cast alloys, and the elongation is increased to 11.97% with 0.2% Zr.

Microstructures and mechanical properties of Al-Mg and Al-Zn-Mg based alloys containing minor scandium and zirconium

A series of Al Mg and Al Zn Mg based alloys with and without Sc, Zr were prepared by ingot metallurgy. The mechanical properties and microstructures of the studied alloys under different treatment conditions were studied. In addition, the existing form and acting mechanism of minor Sc and Zr in Al Mg and Al Zn Mg based alloys were analyzed and discussed. The following conclusions can be drawn. First, adding of minor Sc and Zr to those alloys can increase the strength of Al Mg and Al Zn Mg based alloys by 25%, while the ductility can remain in 15% and 8%, respectively. Second, in Al Mg and Al Zn Mg based alloys, minor Sc and Zr mainly exist in two forms of aluminides containing Sc and Zr, one is Al 3(Sc,Zr) I precipitated from the melt during solidification, the other is Al 3(Sc,Zr) Ⅱ precipitated during homogenization. The former is the most effective grain refiner for α (Al) solid solution matrix, and the latter is coherent with the matrix and can strongly pin dislocations and subboundaries, which can effectively restrain recrystallization of the alloys during hot deformation, annealing and solid solution. Third, strengthening caused by adding minor Sc and Zr to the studied alloys is mainly due to fine grain strengthening, precipitation strengthening and substructure strengthening of Al 3(Sc, Zr) caused by restraining recrystallization.

Effect of Rare Earth Sc Addition on Microstructure and Mechanical Properties of an Al-Cu-Mg-Ag Alloy

Al-5.3Cu-0.8Mg-0.6Ag alloys containing 0, 0.1, 0.3 and 0.5 (mass. %) Sc were prepared by ingot metallurgy and thermomechanical treatment. The effect of Sc addition on the precipitation and microstructure of the alloys has been investigated using mechanical testing, optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been shown that trace Sc element refines the grains of the casting alloys and the average grain size decreases from 85 μm to 30 μm. Increasing Sc content from 0.1 to 0.3% accelerates the aging hardening process, increases the maximum hardness and the tensile strength of the extruded alloys from room temperature to 300 ℃. The high strength of the alloys with Sc is attributed to the high density and high thermal stability of fine Ω precipitates, and nanosized Al3(Sc,Zr) and AlCu(Zr, Sc) particles.

Effects of micro-alloying with Sc and Mn on microstructure and mechanical properties of Al-Mg based alloys

An extensive investigation was made on the effects of micro-alloying with small amounts of Sc and Mn on the microstructure and mechanical properties of the Al-Mg based alloys. It is found that the micro-alloying can significantly enhance the tensile strength of the alloys, and eliminate the dendritic cast structure in it. Many fine, spherical and dispersive Al3Sc particles are found in the annealed Al-Mg-Mn-Sc alloys, which can strongly pin up dislocations and subgrain boundaries, thus strongly retarding the recrystallization of the alloys. The strengthening of the micro-alloyed Al-Mg alloys is attributed to the precipitation strengthening by the Al3Sc particles and to the substructure strengthening.

Effects of Sc and Mn on microstructures and mechanical properties of Mg-Gd alloy

Two alloys of Mg-12.4Gd and Mg-12.5Gd-0.8Sc-1.4Mn were prepared. Hot extrusion and T5 heat treatment were conducted,and then the mechanical properties of the two alloys were tested at room and high temperatures. The effects of Sc,Mn on the microstructures of Mg-12.4Gd were investigated by optical microscopy,scanning electron microscopy and transmission electron microscopy. The results demonstrate that after hot-extrusion the alloying with Sc,Mn can efficaciously refine the grains of Mg-12.4Gd alloy;and increase the elongation at room and high temperatures after T5 heat treatment. But the strength at high temperature is not obviously improved.

