Sc Addition Research Articles

Sc-containing hierarchical phase structures to improve the mechanical and corrosion resistant properties of Al-Mg-Si alloy

Although the effect of Sc addition on the nano-phase transformation of precipitates in Al-Mg-Si alloys has been evaluated in the literature, the properties and related explanation based on the multi-scale microstructures are less available yet. In this paper, the hierarchical microstructures and properties of peak-aging Al–0.5 Mg–0.4Si (wt.%) alloy (AlMgSi) and AlMgSi alloy microalloying with 0.4 wt% Sc (AlMgSiSc) were investigated by atomically-resolved transmission electron microscopy and atom probe tomography. The results show that a certain number of Sc solutes exist in the Al matrix, forming a solid solution strengthening matrix with reduced corrosion susceptibility. In addition, the strengthening and toughening of AlMgSiSc are associated with the formation of primary Al3Sc dispersoids, which cause dispersion strengthening and fine-grain strengthening. Moreover, the precipitate free zones (PFZs) containing Sc solutes were observed in the AlMgSiSc, leading to the excellent resistance to intergranular corrosion and elongation due to the smaller width and higher corrosion potentials of PFZ compared with AlMgSi. The Sc solutes can significantly promote the precipitation of GP zones and solute clusters. Further study reveals that smaller-scale precipitates, GP zones, and solute clusters have enrichment of Sc as well, thereby bringing out remarkable precipitation hardening to AlMgSiSc.

Effects of Sc on the microstructure and properties of in situ ZrB2/7085Al composites

The microstructure and mechanical properties of the ZrB2/7085Al composites containing Sc were studied. The ZrB2/7085Al composites were prepared by in situ reaction via Al-Zr-B system. On addition of Sc, it interacted with Zr present in the alloy resulting in the production of Al3(Sc, Zr) precipitates. Minor addition of Sc resulted in grain refinement, change in ZrB2 nanoparticles distribution, change in the size and morphology of the η phase and formation of Al3Sc and Al3(Sc, Zr) precipitates, which improved the strength significantly. The ultimate tensile strength (UTS), yield strength (YS) and elongation of 7085Al-ZrB2-Sc increased to 660.2, 603.4 MPa and 10.6%, respectively. These tensile properties improved 20.4%, 19.2% and 73.7%, respectively, over the 7085Al.

Study of Thermal Compression Constitutive Relation for 5182-Sc-Zr Alloy Based on Arrhenius-Type and ANN Model

Hot compression experiments were performed on alloy 5182 with small additions of Sc and Zr. The 5182 alloy containing Sc and Zr is critical for expanding the 5182 alloy’s range of applications, and a thorough understanding of its thermal processing behavior is of great importance to avoid processing defects. Alloy microstructure, including grain structures and Al3(ScxZr1−x) dispersoids were analyzed by EBSD and TEM. Stable flow stresses were observed below a strain rate of 1 s−1 for the Sc-Zr containing alloy. The results of constitutive models, with and without strain−compensation, and artificial neural network (ANN) were used to compare to the experimental results. The Al3(ScxZr1−x) dispersoid data was introduced into the ANN model as a nonlinear influence factor. Addition of the Al3(ScxZr1−x) dispersoid information as input data improved the accuracy and practicality of the artificial neural network in predicting the deformation behavior of the alloy. The squared correlation coefficients of ANN prediction data reached 0.99.

Fabrication and Sc-Refinement of SiCp/A356 Composites by Vacuum Stirring Casting Method

Aluminum matrix composites reinforced with 10 vol.% SiC particles (SiCp/Al MMCs) were prepared throughthe vacuum stirring method from SiC particles preoxidated at high temperature, followed by posttreatments of remelting and Sc addition treatment. Major problems during vacuum stirring preparation were investigated. Results show that overoxidation of SiC particles may occur during the vacuum stirring process, which causes loss of SiC particles and increases in “impurity pores” after solidification or aggregation of SiC particles, leading to scarcely improved mechanical properties of the prepared SiCp/Al composites. After Sc addition treatment, the α-Al and eutectic Si phases were obviously refined. The composite matrix was strengthened. The result indicates that the maximum tensile strength of 10 vol.% SiCp/A356 composites with Sc addition treatment was 193.5 MPa, which was increased by 43% compared with the matrix alloy. Moreover, a fracture at particles was detected after Sc addition treatment. The stress could be effectively transferred to the SiC particles when the fracture occurred.

