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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.

In this paper, the wettability and growth behaviors of interfacial intermetallic compounds (IMCs) in the Sn/Co and Sn/Cu liquid/solid couples were comparatively investigated. In situ tensile tests were conducted to evaluate the mechanical properties of the Co/Sn(IMCs)/Co and Cu/Sn(IMCs)/Cu joints. The wettability of Sn on Cu substrate was better than that of Co substrate. The lath-like CoSn3 IMCs limited the improvement of wettability of Sn on Co substrate, even if the soldering temperature was increased. The Sn/Co couples showed an acceptable wettability for electronic application. During liquid aging, the rapid growing interfacial CoSn3 were controlled by the combination of chemical reaction and atomic diffusion. Grain boundary diffusion should be responsible for the growth of Cu6Sn5 in the Sn/Cu liquid/solid couples. The tensile strength and elongation of the Co/CoSn3/Co joints were basically equal to that of the Cu/IMCs/Cu full IMCs joints. Interfacial IMCs cracks were more likely to occur in the joints fabricated by Co substrate. The Co/CoSn3/Co sandwich structure can be fabricated within a remarkable short period of time at low temperature without pressure. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of Sn-0.7Cu solder alloy and Sn-0.7Cu with 1.0–5.0 wt% indium addition were investigated in this study. With indium added into Sn-0.7Cu solder, the melting temperature decreased and the reaction temperature increased. Coarse grains of Cu 6 (Sn,In) 5 intermetallic compounds (IMCs) were formed in the alloy matrix when the indium content increased to 1.0 wt%. Indium was evenly distributed in the β-Sn phase and Cu 6 (Sn,In) 5 IMCs in as-prepared In-containing solder alloys. After isothermal aging, indium accumulated gradually in the Cu 6 (Sn,In) 5 IMCs while decreasing its content in the β-Sn phase. Tensile test results indicated that the ultimate tensile strength increased obviously and that the elongation decreased significantly with indium addition. Sawtooths were observed in the stress-strain curves of all aged In-containing alloys. A model describing a coherent relationship between the β-Sn phase and the Cu 6 (Sn,In) 5 phase was proposed to explain this phenomenon. The fracture surface of the Sn-0.7Cu alloy exhibited a ductile fracture mode while a mixed ductile-brittle fracture mode occurred when excessive indium was added into Sn-0.7Cu alloys. [ABSTRACT FROM AUTHOR]

The bonding process of Co/Sn/Cu couple has been conducted at 270 °C. The microstructure evolution was observed. The spreading test of Cu/Sn- xCo and Co/Sn- xCu was conducted to explain the microstructure evolution of Co/Sn/Cu couple. The results showed that the main interfacial intermetallic compounds (IMCs) layer of Cu/Sn side of Co/Sn/Cu couple was (Cu, Co)Sn, as the dissolution of Co from Co substrate to solder layer. The (Cu, Co)Sn IMCs layer only thickened slightly during bonding process as large amount of the (Cu, Co)Sn IMCs layer dissociated into solder alloy layer. As the adsorbing effect of Co substrate on the dissociating (Cu, Co)Sn IMCs, there was a thick (Cu, Co)Sn IMCs layer covered on the surface of Co substrate at the early stage of bonding process. For longer bonding time (> 30 min), the (Co, Cu)Sn and (Co, Cu)Sn IMCs generated on the Co/(Cu, Co)Sn interface as the diffusion of Sn atom from liquid solder alloy to Co/(Cu, Co)Sn interface. The Co/Sn/Cu joint bonded for 60 min could work at the temperature of 300 °C. The shear strength of joints bonded for 20 and 30 min was approximate 45 MPa. The shear strength of joints bonded for a time more than 30 min declined gradually as the generation of (Co, Cu)Sn IMCs. [ABSTRACT FROM AUTHOR]

