Effect of rolling deformation on microstructure and properties of Cu–Ni–Mo alloy prepared by aluminothermic reaction

The metallic element Mo has almost no solid solubility in copper and can be used as a nucleation particle to refine the grain size and increase the recrystallization temperature of the alloy during solidification. It is expected to obtain copper alloys with good comprehensive properties by reasonably controlling the addition amount of Mo. However, it is difficult to prepare Cu–Mo alloys with uniform structure and there are few related literatures. In this paper, the aluminothermic reaction method, which has the advantages of simple process, low cost, and large size of the prepared alloy, was adopted, and a cluster model with the atomic ratio of Mo and Ni of 1:12 was introduced to design the alloy composition. Here, five alloys with different copper contents were prepared and followed by room temperature rolling with 40%, 60%, and 80% deformation. The results show that the as-cast Cu–Ni–Mo alloys exhibit good formability, have no macroscopic defects and present a small amount of precipitates. With the increase of alloy elements Ni and Mo, the hardness and strength of the alloys increase obviously, while the electrical conductivity decreases gradually. For the rolled alloys, a large number of lamellar deformed structures are formed, the grains are obviously refined, the precipitated phases are broken and the distribution is more uniform, thus the strength and hardness of the alloy increase significantly, the plasticity decrease significantly, while the conductivity changed little. In this study, high-strength samples were obtained, which may be a valuable exploration for the preparation of Cu–Ni–Mo alloy sheets with excellent microstructure and mechanical properties.

Improved Recrystallization Resistance and Welding Properties of Cold-Rolled Al-Mg Alloy Sheets by Microalloying with Sc and Zr

The effects of Sc and Zr element on the recrystallization behavior and microstructure evolution of Al-Mg alloy had been researched in this paper, and meanwhile, the microstructure and mechanical properties of the friction stir welding joints were also analyzed. The results show that the recrystallization and grain growth behavior of Al-Mg-Sc-Zr alloy can be inhibited effectively by microalloying with Sc and Zr. Compared with Al-Mg and Al-Mg-Zr alloys, the recrystallization start temperature and finish temperature of Al-Mg-Sc-Zr alloy increase significantly, and the strength of alloy sheet which subjected to stabilizing annealing is increased by more than 50MPa. Moreover, the recrystallization softening effect of the welded joints microstructure, which caused by the welding temperature field and welding heat input, can be weaken by microalloying with Sc and Zr, the width of recrystallization zone is reduced, the microstructure and properties of the welded joints are improved. The friction stir welding coefficients of Al-Mg-Sc-Zr alloy increases to 86.9%.

Effect of Annealing Temperature on the Microstructure of 2195 Al-Li Alloy Sheet

The annealing temperature is a key parameter for the mechanical properties and microstructure control of the 2195 Al-Li alloy sheet in the annealing process. In the present study, the effect of annealing temperature on the microstructure of 2195 Al-Li alloy sheet was investigated using a general mechanical testing machine, scanning electron microscope (SEM), transmission electron microscope (TEM), and backscattered electron microscope (EBSD). It was found that the optimized annealing temperature for 2195Al-Li alloy sheet of H112 state is 400°C, the alloy sheet shows the satisfactory mechanical properties. In addition, with the increase of annealing temperature, the δ' phase, the θ' phase and the T1 phase are formed in the alloy sheet, which leads to the strength of the alloy increase. Furthermore, the annealing temperature obviously affect the texture component and intensity during annealing treatment process.

Crystallization Process, Structure and Hydrogen Absorption and Desorption Properties of MgxNi10 (x = 20.5-26.5) Alloys with Hypereutectic Composition

We have analyzed crystallization process of the MgxNi10 (x = 20.5 – 26.5) alloys using phase diagram of Mg-Ni system. Their structure, atomic arrangement and crystal defects were tested by XRD, SEM and HRTEM, respectively. Hydrogenation and dehydrogenation behaviors were measured by pressure-composition-isotherm measurement. The results show that the crystallization processes of the MgxNi10 (x = 20.5 and 22.5) alloys are unlike those of the MgxNi10 (x = 24.5 and 26.5) alloys, but their room temperature microstructure all contain Mg2Ni and eutectic structure of Mg2Ni + α-Mg. The alloys are composed of Mg2Ni phase and α-Mg phase. The addition of Mg is beneficial to the formation of eutectic structure. The alloys have all good activation property. At a lower temperature, such as 200 and 250 °C, the hydrogen absorption rate and hydrogen saturation ratio are significantly lower than those of the alloy at the higher temperatures, such as 300 and 350 °C. At 350 °C, the hydrogen absorption capacity of the alloy increase and the hydrogen release efficiency of the alloy decreases with the increase of Mg content. The time of 90% of the amount of saturated hydrogen absorption and desorption of the alloys is not more than 10 and 2 minutes, respectively. The hydrogen desorption rate of the Mg22.5Ni10 alloy in the four investigated alloys is relatively large and up to 7.170 wt.%.min-1.

