Microstructure and tensile properties of FeMnNiCuCoSnx high entropy alloys

High-entropy FeMnNiCuCoSn_x (x denotes the atomic fraction of Sn) alloys with good plasticity have been developed. The systematical investigation demonstrates that the concentration of Sn element plays a significant role in the microstructure and tensile properties. As 0.03 < x < 0.05, the alloys exhibit high tensile strength and plasticity, and the maximum elongation strain and strength are 16.9% and 476.9 MPa, respectively, because of their single FCC solutions. While the concentration of Sn is higher than 0.05, an intermetallic compound (Cu_5.6Sn) in the interdendritic regions forms, which degrades the ductility of alloys.     

Casting defects and the tensile properties of an AlSiMg alloy

Samples containing either entrapped dross and oxide films, gas porosity or small drilled holes have been used to study the effect of different types of defects on the tensile behaviour of an Al7Si0.4Mg casting alloy. The tensile properties show little or no correlation with the bulk porosity content, especially in the case of samples containing dross and oxide films. In contrast, the decrease in tensile ductility and strength correlates with the area fraction of defects in the fracture surface of the samples. The experimental results are in agreement with the predictions of a simple analysis based on models for the growth of a plastic instability in a tensile sample.     

Microstructure and tensile properties of Ni3 (Si,Ti) alloys containing second phase dispersions

Abstract

The alloying behaviour, microstructure, and high temperature mechanical properties of quaternary polycrystalline Ni₃ (Si,Ti), which was alloyed with transition elements V, Nb, Zr, and Hf beyond their maximum solubility limits, were investigated. The solubility limits of the quaternary elements in the L1₂ Ni₃ (Si,Ti) phase were determined to be ranked in the sequence of Nb > V > Hf > Zr, and correlated with the size misfit parameter between Si and the quaternary element X, and with the difference in formation enthalpy between Ni₃ Si and Ni₃ X. The second phases (dispersions) formed beyond the solubility limit were identified as a face centred cubic type Ni solid solution for the V containing Ni₃ (Si,Ti) alloy and Ni₃ X type compounds of the Nb, Zr, and Hf containing Ni₃ (Si,Ti) alloys. The second phase dispersions in the L1₂ phase matrix resulted in strengthening over a wide range of temperatures. The high temperature tensile elongation was improved by the introduction of the second phase dispersions. Among the quaternary Ni₃ (Si,Ti) alloys observed in the present study, the Nb containing Ni₃ (Si,Ti) alloy with the Nb containing second phase dispersion was shown to have the most favourable mechanical properties.     

Microstructure and properties of melt-quenched TiNi-based alloys

Titanium-nickel (TiNi) based alloys doped with hafnium and copper have been obtained by melt-jet spinning at a cooling rate of 10⁵–10⁶ K/s. The melt-spun ribbons have been studied by the electron — microscopy and X-ray diffraction techniques. It is established that, depending on the content of doping elements and cooling rate, the alloys occurred in an either amorphous or mixed amorphous-crystalline state. Mechanical properties of the obtained alloys have been measured.     

Microstructure and properties of burn-resistant Ti-Al-Cu alloys

Ti-Al-Cu series burn-resistant alloys are newly developed materials which have low density, low cost and are easy to process. The results show that Ti-Al-Cu alloys have good burn resistance due to their good thermal conductivity, low melting point, and the existence of Ti₂Cu phase which also has a very low melting point. Ti-Al-Cu alloys have excellent thermal processability and good room and high temperature tensile properties, but an increase in copper content harms their thermal stability. After thermal exposure for a long time, Ti₂Cu phase will coalesce and coarsen, but the addition of Si and Al will be useful for their thermal stability. The Ti-13Cu-1Al-0.2Si alloy has good thermal stability at 540°C and good creep resistance at 300°C and 100 MPa. The phases of Ti-Al-Cu alloys were found to be composed of phase and Ti₂Cu. The character of the Ti₂Cu phase changes with the increasing copper content.     