Effects of cold rolling and heat treatment on microstructure and mechanical properties of AA 5052 aluminum alloy

The microstructures and mechanical properties of homogenized-rolled AA5052 aluminum alloys with different rolling reductions and following annealing treatments were investigated by optical microscope, scanning electron microscope, X-ray diffractometer, micro-hardness and tensile tests. The results show that with increasing rolling reduction, the equiaxed grains are elongated along the rolling direction obviously, and accumulation of rolling reduction increases the work hardening effect, which results in the enhanced strength and degraded plasticity. When rolling reduction is 87%, the ultimate tensile strength reaches 325 MPa but elongation is only 2.5%. There are much more secondary phase precipitates after annealing treatment. With an increase of annealing temperature, the amount of precipitates increases and work hardening diminishes continuously. The elongation is improved to ~23% but the tensile strength is decreased to 212 MPa after annealing at 300 °C for 4 h, which are comparable to those of as-homogenized alloy.

Effects of non-isothermal annealing on microstructure and mechanical properties of severely deformed 2024 aluminum alloy

Microstructure and mechanical properties of AA2024 after severe plastic deformation （SPD） and non-isothermal annealing were investigated. The non-isothermal treatment was carried out on the severely deformed AA2024, and the interaction between restoration and precipitation phenomena was investigated. Differential scanning calorimetry, hardness and shear punch tests illustrate that static recovery and dissolution of GPB zones/Cu-Mg co-clusters occur concurrently through non-isothermal annealing. Scanning electron microscope and electron backscatter diffraction illustrate that non-isothermal annealing of deformed AA2024 up to 250 ℃ promotes the particle-free regions and also particle stimulated nucleation. Results show that through heating with the rate of 10 ℃/min up to 250 ℃, the ultimate shear strength and the hardness are maximum due to the presence of S＇/S phases which have been detected during non-isothermal differential scanning calorimetry experiment. Also, recrystallization phenomenon occurs in temperature range which includes the dissolution of S＇/S phases. The concurrent recrystallization and dissolution of S＇/S phase at 380 ℃ have been verified by differential scanning calorimetry, mechanical properties, and optical microscope.

Microstructure and mechanical properties of friction stir welded AA7075-T651 aluminum alloy thick plates

Friction stir butt welding of AA7075-T651 plates with thicknesses of 10 and 16 mm was investigated. Defect-free, full- penetration welds were obtained after careful process parameter selection. While the nuggets in both welds exhibited very fine reerystallized grains, and finer grains were observed in welds made on 10 mm thick plates. Microhardness surveys revealed that significant loss in hardness occurs in the heat-affected zone. The reduction in hardness due to the welding process is higher in the case of welds made on 16 mm thick plates. Welds made on 10 mm thick plates exhibited superior tensile properties compared with those made on 16 mm thick plates. Fracture during tensile test occurred in the heat-affected zone in both cases. TEM images of specimens revealed that the heat-affected zone consisted of widened precipitate-free zones along grain boundaries and partial dissolution of precipitates in the grain interiors. It is concluded that defect-free single pass welds can be made on AA7075-T651 thick plates using friction stir welding and the welds made on 10 mm thick plates exhibit high joint efficiency.

Relationship among Mechanical Properties Anisotropy,Microstructure and Texture in AA 6111 Alloy Sheets

We comparatively studied the mechanical properties anisotropy, microstructure and texture of the commercial and the new developed AA6111 alloys through tensile test, optical microscopy, and XRD analysis. The results show that the anisotropy of mechanical properties for the developed AA6111 alloy is lower than that of the commercial alloy. The developed alloy possesses higher r value, lower Ar value and more uniform microstructure, compared with the commercial AA6111 alloy, indicating that the deep drawability of the developed alloy has been improved significantly. The recrystallization textures of the two alloy sheets are also different. The recrystallization texture of the commercial alloy sheet mainly includes Cube and { 114}〈311〉 orientations, while the recrystallization texture of developed alloy sheet consists of Cube, Goss and R orientations. The relationships among the deep drawabilities, microstructure and texture were discussed thereafter.