Hot deformation behavior of Sc/Nb modified AA2195 Al–Li–Cu alloys

The hot workability of third generation AA2195 (Al–Li–Cu–Ag–Mg–Zr) alloy with different Sc (0.15–0.25 wt%) and Nb (0.15–0.25 wt%) additions in the homogenized condition was investigated using processing maps approach. The additions of Sc and Nb were found to be beneficial in refining the as-cast grain size of AA2195 and changing the morphology from less dendritic grain structure to a globular or equiaxed form. Hot compression tests carried out in the temperature, T, range of 300–450 °C and strain rate, ε˙, of 10−3 – 10 s−1 were utilized to generate processing maps at a true strain, ε = 0.5. The flow curves of the alloys exhibit a typical dynamic recovery (DRV) characteristics and Arrhenius type constitutive equations successfully predicted flow stress of the alloys. The results obtained from the processing maps and complementary microstructural analysis of the deformed specimens revealed that 0.15 wt% additions of Sc and Nb (separately or in combination) are optimum to improve its workability. However, increasing Sc and Nb contents to 0.25 wt% relatively expanded flow instability regions. With the aid of the processing maps, deformed specimens microstructural analysis, activation energy and Zener-Hollomon parameter, Domain D-3 occurring at higher temperatures and strain rates were identified as the “safe” regimes for hot working of AA2195 with optimum Sc and Nb contents (0.15 wt% added separately or in combination). Limited pancake type grain morphology with higher fractions of dynamically recrystallized (DRX) grains was observed in Domain D-3. The microstructural manifestation in the flow instability regions was flow localization (at higher strain rates), cavities formation at the grain boundaries & precipitates, particles breakage and wedge cracking at the triple junctions at lower strain rates.

The role of Sc on the microstructures and mechanical properties of the Ni-rich NiTi alloy

The microstructure and mechanical properties of Ni-rich alloys with the addition of Sc range from 0.15 at% to 0.5 at% were investigated by X-ray diffractometer(XRD), electro-probe microanalyzer(EPMA), transmission electron microscopy(TEM), microhardness, room-temperature tensile properties, and room-temperature fracture toughness in this paper. The as-cast binary alloy and Sc modified ternary alloy are mainly composed of NiTi matrix phase, Ni4Ti3, and Ni3Ti2 phases. After solution treatment, the Ni3Ti2 phase is dissolved back into the matrix, and the alloy mainly consists of NiTi matrix phase and nanoscale Ni4Ti3 phases. The addition of Sc inhibits the precipitation of brittle Ti2Ni phases because O is prone to combine with Sc to form Sc2O3. Trace Sc addition has a weak effect on the microhardness, and it can improve the room-temperature tensile properties and fracture toughness of the alloy. Trace Sc addition moderately reduce the size of the Ni4Ti3 phases and change the aspect ratio of the Ni4Ti3 phases. The reduced precipitate size is responsible for the improvement of alloy mechanical properties.

Effect of Minor Sc Addition on the Microstructure Evolution of Al–Cu–Li–Mg Alloy During Homogenization with Different Cooling Modes

Effect of Minor Sc Addition on the Microstructure Evolution of Al–Cu–Li–Mg Alloy During Homogenization with Different Cooling Modes

Ambient- and elevated temperature properties of Sc- and Zr-modified Al–6Ni alloys strengthened by Al3Ni microfibers and Al3(Sc,Zr) nanoprecipitates

The eutectic Al–6Ni (wt.%) alloy exhibits excellent strength at ambient and elevated temperature, provided by a high volume fraction of Al3Ni microfibers formed during solidification. Here, Al–6Ni is micro-alloyed with Sc and Zr (with 0.1Sc+0.2Zr, 0.2Sc+0.4Zr and 0.3Sc+0.2Zr, wt.%), creating two additional populations of primary and secondary Al3(Sc,Zr) precipitates. The fully eutectic microstructure (α-Al + Al3Ni) observed in Al–6Ni alloy changes, with Sc and Zr addition to hypoeutectic microstructure with primary α-Al grains nucleated on solidification by primary Al3(Sc,Zr) precipitates. Upon subsequent aging, fully-coherent Al3(Sc,Zr) nanoprecipitates form in the α-Al matrix between Al3Ni microfibers, providing substantial precipitation strengthening, which is maintained for up to 1 month at 350 °C. Alloy strength - both at ambient temperature and during creep at 300 °C - can be quantitatively described through a superposition of precipitation strengthening by Al3(Sc,Zr) nanoprecipitates and load-transfer strengthening by Al3Ni microfibers.

Elimination of extraordinarily high cracking susceptibility of aluminum alloy fabricated by laser powder bed fusion

Using the calculation of phase diagrams approach and Scheil solidification modeling, the Al-2.5Mg-1.0Ni-0.4Sc-0.1Zr alloy was designed, intentionally with an extraordinarily high cracking susceptibility, making it prime for solidification cracking during laser powder bed fusion. This study demonstrates the ability to mitigate even the most extreme solidification cracking tendencies in aluminum alloys with only minor alloying additions of Sc and Zr, 0.5 wt.% max. Furthermore, by employing a simple direct ageing heat treatment, good tensile mechanical properties were observed with a yield strength of 308 MPa, an ultimate tensile strength of 390 MPa, and a total elongation of 11%.

