Study on solution expansion of the Cu-W immiscible alloy system by pulsed electron beam

Abstract

BackgroundCu-W composites are widely used in electric power, electronics, and plastic forming owing to the excellent electrical and thermal conductivities of copper combined with the outstanding strength and thermal properties of tungsten.PurposeThis study aims to investigate the extension of the solid solubility of the Cu-W immiscible system under high current pulsed electron beam (HCPEB) irradiation.MethodsFirst of all, the Cu-15W powder mixture was sintered by vacuum at 850 ℃ after ball milling for 5 h to prepare the Cu-W composites. After polishing, the Cu-W composites was exposed by a HOPE-1 type HCPEB device with 1, 5, 10 and 15 pulses, respectively. Then, Rigaku D/Max-2500/pc X-ray diffractometer (XRD) was used to analyze the phase constitutes of the milling powder, sintered samples and irradiated samples. The surface morphology was observed by JEOL JSM-7001F field emission scanning electron microscope (SEM). The energy dispersive spectrometer (EDS) in SEM was used for the examination of micro-region composition. Finally, the microstructures in the modified layer were characterized by JEOL-2100F transmission electron microscopy (TEM). The surface hardness of the sintered and irradiated samples with different pulses was measured using the HVS-1000 Vickers hardness tester.ResultsThe results reveal that Cu(W) solid solutions were formed during the process of ball milling, and the mass fraction of the solute element W in the Cu(W) solid solution reaches 0.88% after 5 h of ball milling. It was discovered that the solid solution undergoes exsolution reaction during heating using differential scanning calorimeter (DSC). The sintered sample surface was irradiated by a pulsed electron beam. The results demonstrate the formation of solid solution phase after HCPEB irradiation, whose solubility increases with the increase of the number of pulses. After 10 pulse irradiations, the mass percentage of solute element (W) in Cu(W) solid solutions reaches 1.63%. The surface hardness of irradiated samples increases significantly after HCPEB irradiation, and reaches 237.1 HV after 10-pulsed irradiation. Surface hardening is primarily caused by of solid solution strengthening and dispersion strengthening.ConclusionsThe present paper provides a meaningful instruction for preparing the immiscible alloy with high solid solubility and the excellent performance.

Keywords

• high-current pulsed electron beam (hcpeb)
• cu-w
• ball mill
• microstructure
• solid solubility