Kinetics of discontinuous precipitation in Cu–20Ni–20Mn alloy

The morphology and growth kinetics of discontinuous precipitation （DP） in a Cu-20Ni-20Mn alloy were investigated in the tem- perature range of523-573 K by optical microscopy, scanning electron microscopy, and transmission electron microscopy. A lamellar mixed structure consisting of alternating larnellae of a matrix and NiMn phase was observed in DP colonies. The volume fraction of regions formed by a DP reaction was determined by quantitative metallographic measurements. The kinetics of DP was evaluated on the basis of the John- son-MehI-Avrami Kohnogorov equation, which resulted in a time exponent of approximately 1.5. We confirmed that the nucleation of the discontinuous precipitate was confined to grain edges or boundaries at an early stage of the reaction. The activation energy of DP process was determined to be approximately （72.7 ± 7.2） kJ/mol based on the Arrhenius equation; this result suggests that DP is controlled by gn-ain boundary diffusion. The hardness values exhibited good correlation with the volume fraction of DP; this correlation was attributed to the plvsence of the ordered N iMn phase.

Microstructure and physical properties of Cu-2.3Ni-0.5Si alloy with thermo-mechanical treatment

For Cu-Ni-Si alloys,cold rolling is usually performed after solution treatment to enhance physical properties such as strength and electrical conductivity during the aging process.This paper reports the variation in microstructure and physical properties during the aging process of Cu-2.3Ni-0.5Si alloy cold-rolled at room temperature(RT) and cryogenic temperature(CT).When aged at 450℃ for 2 h,RT-rolled samples exhibited a maximum hardness of HV5234 with an electric conductivity of 39.9% IACS.For CTrolled samples,the peak hardness was achieved when the samples were aged at 450% for 1 h.

Microstructural evolution and properties of a Cu-Cr-Ag alloy during continuous manufacturing process

Microstructure evolution and properties of a Cu-Cr-Ag alloy during the continuous manufacturing process were investigated in detail by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)in the study.The Cu-Cr-Ag alloy rod with uniform compositions is fabricated by upward continuous casting technology.Few of the Cr phases are observed in the ascast alloy.During the continuous extrusion process,the severe shear deformation and the dynamic aging occur.The average grain size of as-extruded alloy is much smaller than that of as-cast alloy.Both fcc and bcc Cr precipitates appear in the matrix.The interaction mode between dislocations and precipitates can be identified as Orowan bypass mode according to the TEM observations.The overall difference in the yield strength between as-cast and as-extruded Cu-Cr-Ag alloy is attributed to solid solution strengthening,grain refinement strengthening,precipitation hardening and working hardening.

Microstructure of phases in a Cu–Zr alloy

The morphology and crystallography of phases in the Cu-0.12% Zr alloy were investigated by scanning electron microscope(SEM), transmission electron microscope(TEM), and high-resolution transmission electron microscope(HRTEM). The results show that the as-cast microstructure of Cu–Zr alloy is mainly Cu matrix and eutectic structure which consist of Cu and Cu5Zr phases with a fine lamellar structure. The disk-shaped and plateliked Cu5Zr phases with fcc structure are found in the matrix, in which habit plane is parallel to {111}a plane of the matrix.Between the copper matrix and Cu5Zr phase,there exists an orientation relationship of [112]a|| [011]Cu5Zr;(111)a||(111)Cu5Zr. The space structure model of Cu5Zr phase can be established.

High-temperature deformation behaviors of Ti-2Al-9.2Mo-2Fe alloy with boron

Hot deformation behaviors of Ti-2Al-9.2Mo-2Fe alloy with boron were investigated in a hot compression test at temperatures ranging from 850 to 1000℃and strain rates ranging from 0.01 to 10.00 s^(-1).With strain rate decreasing and deformation temperature increasing,dynamic recrystallization(DRX)was promoted in both alloys.The nucleation mechanism of DRX involved grain boundary bulging and subgrain rotation.In case of deformation at low temperatures and high strain rates,the boronfree alloy only showed dynamic recovery(DRV)phenomenon.However,due to the particle-stimulated nucleation mechanism of recrystallization by TiB particles,the boron-containing alloy shows DRX at that condition.These DRX grain nuclei are formed by lattice rotation and subgrain growth from deformation zone in the initial grains,which are close to those of TiB particle.Moreover,the flow stress of the boron-containing alloy is lower than that of the boron-free alloy due to the grain refinement during hot deformation process.

Unveiling thermal properties and pump-out blocking in diamond/GaInSn composites as thermal interface materials

Gallium-based liquid metal,as a high-performance thermal interface material,can improve the performance and service life of electronic equipment.This study focuses on the use of diamond as a thermal conductivity enhancement phase to improve the thermal conductivity of GaInSn liquid metal and avoid the overflow of liquid metal during application.In this study,diamond/GaInSn composites were prepared by an ultrasonic-assisted wetting method.The thermal conductivity and contact thermal resistance of diamond/GaInSn composites were characterized by the transient method.The morphology and thermal conductivity of diamond/GalnSn composites were investigated when diamond particles of different diameters were added to GaInSn liquid metal.The addition of large-sized diamond particles can effectively improve the thermal conductivity of thermal interface materials (TIMs) but willcause liquid metal to pump out.

Improving interface adhesion in TiNi wire/shape memory epoxy composites using carbon nanotubes

In order to increase both the interfacial strength and interphase region strength between TiNi wires and shape memory epoxy,a novel interface structure including aminated CNTs was designed.The morphology shows that after electroplating and etching,continuous and homogeneous concave-convex layers form on the surface of astreated TiNi wires,meanwhile aminated CNTs were planted on the surface which could react with shape memory epoxy at the interface region.The interfacial shear strength increases first with the CNT content rising but then a dramatic drop happens,and the maximum is obtained at CNT content of 0.6 g·L^(-1),which is about twice the result of acid etching TiNi wires.

Antibacterial property,corrosion and discoloration resistance of pure copper containing Zn or Ni

This study focused on the effects of Zn and Ni addition on the antibacterial properties and corrosion resistance of copper alloys.The antimicrobial properties of copper and copper alloys were evaluated using Escherichia coli ATCC8739 bacterial strain by employing the overlay and plate counting methods.

Interface evolution of Cu-Ni-Si/Al-Mg-Si clad composite wires after annealing

Interface micros tructures of Cu-Ni-Si/Al-MgSi clad composite wires during isothermal annealing from 623 to 773 K were investigated.The composite wires were fabricated by a drawing process.The evolution of intermetallic compounds(IMCs)was analyzed.A continuous IMCs layer forms only after annealing for 1 min,which may be due to more IMCs nucleation points generated by deep drawing process.IMCs consist of Al_(4)Cu_(9),AlCu and Al_(2)Cu identified by energy-dispersive spectroscopy(EDS)and transmission electron microscopy(TEM).The growth activation energies of total IMCs,Al_(2)Cu,AlCu and Al_(4)Cu_(9),are 98.8,69.4,101.3 and 137.1 kJ·mol^(-1),respectively.The higher growth activation energy of Al_(4)Cu_(9)results in the higher growth rate under high temperature.However,the average interdiffusion coefficient for each IMC calculated by Wagner method shows that interdiffusion in Al_(2)Cu and AlCu is more active than that in Al_(4)Cu_(9).The higher growth rate of Al_(4)Cu_(9)may be caused by the long concentration range.