The microstructure evolution of solder matrix and interfacial intermetallic compounds (IMCs) of Cu/Sn37Pb/Sn3.0Ag0.5Cu/Sn37P/Cu structural composite joints were investigated under low-density current stressing of 2.0×10 3 A/cm 2 at 100 °C. Cu flux diffusion induced by electro-migration was delayed by Ag 3 Sn particles in eutectic phase of Sn3.0Ag0.5Cu solder, by which Cu 6 Sn 5 particles could not reach the interfacial IMC at anode side, and then the growth of interfacial IMC or regular polarity effect at node was inhibited. Coarsened Cu 6 Sn 5 particles were accumulated at the fusion zone between SnAgCu and SnPb close to anode side. Micro-cracks were found at cathode side after current stressing for as short as 100 h, and increased with current stressing time until the failure of solder joint. [ABSTRACT FROM AUTHOR]

In order to improve the performance of the inner wall of the 316L hydraulic cylinder, FeCoNiCrMox (x = 0.2, 0.4, 0.6) high entropy alloy coatings were prepared by laser cladding. The effects of the Mo element on the phase, microstructure, hardness, and tribological as well as electrochemical behaviors of the coating were investigated. The results show that the coatings consist of the FCC phase. The FCC phase increases, and the grain orientation becomes more complex with increased Mo element content. The coatings are mainly composed of columnar and equiaxial crystals. Mo0.4 coating has the finest grain structure, resulting in the coating with a maximum hardness of 421.99 HV, 2.11 times that of the substrate. The nanoindentation test shows that the elastic modulus of the HEA coating increases with the increase of Mo content. The dry sliding wear test shows that adding the Mo element improves the wear performance of the coating. The wear volume loss and wear rate of Mo0.4 coating were the lowest, 12.242 mg and 2.88 × 10−4 mm3•N−1•m−1, respectively. In the 3.5 wt% NaCl solution, the polarization curves and EIS results indicated that adding the Mo element improved the corrosion resistance of the coating. The FeCoNiCrMox coatings significantly improved the hardness, tribological, and electrochemical behaviors of the 316L substrate. [Display omitted] • The FeCoNiCrMox coatings on the inwall of 316 L tube were composed of FCC phase. • The addition of Mo element refines the microstructure of the HEA coating. • The addition of Mo element improves the mechanical properties of the HEA coating. • The Mo element improves the tribological and electrochemical behaviors of the HEA coating. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the microstructure and properties of the Al Mo laser-alloyed layer induced by high-current pulsed electron beam (HCPEB) irradiation. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to investigate the microstructures of the modified layer. The microhardness and friction properties were also measured. The microstructural observation shows that HCPEB irradiation led to the formation of a modified layer approximately a dozen microns thick, which was the absence of the pores. It was found that the flower- and strip-like Al Mo particles were dissolved to form nano-size particles consisting of Al 5 Mo (h2), Al 12 Mo, and Al 17 Mo 4 phase after HCPEB irradiation. Additionally, the slip bands and high-density dislocations were formed in the modified layer. The refined microstructure significantly enhanced the microhardness of the laser-alloyed layer. A quantitative evaluation was conducted to investigate the individual contributions of four strengthening mechanisms to the strength of the modified layer, which indicated that dislocation and grain boundary strengthening were dominant. The results of sliding wear tests show that the modified layer exhibited superior properties compared to the laser alloying layer, which was attributed to the formation of crystal defects, solid solutions, and nanoparticles. • The Al-Mo laser-alloyed layer was exposed to HCPEB irradiation. • The refined precipitates and grains were formed due to the dissolution of large-sized particles. • The enhanced friction property and improved hardness are associated with increasing pulses. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the solid solution strengthening (SSS) of Sn, Pb in aluminum (Al) matrix under high current pulses electron beam (HCPEB) irradiation. First-principles calculations method was adopted to quantify the effect of SSS with various concentrations. The capacity to strengthen is correlated with a nearly linear concentration dependency. In experimental section, the microstructures of the Pb/ and Sn/Al systems were characterized by SEM and TEM analysis. The solubility limit of both systems under HCPEB irradiation were calculated by a simple thermodynamic model. It is found that the Sn/Al system has a higher solid solubility, compared to that of the Pb/Al. In addition, the values of SSS of the Pb/ and Sn/Al systems were estimated. The results show that the Sn/Al system has higher strengthening ability than that of the Pb/Al system under HCPEB irradiation due to the different solid solubility, which is consistent with theory. [Display omitted] • Extension of solid solutions in the Pb/ and Sn/Al systems was achieved by HCPEB irradiation. • The solid solubility was calculated by a thermodynamic model. • The SSS of Sn and Pb in Al was assessed using a combination of first principles calculations and experimental results. [ABSTRACT FROM AUTHOR]