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

Effects of Sc and Zr addition on the solidification and mechanical properties of Al–Fe alloys

The effects of Sc and Zr on the microstructure and properties of Al–3Fe alloys were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and mechanical property testing. The results show that the Al 3 (Sc, Zr) phases with a L1 2 structure are formed with the addition of Sc and Zr, which promotes the heterogeneous nucleation, reduces the segregation and improve columnar grains. In the process of iron-rich phase nucleation and growth, Sc and Zr atoms are adsorbed around iron-rich phases, which prevents the growth of iron-rich intermetallics and makes the needle-like primary Al 3 Fe phases gradually change to short rod-like, butterfly-like and flower-like morphologies. Additionally, the fibrous eutectic Al 6 Fe phases are also observed. With increasing the Sc and Zr contents from 0 to 0.35 wt% and 0 to 0.14 wt%, respectively, the strength of the alloy increases and the elongation decreases. The Al–3Fe alloy with the addition of 0.16 wt% Sc and 0.06 wt% Zr has a tensile strength of 160.8 MPa and a yield strength of 132.4 MPa. During aging process, fine, dispersed and coherent nanoscale secondary Al 3 (Sc, Zr) (L1 2 structure) phases are formed in the α-Al matrix to promote precipitation strengthening. When the addition of Sc and Zr is 0.35 wt% and 0.14 wt%, respectively, the refinement effect on the macrostructure and the second phase is most obvious. After aging, the tensile strength reaches 233 MPa and the yield strength reaches 200 MPa.

The influence of Sc and Zr additions on microstructure and corrosion behavior of AA5182 alloy sheet

Minor additions of Sc and Zr to a 5182 base alloy were used to study the effects of microstructure on the susceptibility to intergranular corrosion (IGC) of 5xxx sheet alloys. The results showed that minor Sc and Zr additions significantly decrease the IGC susceptibility as measured by the depth of IGC for the high-temperature annealed sheet. The improvement in IGC resistance is attributed to a high number density of nano-scaled coherent Al3(Sc,Zr) dispersoids which resist recrystallization, and produce a fine subgrain structure. The character of the subgrain structure is critical to prevent the occurrence of continuous intergranular Al3Mg2 precipitates during sensitization.

Features of the Microstructural Composition of Low-Alloyed Aluminum Alloys of the 6XXX Series with Small Additions of Zr and Sc

The study investigates the effect of Zr and Sc on the dendritic structure and phase composition during casting of a silicon rich Al0.3Mg1.0Si alloy. Optical microscopy, computations using Thermo-Calc software and electron microscopy were applied. It showed that scandium and zirconium additions facilitate dendritic structure refinement, however, the maximum effect is achieved by their combined addition. Computations demonstrated the occurance of three main phases in case of Sc (without zirconium) addition to Al0.3Mg1.0Si alloy: i) the strengthening Mg2Si phase, ii) the harmful ScSi phase and iii) free silicon. In case of only Zr addition, the same phases are observed, except for ScSi replaced with Zr2Si, which has not been studied in Al-Mg-Si alloys. Computations predict the occurance of all three phases in the case of the combined Sc and Zr addition, besides, strengthening Al3(ScZr) can be expected. Electron microscopy shows, that all alloys contain Mg2Si phases as well as Al12Fe3Si and Al9Fe2Si2 type phases, formed due to the iron impurity. The main Zr and Sc fractions occur in solid solution, thus, a quenching rate of 1 oС/s is sufficient to achieve a self-hardening effect.

Effects of Sc Addition and Retrogression and Re-aging on Microstructure and Mechanical Properties of Al-8Zn-2Mg-2Cu-0.15Zr Alloy

Effects of Sc Addition and Retrogression and Re-aging on Microstructure and Mechanical Properties of Al-8Zn-2Mg-2Cu-0.15Zr Alloy

Microstructures and corrosion behaviors of Al–6.5Si–0.45Mg–xSc casting alloy

The microstructures and corrosion behaviors of the Al–6.5Si–0.45Mg casting alloys with the addition of Sc were investigated by using scanning electron microscopy, X-ray diffraction, electrochemical measurement techniques and immersion corrosion tests and compared with those of Sr-modified alloy. The results show that Sc has evident refining and modifying effects on the primary α(Al) and the eutectic Si phase of the alloy, and the effects can be enhanced with the increase of Sc content. When the Sc content is increased to 0.58 wt.%, its modifying effect on the eutectic Si is almost same as that of Sr. Sc can improve the corrosion resistance of the test alloy in NaCl solution when compared with Sr, but the excessively high Sc content cannot further increase the corrosion resistance of the alloy. The corrosion of the alloys mainly occurs in the eutectic region of the alloy, and mostly the eutectic α(Al) is dissolved. This confirms that Si phase is more noble than α(Al) phase, and the galvanic couplings can be formed between the eutectic Si and α(Al) phases.

