The homogenization treatment is essential for TiB2/6082Al composite to eliminate elements segregation and coarse nonequilibrium phases, however, the microstructure evolution and modification mechanisms of TiB2 during homogenization process remain insufficiently understood. In present work, the homogenization process of TiB2/6082Al composite was optimized systematically, and the microstructure evolution during the casting and homogenization was thoroughly clarified. The microstructure of as-cast TiB2/6082Al is composed of fine equiaxed grains with average size of 64.5 mu m and coarse nonequilibrium phase. With the homogenization temperature increases from 540 to 560 degrees C, the fraction of continuous Al(Fe,Mn)Si phase decreases significantly, while overburning occurs with the temperature further increases to 570 and 580 degrees C. During the homogenization under optimal process (560 degrees C/10 h), the coarse Al(Fe,Mn)Si and Al3Ti dissolved into matrix through the diffusion process driven by concentration gradient, and promotes the homogenization of component and microstructure.
In this paper, CoCrFeNiCuPrx (x = 0, 0.05, 0.1, 0.15, 0.2) high entropy alloy was prepared by mechanical alloying (MA)+ fast hot-pressing sintering (FHP), and the influence of Pr content on the microstructure and mechanical properties of the high entropy alloy was investigated. The results show that the CoCrFeNiCuPrx high entropy alloy powder is all composed of FCC structure. After adding Pr, the phase structure of the alloy bulk changes from Cr-poor FCC phase and Cr-rich BCC phase to Cr-poor and Ni-rich FCC phase, Cr-rich BCC phase, and hexagonal structure precipitation phase rich in Pr and Ni. With the increase of Pr content, the precipitated phase gradually aggregates and grows from dispersed fine particles into irregularly shaped masses. The compressive yield strength of the alloy first increases and then decreases with the increase of Pr content. The plastic strain gradually increases and the hardness gradually decreases. Both its yield strength and hardness are greater than those of the high-entropy alloy without Pr. The CoCrFeNiCuPr0.1 high entropy alloy exhibits outstanding comprehensive mechanical properties, with its compressive yield strength, compressive strength, plastic strain, and Vickers hardness reaching 1556.71, 1805.71, 21.16%, and 992.14 HV, respectively.
To investigate the effect of solution treatment temperature on the precipitation behavior of the second phase and the mechanical properties of the T6-treated Al–1.2Mg–2.4Si–0.6Mn alloy, this study employed XRD, SEM, and EBSD techniques to analyze the microstructure, combined with mechanical property testing, to investigate the evolution of microstructure and changes in mechanical properties of the alloy at solution treatment temperatures of 450, 490, 530, and 570°C. The results indicate that the solution treatment temperature significantly regulates the dissolution and precipitation of the second phase of the alloy. As the solution treatment temperature increased, the atoms were fully incorporated into the matrix, and the amounts of Mg2Si and Al19Mn4 phases precipitated during aging increased. At 530°C, the precipitated phases Mg2Si and Al19Mn4 were dispersed without significant coarsening or agglomeration, the dislocation density was low, and lattice distortion was minimal, indicating that the dissolution and precipitation of the second phase were complete. The strengthening effect of dislocation pinning by the second phase was optimized, and the alloy achieved optimal mechanical properties: hardness of 135.6 HV, yield strength of 271.1 MPa, and tensile strength of 301.2 MPa. At 570°C, the alloy undergoes overheating, resulting in the coarsening and agglomeration of the second phase, as well as the melting of low-melting-point phases at grain boundaries, leading to a significant decline in properties, with plasticity dropping to only 1.09
The electrical resistance and Hall effect have been studied for platinum films 3–57 nm thick, prepared by magnetron sputtering on nonmagnetic glass substrates, in the temperature range of 83–293 K. The thickness dependence of the resistivity and temperature coefficient of resistance of platinum films is shown to be satisfactorily described by the Fuchs model, despite the multiband nature of conductivity in platinum. The effective mean free path is estimated. It is established that, with temperature changes, the primary scattering mechanism in these films is the interaction of charge carriers with lattice vibrations, while the contribution of scattering by magnetic impurities is insignificant. The shape of the field dependences of the Hall resistance is shown to be determined by the ratio of the platinum film thickness to the effective mean free path.
Ferromagnetic properties of the disordered fcc Fe_xNi_1 - x alloy at 0.1 ⩽ x ⩽ 0.6 , namely,—mean and local magnetic moments, spin fluctuations and spin-wave stiffness, are studied as functions of nickel concentration at low temperatures. Mean magnetic moment calculated in the low-temperature approximation of the dynamic spin-fluctuation theory obeys the T^3/2 law. Mean magnetic moment has larger deviation from the Slater—Pauling curve at smaller nickel concentrations, while local magnetic moment deviation from the Slater—Pauling curve is small for all concentrations. Temperature dependence of the spin-wave stiffness is found to be in good agreement with a phenomenological expression fitted to (based on the results of) experiment.
