What is Dislocation?

It is well known that the actual strength of a crystal is much lower than its theoretical strength.

The so-called actual strength of the crystal is the critical slitting stress of the single crystal measured by the experiment, which is generally 10-4~10-8G, and G is the shear modulus of the crystal. The theoretical strength is the strength calculated according to the rigid slip model of the complete crystal.

Previously, the rigid slip model of crystals was accepted, but it was later found that the theoretical strength of crystals was at least three orders of magnitude higher than the actual strength.

The huge difference between theoretical and practical strengths has forced people to abandon the rigid slip model of intact crystals.

It is speculated that there must be some kind of defect in the crystal, which not only causes stress concentrations, but also that the atoms in the defect area are in an unstable state and therefore move easily.

In this way, the slip process of the crystal is that the local slip first occurs in the defect, and then the local slip area expands.

And this defect that causes local slippage is called dislocation!

It may seem that dislocation is just a small defect in the material, but in fact it is very useful, and it can be said that it is a bottomless subject to continue to study.

Dislocation affects the work hardening of crystals, and the annealing and softening of metal ash is also related to dislocations, which can reduce the elastic modulus of crystals, increase internal friction, and affect the strengthening of alloys.

If the dislocation can be controlled, then the actual strength of the crystal can be greatly improved, and the gap between its theoretical strength and the theoretical strength can be narrowed.

This is Mu Jingchi's current scientific research path.

As these master's students thought, dislocations are really complex, and they study the motion of atoms. Atoms simply cannot be manipulated by humans, so dislocations are complex and difficult.

If it was Mu Jingchi in the past, he would never challenge such complex theories and topics, and honestly follow the direction of his mentor.

But Mu Jingchi, who has already accommodated "Fundamentals of Materials Science (2069 Edition)", already has this qualification.

In the future of 2069, the dislocation theory has developed somewhat deeply.

And it all comes down to one person, Thompson.

He has a very in-depth study of dislocations, published many theories about dislocations, and finally even used a dislocation equation to connect all dislocation theories to construct a complete system of Thompson's dislocation theory.

That equation is also known as the Thompson dislocation equation.

These are now attributed to Mu Jingchi.

In order to develop a new type of high-strength aluminum alloy in the existing pattern, then this dislocation theory system is necessary. Without the support of this dislocation theory system, even if it is explained by luck, it seems shocking.

It's also inconvenient, and every material development can't be explained by luck, right?

"Okay, you'll all have this plan. ”

Because this is just an experimental plan, it is a bit rough compared to a special and detailed paper. Mu Jingchi quickly finished reading the content, "In the past few days, you are not in a hurry to do experiments first, first find monographs and literature on dislocation to read, and analyze it in combination with my experimental plan." ”

"When you're ready, we'll use experiments to verify and analyze. ”

It is impossible for any theory to be used immediately, and that is unreasonable. And how the theory came about also needs to be supported by data display, which is not at all ambiguous.

What Mu Jingchi has now brought out is the theory I in Thompson's dislocation theory system.

This theory has already been verified in 2069, so it is presented directly in the textbook, in the form of a theorem. As for its origin, how Thompson discovered it, and how he verified it, nothing is known.

And this is what Mu Jingchi needs to do now, and it is also what he is preparing to do in his next scientific research.

If the development, verification and preliminary application of this theory are all completed by Mujingchi, then this becomes Mujingchi dislocation theory I. Then there will be II., III., IV., V.

It can be said that the general direction of Mu Jingchi's project is the research and development of high-performance aluminum alloy, but in fact, it is the construction of the dislocation theory system.

After assigning tasks to the four master's students and instructing Ai Xiaosheng, Mu Jingchi ended the discussion.

···

"You're too sketchy here. ”

In the office next to Mu Jingchi's new office, which is Professor Tian's office, he is learning from Professor Tian as a listener and learner.

"You can't pace teaching according to your train of thought, you have to put yourself in their shoes and think about their receptivity and ability to learn. ”

Professor Tian still has a lot of ideas about Mu Jingchi's teaching PPT.

It is undeniable that Mu Jingchi has sorted out the content and knowledge of this lesson plan on "Fundamentals of Materials Science" in an orderly manner, grasping the connection between knowledge, so that students can review old knowledge when learning new knowledge.

But it's just too simple.

For Mu Jingchi, a genius, there is naturally no pressure to learn, whether it is the absorption of new knowledge or the tandem of old knowledge, it can be done very well.

However, for the average student, it is a little difficult to have a lesson plan that is too simple and a way of thinking that is too divergent.

Even in Huaqing University, there are different levels of students who are top students.

"Okay, Professor, I see. ”

Mu Jingchi nodded frequently, he still listened to Professor Tian's guidance, and did not think highly of himself. In the teaching area, he is still new, and he follows the instructions of the big guy, which is very time-saving and energy-saving.

After all, he is still very short of time and energy, and he still needs to keep an eye on the subject project.

"You have a good grasp of the content, and you have a clear and targeted view of what is important. However, the pace of teaching may not be clear without actually attending classes, so it is too simplistic and diffuse in many places. ”

"It's not a big deal, just follow me for a few lessons. ”

Professor Tian is still encouraging Mu Jingchi, and as a teaching assistant, he has done a good job.

"I'll go back and change it. ”

···

"Mom, why are you here? ”

Song Xiaoyi opened the door for her mother, "Didn't you say that you would stay at home for a few more days and accompany your father?"

Song's mother pushed her luggage into the room, then closed the door with one hand.

"Aren't I afraid that you won't be used to living alone?"

"No, the fish have been living with me for the past few days, and they just left today. Song Xiaoyi poured water and handed it to her mother, "You and I are here in Yanjing, aren't you afraid that my father will be alone at home?"

"Otherwise, you should go back to your hometown to accompany your father. Song Xiaoyi persuaded her mother, "I'm in the second semester of my junior year, and I'm about to graduate." You're not worried about me, are you?"

She didn't know Mu Jingchi before, and she didn't have any love behavior, so she wasn't worried at all.

But now, if she wants to pursue Mu Jingchi, then her actions and habits will definitely change, and if she continues to live with her mother, it will be easy for her mother to find out the clues.

Therefore, Song Xiaoyi persuaded her mother to return to her hometown.