Microstructures and tensile properties of spray-deposited high-strength aluminium alloys

Spray deposition is a new rapid solidification technique which produces bulk preforms directly from the melt metals. A spray deposition process was used to develop several high-strength aluminium alloys based on their commercial chemical compositions. These alloys include 2024 alloy, 7075 alloy and 7075 alloy modified with 1.0% Fe and 1.0% Ni.The deposits possessed rapid solidification microstructure with grain size of about 20 μm and a relative density of over 94%. The hardening phases of the materials in T4 or T6 conditions consisted of supersatured solid solution, stable and unstable ageing precipitates and disperse phases. The formation of the fine distributed disperse phases was due to the addition of iron and nickel to the 7075 alloy. The spray-deposited materials exhibited substantial improvement in tensile strengths and maintained acceptable ductility when compared to the corresponding ingot metallurgy processed materials. This revised version was published online in November 2006 with corrections to the Cover Date.     

Subzero tensile properties of vapour quenched aluminium alloys

Supersaturated and metastable aluminium alloy solid solutions containing a dispersed phase have been produced by a vapour quenching technique. Binary alloys contained 3.5% Fe and 5.5% Mn; ternary alloys contained 6 to 9% chromium and 0.5 to 1.2% iron. After rolling into sheet the tensile properties were determined in the temperature range 293 to 77 K. At 77 K tensile strengths of 1115 and 1036 MPa were obtained for two Al-Cr-Fe alloys, equivalent to E/82 and E/83, respectively. These are the highest strengths ever reported for an aluminium alloy. The deformation behaviour at subzero temperatures has indicated the potential for further strengthening of metastable rapidly solidified aluminium alloys by dislocations alone.     

原位生成(TiBw+TiCp)/Ti复合材料的高应变速率超塑性

将纯钛粉和B4C粉按一定比例混合均匀后,通过反应热压方法原位合成制备了TiB晶须和TiC颗粒增强体积分数为3%的钛基复合材料,并在950℃以16∶1的挤压比对复合材料进行了高温热挤压变形.采用X射线衍射仪和扫描电镜分别研究了原位生成复合材料的相结构和微观组织,并在700℃以不同应变速率对钛基复合材料进行了高温拉伸变形.研究表明:纯钛和B4C在1200℃真空热压原位合成产生两种不同形状的增强体,即短纤维状TiB晶须和等轴状的TiC颗粒;应变速率为5.95×10-4、1.19×10-3s-1和0.89×10-2s-1时,(TiBw TiCp)/Ti复合材料都表现出超塑性,延伸率分别为205.43%、148.3%和112.85%;700℃变形时(TiBw TiCp)/Ti复合材料的应变速率敏感指数为0.45.     

Elevated temperature tensile properties of squeeze-cast Al-Al2O3-MgO particulate MMCs up to 573 K

Al-Al₂O₃-MgO squeeze-cast composites were prepared using a modified “MgO-coating” technique and their tensile behaviour up to 300°C (573 K) evaluated. In each case, 10 wt% total powder mixture (Al₂O₃ + MgO) containing 15% MgO was stirred into well-superheated Al melt and the stirred slurry was squeezed in the pressure range 80–140 MPa using a 60t semi-automatic hydraulic press and alloy-cast iron dies. The tensile behaviour at 100, 200 and 300 °C (373, 473 and 573 K) of the squeezed composites (70 mm diameter, 60 mm long) was then examined. It was found that the composite squeezed at 140 MPa and ambient die temperature displayed the best tensile properties up to 573 K, the ultimate tensile strength (UTS) values being 207.9, 197.8, 179 and 160.4 MN m⁻² at ambient, 373, 473 and 573 K, respectively. Compared to ordinary gravity chill-cast composite, the UTS of the above composite was higher by 52% at 373 K. This value rose to 161% and 162% at 473 and 573 K, respectively. The above composite retained about 77% of its ambient UTS value at 573 K, while the ordinary gravity chill-cast composite retained only 44% of its ambient UTS value. The performance of the squeezed composite with regard to 0.2% offset yield strength (YS) was distinctly superior to the gravity chill-cast composite. The YS values for the squeezed composite were 119.5, 117.3, 115 and 112.8 MN m⁻² at ambient, 373 K, 473 K and 573 K, respectively. The squeezed composite retained 94.4% of its ambient YS value at 573 K, while the gravity chillcast composite retained only 47.6% of its ambient YS value at the same test temperature. The YS of squeezed composite was higher by 105% compared with the YS value of gravity chillcast composite at 573 K. The performance of the squeezed composite progressively improved compared to gravity chill-cast composite as the test temperature was systematically raised to 573 K. Squeezed composites also exhibited fully ductile fracture features compared to semiductile to brittle fracture features of the gravity chill-cast composites; they also perform better because of the virtual absence of porosity and some degree of grain refinement obtained upon squeezing. Increasing the squeeze pressure in the range 160–240 MPa is likely to improve the properties of the composite further.     