The Effect of Scandium on the Structure, Microstructure and Superconductivity of Equimolar Sc-Hf-Nb-Ta-Ti-Zr Refractory High-Entropy Alloys.

In this study, we investigate the scandium-containing Sc-Hf-Nb-Ta-Ti-Zr system of refractory high-entropy alloys (HEAs). Using the arc-melting method, we synthesized nine equimolar alloys (five 4-, three 5- and one 6-component), with all of them containing Sc. The alloys were characterized by XRD, electron microscopy and EDS, while superconductivity was investigated via electrical resistivity, specific heat and the Meissner effect. The results were compared to the parent Hf-Nb-Ta-Ti-Zr refractory HEAs, forming a single-phase body-centered cubic (bcc) structure and quite homogeneous microstructure. The addition of Sc produces a two-phase structure in the Sc-Hf-Nb-Ta-Ti-Zr alloys, with one phase being bcc and the other hexagonal close-packed (hcp). The hcp phase absorbs practically all Sc, whereas the Sc-poor bcc phase is identical to the bcc phase in the Hf-Nb-Ta-Ti-Zr parent system. Upon the Sc addition, the microstructure becomes very inhomogeneous. Large bcc dendrites (10–100 µm) are homogeneous in the central parts, but become a fine dispersion of sub-micron precipitates of the bcc and hcp phases close to the edges. The interdendritic regions are also a fine dispersion of the two phases. Superconductivity of the Sc-Hf-Nb-Ta-Ti-Zr alloys originates from the bcc phase fraction, which demonstrates identical superconducting parameters as the bcc Hf-Nb-Ta-Ti-Zr parent alloys, while the Sc-containing hcp phase fraction is non-superconducting.

Improving mechanical properties of Al–Si–Cu–Mg alloys by microallying Sc using thermodynamic calculations

The mechanical properties of Al–Si–Mg alloys are largely related to eutectic Si, intermetallics and pores. In this study, the effects of the Sc addition on the eutectic Si, Sc containing precipitates and pores were investigated, and the mechanical properties of the alloy were improved by adding Sc. The Sc addition leads to the formation of Al3M (M = Sc, Zr, Ti,V) and reduction of pore size, increasing the yield strength (YTS), ultimate tensile strength (UTS) and elongation (EL) of the alloy after the T6 heat treatment. The formation of thermally stable Al3M (M = Sc, Zr, Ti,V) after the T6 heat treatment improves the elevated temperature strength.

Heat-Resistant Al-Alloys with Quasicrystalline and L1<sub>2</sub>- Precipitates

We have been developing Al-Mn-Cu based alloys alloyed with minor additions of different elements. Small additions of beryllium enhance the formation of the icosahedral quasicrystalline phase (IQC) during solidification, especially during ageing. Upon solidification, primary IQC-particles may form, with sizes, ranging from 5 to 50 μm. IQC is also present as a part of binary eutectic in the interdendritic regions. More importantly, nanosized quasicrystalline precipitates can form during T5-treatment at temperatures ranging from about 250−450 °C. They are, in fact, metastable precipitates transforming to ternary T-precipitates (Al20Mn3Cu2) phase above 450 °C. The heat resistance can be increased considerably by the addition of Sc and Zr by forming L12-precipitates in spaces between quasicrystalline precipitates. In this paper, we studied three alloys, two Al-Mn-Cu-Be alloys and an Al-Mn-Cu-Be-Sc-Zr alloy. The alloys were produced by vacuum induction melting and casting into a copper mould. We investigated the response of the alloys to different heat treatments and their heat resistance at higher temperatures. It was shown that the alloys could be precipitation strengthened by ageing at 300 °C and 400 °C. The hardness of the alloy stayed at relatively high levels even at 500 °C, while more substantial softening occurred at 600 °C.

Synergistic Effect of Mn+Sc Additions on the Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Mn-Sc Alloy

Synergistic Effect of Mn+Sc Additions on the Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Mn-Sc Alloy

Synergistic Effect of Mn+Sc Additions on the Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Mn-Sc Alloy

Synergistic Effect of Mn+Sc Additions on the Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Mn-Sc Alloy