In this study, the effect of adding trace Er element on the microstructure and mechanical properties of AA6061 twin-roll casting sheet was evaluated. An NF6–300 vertical twin-roll cast-rolling mill was used to prepare AA6061 twin-roll casting sheet with different Er contents, and the main phase morphology and formation mechanism of Er in the alloy were analyzed using microstructure observation, scanning electron microscopy, transmission electron microscopy, and other microstructure analysis techniques. The results show that the addition of a small amount of Er can form the primary Al 3 Er phase in the alloy. This phase structure becomes an excellent heterogeneous nucleation core of α-Al. This significantly affects the grain size of AA6061 TRC sheets. In addition, Er interacts with the Fe in the TRC sheet. Therefore, the iron-rich phase in the structure changes from coarse needle-like and skeletal shapes to smaller short rods and blocks, and micron-sized spheroids or lumps appear in the structure. Spheroid-like iron-rich phase contains Er. When the amount of Er addition exceeds 0.4 wt%, the number of rare-earth compounds and impurity phases in the structure increases significantly, and they mainly precipitate along the grain boundaries. This increases the strengthening effect of second phase and greatly reduces the plasticity of the material. When the amount of Er addition reaches 0.4 wt%, the comprehensive mechanical properties of TRC sheet are the best. At this time, the tensile strength, yield strength, and elongation are 160.14 MPa, 124.77 MPa, and 10.68%, respectively. • Effect of Er element on the microstructure and mechanical properties of twin-roll casting 6061 Al alloy sheet. • Er can form the primary Al3Er phase, which is an excellent heterogeneous nucleation core. • Er promote the transformation of Fe phase, and form micron-sized spheroids -like iron-rich phase contains Er. [ABSTRACT FROM AUTHOR]

AA6061 twin roll casting plate was annealed and then the hot rolling experiment was carried. Effect of Mn content on microstructure evolution and recrystallization behavior was investigated. The results show that Mn element can significantly change the recrystallization behavior of the alloy and produce particle induced recrystallization (PSN) effect. The mechanical properties of the plate would be effectively improved with appropriate Mn content. With the increase of Mn content in cast rolling plate, the number of recrystallized grains in the alloy increases; The strength and hardness of 6061 cast rolled plate increases first and then decreases with the increase of Mn content in the alloy, and the elongation decreases gradually with the increase of Mn content. Comprehensively considered, when the Mn content is 0.46%, the mechanical properties of the plate are optimal, i.e., tensile strength 197.36 MPa, yield strength 157.89 MPa and elongation 6.23% respectively. [ABSTRACT FROM AUTHOR]

In this investigation, the 6061-T6 double-side friction stir welding (DS-FSW) plates with a thickness of 6 mm were rolled to different thickness. The microstructural evolution during rolling process was systematically studied based on the technologies of XRD, EBSD and TEM. The tensile test showed the evolution of yield strength (YS), ultimate tensile strength (UTS) and elongation during rolling process. The results revealed that the deformation mechanism of stirring zone (SZ) during rolling was grain rotation of fine grain. It contributed to a weaker dislocation density improvement in SZ. For the strengthening effect, all of the grain refine strengthening, precipitating strengthening, and solid solution strengthening of SZ were stronger than those in base metal (BM). However, the poor dislocation strengthening effect of SZ resulted in its lower YS compared with that of BM. The fracture of SZ depended on the debonding of plastic flow layers. The special fracture mode determined the lower UTS and elongation of SZ compared with those of BM. [ABSTRACT FROM AUTHOR]