Effects of Sc Addition and Annealing Treatment on the Microstructure and Mechanical Properties of the As-rolled Mg-3Li alloy

The microstructures and mechanical properties of the as-rolled Mg-3Li and Mg-3Li-1Sc （wt%） alloys before and after annealing treatment have been investigated. Results show that the grains are refined evidently and the recrystallization temperature is improved for more than 100℃by adding 1 wt% Sc into the Mg-3Li alloy. After complete recrystallization, both the strength and ductility of the Mg-3Li alloy are improved evidently with the addition of minor Sc. The brittle fracture tendency of Mg-3Li-ISc alloy also reduces obviously.

Effects of heat input in friction stir welding on microstructure and mechanical properties of AA3003-H18 plates

The non-heat-treatable AA3003-H18 plates were joined by friction stir welding（FSW） to achieve a proper joint by optimizing the welding parameters.For this purpose,the effects of heat input on microstructure and mechanical properties of the welded samples were investigated by changing the ratios of rotational speed（800-1200 r/min） to travel speed（40-100 mm/min）（w/v）.It was revealed that the grain growth rate was strongly increased with the increase of the heat input by rotational speed at constant travel speed,while the grain growth rate was slightly increased with the increase of the heat input by travel speed at constant rotational speed.Subsequently,hardness reduction was observed in the stir zone at higher rotational speed compared with that at lower one.An interesting observation was that various welding parameters do not have noticeable effect on the tensile strength of the FSW joints.Also,it has been observed that the fracture location of tensile test specimens was placed in the heat-affected zone（HAZ）on the advancing side at lower travel speed,while at higher travel speed,it was placed at the HAZ/thermomechanical affected zone（TMAZ） interface on the retreating side.

Microstructure and properties of Al-4 Cu alloy containing Sc

The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experimental results show that rare earth element Sc is capable of refining the dendritic structure of the Al 4%Cu alloy, the tensile strength σ b and yield strength σ 0.2 just increase a little when the content of Sc is lower than 0.2%; when the content reaches 0.3%0.4%, σ b and σ 0.2 slightly decrease; but σ b and σ 0.2 rise again when the Sc content is 0.5%, though both of them are lower than those of the Al 4%Cu alloy without Sc addition. However, Sc addition has little influence on the elongation of the Al 4%Cu alloy. Adding Sc to the Al 4%Cu alloy, when the amount of Sc is lower than 0.2%, Sc mostly exists in the α (Al) solid solution; when the Sc content is in the range of 0.3%0.5%, only a part of Sc exists in the α Al solid solution, the rest appears in two ways: one is that Sc and Al form Al 3Sc which can strengthen the alloy, and the other, Sc interacts with Al and Cu to form AlCuSc phase.

Effects of in-situZrB_2 nanoparticles and scandium on microstructure and mechanical property of 7N01 aluminum alloy

In this study, the in-situ synthesized ZrB_(2) nanoparticles and rare earth Sc were introduced to enhance the strength and ductility of 7N01 aluminum alloy, via the generation of high-melting and uniform nanodispersoids. The microstructure and mechanical property evolution of the prepared composites and the interaction between ZrB_(2) and Sc were studied in detail. The microstructure investigation shows that the introduction of rare earth scandium(Sc) can promote the distribution of ZrB_(2) nanoparticles, by improving their wettability to the Al melt. Meanwhile, the addition of rare earth Sc also modifies the coarse Al Zn Mg Mn Fe precipitated phases, refines the matrix grains and generates high-melting Al_3(Sc,Zr)/Al_3Sc nanodispersoids. Tensile tests of the composites show that with the combinatorial introduction of ZrB_(2) and Sc, the strength and ductility of the composites are improved simultaneously compared with the corresponding 7N01 alloy, ZrB_(2) /7N01 composite and Sc/7N01 alloy. And the optimum contents of ZrB_(2) and Sc are 3 wt% and 0.2 wt% in this study. The yield strength, ultimate strength and elongation of(3 wt% ZrB_(2) +0.2 wt% Sc)/7N01 composite are 477 MPa, 506 MPa and 9.8%, increased about 18.1%, 12.2%and 38% compared to 7N01 alloy. Furthermore, the cooperation strengthening mechanisms of ZrB_(2) and Sc are also discussed.