含钪Al-Cu-Li-Zr合金的组织与性能

为了研究微量Sc对Al-3.5Cu-1.5Li-0.12Zr合金组织与性能的影响,采用铸锭冶金法,制备了4种不同Sc含量的Al-3.5Cu-1.5Li-0.12Zr合金.采用室温拉伸力学性能实验、金相显微镜和透射电镜研究了微量Sc对Al-3.5Cu-1.5Li-0.12Zr合金微观组织和拉伸性能的影响.结果表明:添加0.1%Sc能消除铸态合金的枝晶组织,有效地抑制了再结晶的发生,具有一定的强化作用和明显的增塑效应;添加O.15%Sc和0.25%Sc能显著细化合金铸态的晶粒组织,但添加0.15%Sc不能抑制合金固溶过程中再结晶;添加0.25%Sc会促进合金固溶过程中的再结晶,从而降低合金的强度.合金中较适宜的Sc加入量为0.10%～0.15%,此时合金既具有较高的强度,又兼具较好的塑性.     

Microstructures and tensile properties of Al-Zn-Cu-Mg-Zr alloys modified with scandium

We melted five types of Al-Zn-Cu-Mg-Zr alloys and added 0.0, 0.1, 0.2, 0.3, and 0.5 (wt.%) of scandium. Its influence on the microstructure of alloys and their mechanical properties is studied with the help of optical transmission and scanning electron microscopes. An insignificant amount of scandium promoted the formation of Al₃ (Sc, Zr) particles. These particles efficiently clean the microstructure, decelerate and preserve recrystallization, and fix dislocations and substructures. The strength of the alloys increases for high levels of plasticity. It is shown that the optimal properties of the alloys with 0.21% Sc are attained after holding in a solution for 40 min at 475°C and aging for 24 h at 120°C. The strength of the alloys increases mainly as a result of dispersion solidification and microstructural hardening with Al₃ (Sc, Zr) particles. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 1, pp. 100–103, January–February, 2008.     

Microstructure and properties of AlTiNiMnBx high entropy alloys

Abstract

AlTiNiMnB _x (x=0˙1, 0˙2, 0˙4 and 0˙5) high entropy alloys are prepared by an arc furnace. The results show that the alloys have a single bcc crystal structure. Boron additions lead to distortion of the crystal lattice and alloy strengthening. The highest hardness (779 HV) is achieved with 0˙5 at.-%B.     

Microstructure and soft-magnetic properties of FeCoPCCu nanocrystalline alloys

Fe_83.2-xCo_xP₁₀C₆Cu_0.8 (x = 0, 4, 6, 8 and 10) alloys with a high amorphous-forming ability and good soft-magnetic properties were successfully synthesized. Saturation magnetic flux density (B_s) is effectively enhanced from 1.53 T to 1.61 T for as-quenched alloy by minor Co addition, which is consistent well with the result of the linear relationship between average magnetic moment and magnetic valence. For Co-contained alloys, the value of corecivity (H_c) is mainly determined by magneto-crystalline anisotropy, while effective permeability (μ_e) is dominated by grain size and average saturation polarization. After proper heat treatment, the Fe_79.2Co₄P₁₀C₆Cu_0.8 nanocrystalline alloy exhibited excellent soft-magnetic properties including a high B_s of 1.8 T, a low H_c of 6.6 A/m and a high μ_e of 15,510, which is closely related to the high volume fraction of α-(Fe, Co) grains and refined uniform nanocrystalline microstructure.     

