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As a part of my major project I have taken plates of Al6061 samples and butt welded them with friction stir welding machine. During welding I have incorporated metal oxide Nano particles into weld zone of each couple ( ZnO into one couple and SiO2 into other couple) . I thought these nano particles could improve the weld zone strength by going into the interstitial sites. But in the tension test there was no appreciable difference between yield strength of paret weld sample( without metal oxide nano particles) and that of nano particles incorporated sample. And even their corrosion properties were also similar. Can anyone please explain me why did the metal oxide nano particles had not shown any change in mechanical and corrosion properties.

Two plates Al6061 each with 30cm length, 6cm width and 0.6cm thickness were taken. I have made small grooves(9 grooves on each plate maintaining 5 cm between each hole) on the lateral faces of two plates along length side and incorporated 5mg of metal oxide nano particles into each hole ( 9 holes on each plate.therefore 18 holes on two plates and hence 90mg into each couple). Then I carefully joined the two plates with friction stir welding. I'm not able to insert a figure which could make the explanation easier.

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    $\begingroup$ This looks like an interesting but difficult question. Could you provide more details about the experimental technique? Fit example how did you introduce the oxides and how much oxide was added? $\endgroup$
    – DanielSank
    Commented Aug 16, 2016 at 17:05
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    $\begingroup$ Are you sure that your nanoparticles ended up within the weld? They could beak up, evaporate, diffuse to the surface, ... Just to state, it's not trivial to make sure that your nanoparticles are at the correct location. Even more problematic, they may close by, where you need them, but may not be exactly at voids or interstitials, where they would help you. Do you have any characterization methods to analyze your welds? $\endgroup$
    – engineer
    Commented Aug 17, 2016 at 8:41
  • $\begingroup$ You can try uploading your pictures to any file hosting, like imgur, and give a link here. $\endgroup$
    – svavil
    Commented Aug 17, 2016 at 11:24
  • $\begingroup$ Yes..we did fractograhy using FESEM and found out that the nano particles are sitting right at the dimples..this had aroused a doubt in our minds that these nano particles could be the crack initiation points however we aren't clear of that. But to our surprise we didn't find any diffraction peaks in XRD pattern when we characterised the weld region with XRD. We thought this was because of the fact that x-rays only analyse few micron depth of sample and inserted nano particles could be more deeper. $\endgroup$
    – Lavakumar
    Commented Aug 19, 2016 at 2:57

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