 So we will now see some of the example of EBSD, EBSD as I have discussed and shown you in the lab is extensively used now for different microstructural analysis, so I am going to show you one example which we have carried out to analyze these solidified microstructure in which EBSD was used to show how the gain refinement happens during under cooling experiments. Well as you know that gain refinement of any material can be either intrinsic or extrinsic. In case of extrinsic gain refinement we add certain refinement agents like titanium diboride in case of aluminum alloys but in case of instinctive gain refinement we do not add any elements or any gain refiner, gain refinement happens because of the fragmentation of the dendrites which formed during the solidification of the alloys or metals and this can happen because of many reasons. So one of the reason is the recrystallization and the recovery and recrystallization which takes place during the solidification or just after the solidification event. As you know the solidification leads to volume change of the material from the liquid to solid and this can lead to stress generation and stress can cause at high temperature recrystallization and recrystallization can lead to gain refinement. So let us see one example like that. So the one which we have done in our research is from iron germinium phase diagram. So if you look at iron germinium phase diagram it is basically crowded with so many phases but I am going to consider only the alloy which 18 percent germinium, the one which are marked by rate and as you see here if you start solidifying from the liquid state it will form alpha Fe that is BCC alpha iron with certain amount of germinium and then just below the solidus temperature it will undergo ordering so therefore BCC alpha iron will become B2 and then further cooling leads to DO3 or the second order ordering. So therefore this ordering in a solid state can also lead to stress generation and that can also cause recrystallization to happen. So by knowing that we are going to see how this RBSD technique can be used to analyze the microstructures. I will show you some microstructures which are basically obtained by conventional optical microscope and then I will show you some analysis by EPSD. So as you see if we under cool the alloy by only 50 degrees that is very small amount you could see the microstructure consisting of grains like this and with which it gained we can see segregation patterns that is basically signature of the solidification at low under cooling and not only that we can see when the dendrites present within the grains and I am marking some of the grains here as you can clearly see here this is another grain and within the grains you can see the dendritic structure built in. So therefore at low under cool solidification happens normally by dendritic manner and as you increase the under cooling level pi more than 100 degree 110 you could see the grain structure much little bit finer than the earlier one and we can also see the segregation pattern inside the grains inside each again with the dendritic morphology remaining in the grain. Now once we do the BST analysis we can find out the nature of this gain boundaries which are there in this microstructure and if you look at it most of the gain boundaries here are shown as a function of misorientation angle number of grains as a function of misorientation angles misorientation basically means a one grain with respect to the other grain is misoriented by certain angle and that is basically the reason for the gain boundary we know that within one grain the orientation of the crystal is same as we cross over the boundary we go to the next grain orientation changes and this orientation change is dependent by misorientation angle in the EBSD. So this data is directly obtained from EBSD after just collecting the EBSD informations and plotted as a number fraction of grains versus misorientation angle as you see most of the grains are actually having misorientation angle more than 25 degrees very small amount is basically having less than 5 degrees so most of the gain boundaries are here high angle grain boundaries that is very clear so therefore one can obtain the nature of the gain boundaries of from the EBSD analysis directly. Now this is the one which I am showing if I under cool by 130 degrees K and you can see in the microstructure there are big grains like this and within the big grain there are small grains this kind of small grains patients so by looking at this optical microgap any what is called avit reader of this what is called microstructure or understand who are having good understanding the microstructure will tell that these grains are actually act formed by some means from the big grains so therefore the boundaries of these grains will be small angle grain boundaries and this big grain boundaries will be large in high angle grain boundaries this is what is we find in main case of doing EBSD if you do EBSD and then find out the misorientation angle plot versus fraction of grains first some gains as a function of misorientation angle you can see that there are large number of grains having misorientation angle less than 15 degrees even in fact if you look at it less than 10 degrees there are large number of grains present so these grains actually are small angle boundary they have the small angle grain boundaries on the other hand there are grains which are having large angle grain boundaries which are present here like the one which I shown you and there is another one I can show you here so that means there is a distinct change of the grain boundary nature of the grain boundaries as the under cooling increases as you know under cooling increases means the ion force persuasion increases that there will be no stress and more stress generation and chances of recrystallization is more so it looks like that these gains which are formed here may be due to recrystallization which will be clear more as I go on if we under cool it even little deeply about 140 K I am just showing you the optical micro guy you can see the big grains here again and within the big grain there are so many small grains present similar nature which I have shown you just one slide before and if you zoom out the picture you can see see this segregation of genetic pattern inside the grains actually if you under cool it even much higher level by 190 K which is very extensively high under cooling you can see that the big grains here present within the big grains there are so many small grains present and a used analysis taken done on this sample it can be represented as a means the number of fraction of grains versus mission and this angle here again you see the large number of grains having less than mission angle less than 10 degrees signifying that