Effect of Intermediate Thermomechanical Treatment on Microstructure and Mechanical Properties of 2A97 Al-Li Alloy

Effect of intermediate thermomechanical treatment on tensile properties at short-transverse direction, fracture mechanism and microstructure of 2A97 Al-Li alloy thick plate were studied by tensile testing, SEM, EBSD and TEM.The results show that with the increasing of compression deformation, the strength and elongation of the alloy increase first and then decrease slightly. The fracture mode of the alloy changes from quasi-cleavage fracture to high energy ductile fracture. When the compression deformation rises to 20%, the elongated structure are replaced by a more uniform and equiaxial structure. The distribution of δ phase distribute more homogeneously in the grains.

Microstructure and Mechanical Properties of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy Fabricated by Arc Additive Manufacturing with Post Heat Treatment

Wire arc additive manufacturing (WAAM) can achieve low-cost, short-cyclemanufacturing of titanium alloys and has promising application prospects. In this paper, themicrostructure and mechanical properties of both as-deposited and heat-treated Ti-6.5Al-3.5Mo-1.5Zr-0.3Si(TC11) alloys fabricated byWAAM were investigated. The results show that continuousgrain boundary α(αGB) phase and basket-weave microstructure can be observed in the as-depositedTC11 alloy. And the as-deposited alloy exhibits high ductility but low strength. After the annealingtreatment, the microstructure becomes thicker and the strength becomes lower. Accordingly, a duplexheat treatment near β transus was designed. We can observed that the content of α phase in themicrostructure was gradually decreased, and the continuous αGB was broken gradually. As thetemperature increases, the strength and ductility of TC11 alloy increase first and then decrease, andthe best comprehensive mechanical properties are achieved at 970°C.

EFFECT OF AGING TREATMENT PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF Cu-Ni-Si ALLOY

In this paper, effect of cold pre-deformation and sequent aging time and temperature on microstructure and properties of Cu-2.8Ni-1.0Si alloy are reported. The results shown that, hardness and electrical conductivity of alloy increase with increasing cold deformation degree after quenching and subsequent aging. With undeformed specimens after quenching, hardness and electrical conductivity of alloy reach maximum values with subsequent aging at 425 and 475 oC, respectively. Alloy attains maximum hardness of 255 HV5 with aging at 425 oC for 4.5 hours, while maximum electrical conductivity of 38.5 %IACS with aging at 475 oC for 8 hours. In the case of deformed specimens after quenching and subsequent aging, this rule is still preserved. Especially, at 70 % cold pre-deformation degree, alloy attains the maximum hardness of 274.3 HV5 with aging at 425 oC for 3.5 h, while maximum electrical conductivity reaches 42.4 % IACS with aging at 475 oC for 6 h.

Effects of Y on the Microstructure and Mechanical Properties of Mg-Zn-Y-Zr Magnesium Alloys

Mg-Zn-Zr-Y billets with different mass fraction of Y (wt%(Y)=0.2%、0.5%、1.0%、1.5%、2.0%) was prepared by permanent mold casting. The increase in Y content has shown grain refinement effects on the microstructure morphologies of Mg–Zn–Y–Zr alloys. When the content of Y achieves 1.0 wt%, the grain refinement effect of the Y is most obvious than any more contents of the Y content. In the test result of XRD, the type of precipitated phase in Mg-Zn-Zr-Y alloys is related to atomic ratio of Y/Zn. With content of Y increases, atomic ratio of Y/Zn increases,the precipitated phase in alloy is changed from Phase I to Phase W. Tensile strength and extension rate of alloy increase with the increasing of Y content; When Y content reaches 1.0%, mechanical property reaches maximum value.When content of Y exceeds 1.0%, with the increasing of Y content, mechanical property of alloy declines gradually.

Microstructure Evolution and Macro Segregation of Directionally Solidified Hypoeutectic and Hypereutectic Lead-Tin Alloys

Unidirectional solidification is preferred to multidirectional solidification for growing crystals in a particular direction. An experimental set-up consisting of Bridgman type of upward directional solidification was employed for the present investigation. The main aim of the present investigation was to assess the effect of unidirectional upward solidification on the segregation of off-eutectic Pb-Sn alloys at different translational speeds of the experimental set-up. Solidification experiments were conducted on hypoeutectic and hypereutectic Lead-Tin alloys. Different combinations of growth rate V and composition Co. were used to investigate their effect on longitudinal macro segregation. Macro segregation along the length of the samples was observed in hypoeutectic Pb-Sn alloys whereas no such macro segregation was observed in hypereutectic alloys. The intensity of longitudinal macro segregation was found to increase with the increase in initial tin content of the alloy, increase in distance from the chill end and decrease in the solidification rate.

Thermodynamic, structural, surface and transport properties of Zn-Cd liquid alloy at 800 K

The mixing thermodynamic and structural properties of Zn-Cd liquid at 800K has been studied using Flory’s model. To explain the mixing properties of binary liquid alloys, size factor (ф) and ordering energy (ω) are taken into account. Thermodynamic properties like free energy of mixing (GM), activity (a), Heat of mixing (HM) and entropy of mixing (SM) and the microscopic properties like concentration fluctuation in the long wave length limit (Scc(0)) and chemical short range order parameter (α1) have been calculated. Surface property has also been studied with the help of Buttler’s model. The viscosity of the melt has been computed from Kaptay equation and BBK models. Both the viscosity and surface tension of the alloy increase with addition of zinc- component. BIBECHANA 14 (2017) 54-65