Microstructure and mechanical properties of FexCoCrNiMn high-entropy alloys

The microstructure and tensile properties of Fe_xCoCrNiMn high-entropy alloys (HEAs) were investigated. It was found that the Fe_xCoCrNiMn HEA has a single face-centered cubic (fcc) structure in a wide range of Fe content. Further increasing the Fe content endowed the Fe_xCoCrNiMn alloys with an fcc/body-centered cubic (bcc) dual-phase structure. The yield strength of the Fe_xCoCrNiMn HEAs slightly decreased with the increase of Fe content. An excellent combination of strength and ductility was achieved in the Fe_xCoCrNiMn HEA with higher Fe content, which can be attributed to the outstanding deformation coordination capability of the fcc/bcc dual phase structure.     

Microstructure and tensile properties of aged Superalpha 2 intermetallic compound

Abstract

Specimens of commercially available Superalpha 2 were solution heat treated at 1060°C in the (α₂ + β phase field, air cooled, then aged at temperatures between 650 and 950°C followed by air cooling. During aging, the B2 phase was more stable than expected from earlier work. The aged specimens were tensile tested to failure at room temperature and microstructural studies were carried out using optical microscopy, scanning electron microscopy, and analytical transmission electron microscopy. It was found that the strength of Superalpha 2 could be dramatically increased by aging at low temperatures, which refines the β matrix. The ductility at room temperature was observed to depend on the volume fraction of retained B2 phase.

MST/1578     

Microstructure evolution and mechanical behavior of Ni-rich Ni-Mn-Ga alloys under compressive and tensile stresses

The microstructure evolution and mechanical behavior in directionally solidified Ni-rich Ni-Mn-Ga alloys with nominal compositions of Ni58Mn25Ga17 and Ni60Mn25G...     

Microstructure characterization and tensile properties of direct squeeze cast and gravity die cast 2017A wrought Al alloy

Squeeze casting is a pressurized solidification process wherein finished components can be produced in a single process from molten metal to solid utilizing re-useable die tools. This one activates different physical processes which have metallurgical repercussions on the cast material structure. Desirable features of both casting and forging are combined in this hybrid method. 2017A aluminium alloy, conventionally used for wrought products, has been successfully cast using direct squeeze casting. Squeeze casting with an applied pressure removes the defects observed in gravity die cast samples. Tensile properties and microstructures are investigated. The results show that the finer microstructure was achieved through the squeeze casting. Furthermore, higher pressures improved the fracture properties and decreased the percentage of porosity of the cast alloy. The ultimate tensile strength, the yield strength and the elongation of the squeezed cast samples improved when the squeeze pressure increased.     

Influence of grain size on tensile properties of Al-Mg alloys

Abstract

Grain size refinement is an important strengthening mechanism in Al-Mg 5000 series alloys, which have a relatively large Hall-Petch slope compared with other Al alloys. In addition, the high work hardening rate exhibited by Al-Mg alloys provides excellent formability. This paper investigates the influence of grain size on the flow stress over a range of strains, and in several different Al-Mg alloys. It is found that the Hall-Petch slope decreases after yield, indicating that the large grain size effect is primarily associated with initiating plasticity in these alloys. Beyond yield the slope decreases to a value equivalent to other, non-Mg containing alloys, and shows no clear dependence on strain. The intercept stress from the Hall-Petch plots at different strains is non-linear with ? 1/2 for alloys containing up to 3 wt-%Mg, which indicates that the free slip distance is strain dependent in these alloys. In an Al-5 wt-%Mg alloy the intercept stress is linear with ? 1/2, indicating that solute atoms are controlling the free slip distance. If Mn is added to the Al-5 wt-%Mg alloy, as it is in commercial alloys, it has little influence on the grain size dependence, but it does increase the frictional stress at the highest Mn level of 0.7 wt-%.