they are small angle grain boundaries there are large more molecule can mount is which can be seen here also on the other hand there are also large number of grains which high mission's angle so they are this big grains which are actually so this two things are very clear from this analyst one is that there is a subsequent gain refinement grains are getting smaller as we under cooling increases and at the same time this finer gains are basically having small angle boundaries. So therefore just by doing this every analysis one can tell that these grains most likely has formed by recrystallization and if they have formed by recrystallization obviously they will distincting distincts texture of the material also will be visible. So if I just do a what is called gain map and plot it in different color format we can see there are very large grains you can see this one is a very large grain with pink color and within this large grain there are so many small grains present ever there are small grain presence here and there also and if we get this what is called inverse pole figure you can see this lead this pink grains are very close to 0 to 1 orientation the green actually 0 1 0 1 orientation and the blue little bit blue is grains which are present very small the small ones are actually 1 1 1 orientation very clearly. So you can see the depth of information which one can obtain from one sample by analyzing the EBSD and if you do this again this from the same grain if we if I plot the gain boundary number of fraction of gain boundary versus mission angle again we see large number of grains as a base small mission orientation less than about 7.5 degrees and they are actually having small angle gain boundaries where are there are grains which are having large angle gain boundaries. So gain boundary information very easily obtained now as for this texture is concerned which I just now I mentioned if I just use this and put a plot inverse pole figure from the gain map you can see there is a fiber texture present you can see this kind of nature of this texture clearly present on 1 1 1 orientations in a typical ID was and TD plot and there are obviously orientations of the grains which are predominantly present in along these directions. So one can actually obtain exactly the nature of texture from this analysis and if you do careful analysis that means if we take inverse pole figure of 0 0 1 1 1 0 and 1 1 of this grains or this large number of grains we can actually get an idea of the kind of texture presence you can clearly see that along 1 1 0 directions the picture is much more clear showing the distribution of the orientation of different grains and signifying that there is a distinct texture. So this itself tells us that the grains has formed by recrystallization and there is a texture of the grains present in the sample. So by this way the as I we can actually understand the whole mechanism of gain refinement in a in an alloy where there is no gain refinement presence but because of under cooling gain refinement happens and this was not possible without EBSD obviously one cannot do with the other any other analysis than EBSD because in TM you cannot see so many grains as you have seen the grains are very big so it is not possible to do analysis by transmission electron microscope only possible way do analysis is EBSD. Well so now I am going to basically show you different pictures which different analysis which you have done while giving you the demo in front of the SEM in the Department of Materials Science Engineering at IIT Kanford and here we are looking at another sample of stainless steel austenite stainless steel 316 and as you know it is a basically it is a FCC crystal structure containing about 18% chromium and 8% nickel and one can take the sample and then analyze it again the grains can boundaries misorientations and many other features this sample was basically prepared by simple casting route and followed by rolling and so therefore we expect some curtain kind of what is called recrystallization happened in the during the processing what you see here is basically a gain map of the stainless steel sample and after taking the EBSD data and here I am showing you grain boundaries by plotting different colors okay so if you look at if the grain boundary is having white and then it is a high angle gain boundary the most misorientation will be 15 to 15 to 62.8 degrees that is the basically definition and if the gain boundary is shown by blue color which are there so many large number of grain boundaries are present having gain bound misorientation angles between the grains to be 7.5 to 15 degrees and if it is in the green color it is 7 less than 7.5 degrees so as you can see there are large number of grains having less than 7.5% orientation 7.5 degree orientation differences so that clearly tells us there is some kind of what is called texture first of all there is certain kind of grain refinement happened because of the recrystallization or whatever happened in rolling process now one can actually do this gain map from the EBSD data and that is what shown here you can see even the very clearly the gain map one can even see the twins in the stainless sorry stacking falls in stainless steel this is the one that is another one that is another one that is another one lot of and from the gain map which is very clear gain map one can actually see this pole where 001 111 and 110 FCC is plotted here you can see that this red color grains are again having orientation close to 001 and they are there but not very large on the large number of grain actually green color which have orientation of 101 type. So therefore predominantly the grains are having 101 orientations in this crystal and presence of the grains of what is called 111 orientation is very less and even the grains of 001 orientation is little higher than the 111 orientation but still it is predominantly 101 type of orientation present in the grains now one can actually take the inverse pole figure and analyze the basically pole figure analyze this different texture this is along 111 as you can see here along 110 is not clearly visible what kind of texture is present but along 110 it is very clear that along 110 there are distinct regions where the two orientations are very fixed so there is such a certain amount of texture presence along 111 also you can see clearly this was called predominantly featuring orientation present in the sample in my one can do better nowadays with the help of these better softwares. So what you can see here that the number of grains having different orientation is plotted here this is 001 this is 101 this is 111 and you can see that predominantly the green large number of green areas present here so therefore grains are predominantly 101 which I just now I showed you.