| 5083-H321aluminum alloy sheet was processed by Friction Stir Process. With the UMT-3multi-functional friction and wear tester, using the ball-block dual reciprocating friction and wear test method at room temperature under dry friction and wear test conditions, the comparative study of friction and wear properties of5083-H321aluminum alloy rolled plate and its FSP processed sheet to explore the influence law of loading time and load parameters on friction coefficient and wear loss of the two. The wear scar morphology and composition of the specimen worn surface, wear debris and dual friction surface under different time and loads were observed and detected with scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) and the friction and wear mechanisms were discussed. By means of the optical microscope (OM), electron backscatter diffraction analyzer (EBSD) and orientation microscopy imaging analysis techniques (OIM) to analyze the influence law of FSP on the organization characteristics of5083-H321aluminum alloy sheet and explore the mechanisms of FSP improving friction and wear properties. The main contents and results are as follows:1. The variation law of friction coefficient for5083-H321aluminum alloy and friction stir processed plate samples with time and load was demonstrated. On the initial state of slide(0-600s), the friction coefficients of both materials are steady. However, the friction coefficient of FSP5083descends earlier than the other one, and its average value is slightly less than the one of5083-H321. The two friction coefficients decrease gradually and tend to be close with increasing the sliding time between600s and1500s. When the load is20,30,35,40N. and on the initial state of slide (0-600s), the average friction coefficient of FSP5083is slightly less than the one of5083-H321. However, the effect of loading force on the friction coefficient is not important. The skin friction coefficient of5083-H321aluminum decreases while processed by FSP.2. The variation law of the wear loss for5083-H321aluminum alloy and friction stir processed plate samples with time and load was demonstrated. With the growth of the sliding time, the total wear loss of the two both increases and both wear loss get reduced gradually in one by one period, and the total wear loss of FSP5083is obviously less than the one of 5083-H321.The difference value between the two firstly increases and then decreases, reaching to the maximum at the600s; The wear loss increases obviously with increasing load; FSP can obviously improves the abrasive resistance for5083-H321aluminum alloy sheet.3. The morphology of the wear surface and wear debris for5083-H321aluminum alloy and friction stir processed plate specimen was demonstrated and the mechanisms in the process of the friction and wear were discussed. The wear surface of the two show the morphology of the mill ditch, flanging, pits, cracks, debris and so on, in which, the debris content of the5083-H321aluminum alloy is more and plastic deformation of friction stir processed specimen is more serious, both wear debris morphology are massive, the debris volume increases with increasing load. By EDS analysis it is found that oxidation occurs on the friction surface, and appears adhesion phenomenon of the specimen on the friction dual. The main wear mechanisms are adhesive wear, abrasive wear and fatigue wear.4. The effect law of FSP on the organizational characteristics for5083-H321aluminum alloy sheet was demonstrated and the forming mechanism was analyzed. The forming property of FSP5083aluminum alloy is good and with no holes, cracks and other defects. Due to the thermal-mechanical difference, the organization of friction stir processed5083-H321aluminum alloy can be divided into4different zones including the nugget zone, thermal-mechanical zone, heat affected zone and shaft shoulder function zone and every zone has different organization characteristics from the base metal, among which the grains in the shaft shoulder function zone show obvious refining.5083-H321aluminum alloy contains brass texture｛11O｝<-112>, S texture｛123｝<63-4> and other texture components, after FSP processing, the texture mainly translate to ｛112｝<1-10> orientation and in the friction surface parallel with the sheet rolling surface, the content of the grains for crystal face (111) parallel to the friction surface get significantly increased.5. The friction and wear property improvement mechanism of FSP on5083-H321aluminum alloy was discussed. The Wear surface morphology characteristics show that plastic deformation occurs in the friction and wear process. The fine grain layer in the shaft shoulder function zone can avoid the adverse effects of premature birth and development of the cracks in the plastic deformation process, as a result, the fatigue wear can be inhibited to some extent and the hardening effect on the friction surface can be enhanced in the course of friction. The effect of anti-adhesive and abrasive friction and wear get enhanced. Due to the crystal face (111) as a close-packed surface has low surface energy, correspondingly, the adhesion coefficient between friction dual and the sample get reduced, thereby increasing the friction and wear properties. These two factors are the main mechanisms for FSP to improve the frictional wearing property of5083-H321aluminum plate. |
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