Effect of TiB_(2)Addition on Microstructure and Mechanical Properties of AA8009 Alloy Fabricated by Laser Additive Manufacturing

The research involves the addition of 5 vol.%TiB_(2)particles into AA8009 alloy powder to synthesize TiB_(2)/AA8009 composite parts produced via laser powder bed fusion(LPBF).The addition of the TiB_(2)particles causes the TiB_(2)/AA8009 composites with and without annealing have lower compressive strength than AA8009 alloy due to the change of the strengthening mechanism.The results further indicated that solid solution strengthening was the main strengthening mechanism of the LPBF AA8009 alloy at room temperature whereas Orowan strengthening became the primary strengthening factor after annealing at 673 K.In contrast,Orowan strengthening always remained the main strengthening mechanism for the TiB_(2)/AA8009 composite,irrespective of the annealing temperature.In addition,after annealing of the LPBF parts at 673 K,the compressive yield strength(CYS)of the unblended AA8009 alloy specimens had a~2.5 times greater reduction(from 705±16 to 459±30 MPa)compared to that of the composite TiB_(2)/AA8009 samples(from 466±23 to 368±3 MPa).Therefore,TiB_(2)particles can suppress the drop in yield strength of LPBF AA8009 alloy below 673 K,providing a theoretical and experimental basis for the applications of both LPBF AA8009 and TiB_(2)/AA8009 alloys at low and medium temperatures.

Microstructure, Texture, Mechanical and Ballistic Properties Correlation of a Hot Rolled and Peak Aged AA-7017 Alloy Plate at Surface and Centre

The present work describes microstructure, texture, mechanical and ballistic properties correlation of a hot rolled and peak aged AA-7017 alloy plate at surface and centre. Both the microstructures and textures are different on the surface and centre of the plate. The surface of the plate shows recrystallized grains and a weak over all texture. The centre of the plate displays elongated grains and a sharp texture. Tensile properties, hardness and impact toughness are evaluated at surface and centre of the plate. It is observed that strength and hardness is high at centre, whereas ductility and impact toughness is more at the surface. Ballistic properties of the plate at centre and surface are measured by impacting against two different 7.62 mm deformable projectiles. The plates impacted on the surface shows better ballistic resistance. Ballistic performance of the plate at surface and centre has been correlated with the microstructure, texture and mechanical properties.

Mechanical properties and thermal stability of 7055 Al alloy by minor Sc addition

This study investigated the effect of 0.25 wt%Sc addition on the microstructure and mechanical properties of AA 7055 alloy.The addition of Sc obviously refined the grains of AA 7055 alloy during casting,homogenizing,rolling,solution,and aging treatments due to the formation of primary and precipitate Al3(Sc,Zr)phase.The recrystallization and precipitation of AA 7055 alloy were inhibited during heat treatments by Sc addition.The Sccontaining AA 7055 alloy exhibited higher thermal stability than AA 7055 alloy during homogenizing treatment,because of the grain boundary pinning effect of nano-sized Al3(Sc,Zr)particles.Given its structure characteristics such as fine grains,fineη′phase,and lessηphase,AA 7055 alloy with added Sc showed good mechanical properties after aging at 120℃for 24 h,with an ultimate tensile strength(UTS)of 679 MPa and elongation(EL)of 14%.This work provides an effective strategy to fabricate AlZn-Mg(-Cu)series(7 xxx)alloys with excellent mechanical properties.