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The aluminum alloy performance gradient plate was prepared by friction stir joining. Analysis results of the macro morphology, microstructure, and hardness of the aluminum alloy performance gradient plate prepared under various parameters show that when the feed speed of the stirring tool is 250 mm/min, the downward pressure of the stirring tool is 6.6 mm, and the rotation speed of the stirring tool changes from 200 rpm to 800 rpm. The macroscopic morphology of the aluminum alloy gradient plates prepared by the method first changed from burr to smooth, and vice versa. There is a different cross-section morphology of the prepared aluminum alloy gradient plates, however, the aluminum alloy plates are stirred and involved with each other, and the grains of the prepared plates are refined. The hardness of the upper and lower surfaces of the aluminum alloy gradient sheet decreases, whereas that of the upper surface of the side increases, and that of the middle and bottom sides also decreases. However, the hardness of the middle side of the sheet prepared with the rotation speed of the stirring tool at 800 rpm increases, but that of the bottom side still decreases. Obtained through analysis that the performance of the aluminum alloy gradient sheet prepared at the stirring tool rotation speed of 500 rpm increases in equal proportion to achieve a good performance gradient change. [ABSTRACT FROM AUTHOR]

The state of the simulation technology widely used in friction stir welding (FSW) studies requires greater and greater accuracy. An analysis is made of an FSW dynamic heat source model and related information. The model is combined with results from FSW experiments and the welding temperature field. A relationship is obtained for the friction coefficient between the tool and welding materials with temperature. By incorporating tool force measurements and analysis, a simulation model which is much more in line with actual FSW results is thus established. In the simulation process, the temperature of each part of the tool, the material model, fixture constraints, and the role of tool–material forces are analyzed and discussed in detail. In the new model, the different input heats on the advancing and retreating sides on the shoulder, the pin surround, and top of the pin are distinguished. The mechanical properties of the materials with change in temperature and the constitutive equations for the welding, before and after, are obtained. The contact relationship between the fixture and workpiece was built. In the welding process, the forces of the tool toward the welding material were applied. The 7022 aluminum alloy FSW process was simulated by the constructed simulation model. The temperature field, residual stress, and deformation in the simulations were in good agreement with the experiment results. [ABSTRACT FROM AUTHOR]

Graphene oxide particles (GOp) were implanted on the surface of H62 copper alloy by friction stir surface processing (FSSP) to obtain a H62/GOp modified layer. The recrystallization microstructure, friction, and wear property, and hardness of the modified layer were studied and analyzed. The results show that the GOp has a good dispersion in the copper matrix without obvious aggregation. The recrystallization on the layer of the modified copper alloy resulted in obvious grain refinement. When the rotating speed of the tool was 900 rpm, and the feed speed of the tool was 200 mm/min, the highest hardness value and wear resistance of the modified layer samples were obtained. The hardness value was 25.2% higher than that of the base metal. The average friction coefficient was 39.5% lower than that of the base metal. When the tool rotating speed was 1300 rpm, and the tool feed speed was 160 mm/min, the hardness value and wear resistance of the modified layer were relatively low. The hardness value was approximately 4% higher than that of the base metal. The average friction coefficient was 15.8% less than that of the base metal. The hardness and wear resistance of the modified layer were better than those of the base material under various parameters of FSSP. [ABSTRACT FROM AUTHOR]

This study aimed to carry out the friction stir processing (FSP) modification of 7075 aluminum alloy mainly by slotting the base metal and adding the reinforcing phase, and to explore the electrochemical corrosion performance of the modified area. The results showed that the added phases with different mass fractions of TiB2, TiC, and Cf were beneficial to improve the electrochemical corrosion performance of the modified area. Among them, the TiB2 and TiC at different mass fractions had a relatively small improvement in the electrochemical corrosion performance of the FSP-modified area of the base metal, and both had a negative effect when the mass fraction was 5%. The Cf addition phase with a mass fraction of 2% had the most obvious improvement effect. Its corrosion potential E0 was −0.771 V, and the corrosion current density I0 was 4.80875E-6 A · cm2. The analysis showed that the electrochemical performance of Cf and the bonding performance with the base metal were better, and the corrosion process of the base metal could be suppressed during the corrosion process. [ABSTRACT FROM AUTHOR]

The hot rolled 7075 aluminum alloy was modified by friction stir processing (FSP) technology, and the effects of different processing parameters on impact toughness and microstructure of machining region were analyzed. The results showed that the impact toughness of machining region was 2.3 times that of the base metal when the rotation velocity was 1200 r/min and the feed rate was 60 mm/min, which much higher than base metal. The fracture morphology was observed by using scanning electron microscope and found that the morphology of fracture dimple was uniform and smooth. The grains in the weld nugget zone were obviously refined after friction stir processing, and the grain refinement effects were not the same in different processing parameters. [ABSTRACT FROM AUTHOR]

As a key component of friction stir joining (FSJ), tools play an important role in welding quality and welding performance. In this study, the acoustic emission (AE) signal acquisition system was established. The AE signals from FSJ of SiCp/Al composites were analyzed in the time domain, frequency domain, and time-frequency domain respectively. The root mean square (RMS) value, spectrum distribution, and energy distribution of AE signals during FSJ were obtained. The relationship between the tool wear state and the AE signal was studied. The results show that with the increase of welding times, the wear degree of the pin is aggravating. The more serious the tool was worn, the greater the RMS value of the acoustic emission signal was. With the increase of wear, the energy of AE signals gradually moves to the low-frequency region, and the spectrum tends to be concentrated. According to wavelet packet decomposition of AE signals, it has been found that in the frequency bands 3-8, the energy percentage increases with the aggravation of agitation tool wear, while the opposite trend appears in the frequency bands 10-16. [ABSTRACT FROM AUTHOR]