Welcome back, we're going to be showing a video today or a couple of videos pieced together that help to understand the difference between diffusional and diffusionless transformations. And this is really the result of an old terminology that people have used, that refer to as civilian and military transformations. And as you would expect from the comparison between civilian and military that the civilian would be a bit more random, the military would be organized and we'll see this in that series of clips. In this clip, we're looking at a crowd just meandering around. There's no particular direction in which these people are needing to go. It's only up to the individuals and this would, in effect, be a homogeneous solution in which we have random motion of atoms. So, that's what were seeing in this particular clip. Now what we have is mass flow in a particular direction and what we're seeing is the group is going from left to right making a turn, it's reasonably organized. It's going in a particular direction, but this is still a not completely organized parade. Now, what we're looking at is a clip of Marine Core who are marching and what we see as is a very uniform and a very precise motion of all the individuals that are in the video. In order to see how these two types of transformations occur, we're going to look at an animation. But before we look at the animation, I'd like to be able to describe what actually occurs when the soldiers in the previous video were going from one direction and changing direction and going to another. What we have here on the screen is a still of helmets that are marching onto the Georgia Tech field for the football game and what we're seeing then is a group, which is referred to as a platoon. And what we mean by a platoon is, it is a group of soldiers that are organized into a basic unit. And if we have several of those platoons, we form a company. Now, the platoon is made up of individuals and the individuals form something we refer to as a squad. So the squad are the five individuals that make up the squad, then we have the individual. So we have the individual, we have the squad, we have the platoon and we have the company. So, all of these people are on the field and they're marching. And when we see the animation, what's going to happen is they're coming from the top, going to the bottom and they're taking a turn before they run out of field. So, here's the picture that we have. The first group of individuals have been given the order to take a column left. And so what happens in that column left, the first individual as indicated by the arrow. That individual turns direction and remains in place. So in effect, marches in place, then when we look at the second individual along that front line. That individual has moved up to, so that he is now in line with the first individual who turned. And we continue to do that and look at the arrows, which indicate how far the individual has to move to move to the front line. And of course, what you see, the further out you are from that pivot point, the faster you have to move. So as a consequence of that, the breadth of the lines that are in the platoon will be controlled by how long it takes to move from your original position along the straight line to your new position as you begin to turn. And once everybody has gotten on line, then what we see is the unit marches forward and that's what we get. So, let's watch this video of the animation of the marching helmets. You can see the first platoon coming onto the field, they've executed a turn. The next platoon is coming along and it's executing the turn at exactly the same place. And the last platoon is doing exactly the same thing. So we're in the middle and completing a turn, and you can see that we wind up pivoting at exactly the same place. That person who is on the far side or the far corner right here, this person pivots and faces the direction. This next one comes from his original position and comes up on to this line. And then eventually, what happens is they begin to move forward when they're all along a straight line. So what's happened in effect is, it's like a sheer. We can see these individuals coming along this direction here, like we see in the shear of atoms that are occurring in the martensitic transformation and we're going to see that as we go through the various sections of heat treating steel. Thank you.
