Chapter 1033 The Power of Computational Materials Science

Just as everyone at Rolls-Royce was figuring out how to reverse-deduce the technology used by China based on the trial production samples.

At the Haofa Group, the characterization and analysis of the crack morphology and formation causes of titanium aluminum alloy cubic specimens have also produced results...

"Mr. Chang, these are the XRD spectra and EBSD phase diagrams of samples with different degrees of completion ranging from 20% to 90%."

Hang Zhibin rushed into Chang Haonan's office and stuffed several pages of test reports, which were still hot, directly into the latter's hands.

Before Chang Haonan could do anything, he turned to one of the pages:

"You can see that on the fractured sections, that is, points 1 and 2, the atomic percentage of titanium and aluminum is close to 2:1, and the presence of chromium and niobium is relatively small, indicating that the γ phase, B2 phase and a2 phase all exist, and the proportions are relatively balanced."

"In the matrix part far from the crack, that is, at points 3 and 4, the ratio of titanium and aluminum atoms is reduced to 1:1. In addition, the contents of chromium and niobium also increase accordingly, indicating that the proportion of a2 phase and B2 increases significantly, while the γ phase decreases accordingly..."

"..."

Under normal circumstances, if one were to be "suddenly attacked" like this and then immediately indoctrinated with a large number of representational results, it would take a while for one to absorb the ups and downs before being able to listen.

Fortunately, Chang Haonan was thinking about this matter at the time, and his ability to read maps was first-class, so he was able to keep up with the other party's thinking.

After Hang Zhibin finished speaking a long paragraph, he went straight to the final conclusion:

"So it can be proved that during the crack formation process, the a→γ+β eutectoid reaction occurred simultaneously at the cracking position!"

"That's right!"

Hang Zhibin nodded quickly:

"It is exactly the same as your previous speculation. As long as the proportion of a2 brittle phase in the alloy can be reduced, the tensile strength inside the material can be increased and the stress generated can be reduced at the same time."

"Our current plan is to preheat the substrate during the molding process. On the one hand, this can inhibit the peritectic reaction and reduce the formation of a2 phase. On the other hand, it can also control the cooling rate to a certain extent."

Compared to his excitement, Chang Haonan's reaction was quite calm.

In fact, a few days earlier, he had improved the crack generation during the drilling process by increasing the temperature of the immersion liquid.

Therefore, this result at most added a layer of theoretical insurance and did not surprise him.

“Substrate preheating is only one aspect. In addition to cracks caused by cooling too quickly, 4722 has another problem during processing.”

Chang Haonan stood up and picked up the thermos from the small table next to him. He poured two cups of water each and handed one to Hang Zhibin in front of him.

"You have just done EBSD and micromorphology observations. You should be able to find that during the forming process of titanium-aluminum alloy, since the local temperature of the molten pool is higher than the evaporation point of aluminum, some of the aluminum-containing gas will evaporate and lose, and those gases that do not have time to evaporate will form small holes during solidification."

"Large residual stress will accumulate near these holes. Although the distribution is not as extensive as the stress caused by cooling, it will also induce cracks in the surrounding areas. And because there are no secondary cracks in the expansion process of this thermal crack, the development of the main crack will be more obvious."

"am I right?"

"Ah... ah?"

Hang Zhibin had just raised his hand in the air, but after hearing Chang Haonan's analysis, he froze in place as if struck by a thunderbolt.

Because this is exactly what he wanted to tell Chang Haonan next.

This is also the most important finding in the report just now.

result……

The other party knew it in advance without even looking at it?

About half a minute later, Hang Zhibin finally reacted and quickly took the cup in his hands:

"This... is this also what you speculated?"

You know, this problem is unique to the thermoforming process.

The cold working process cannot reach the melting point of titanium alloy at all, so it is impossible to observe the phenomenon.

"How can it be……"

Chang Haonan smiled and waved his hand.

"Oh……"

Hearing that Chang Haonan's explanation was the same as his previous thoughts, Hang Zhibin finally breathed a sigh of relief and waited for the other party to explain further.

But before he could catch his breath, he heard Chang Haonan continue:

“I calculated this.”

"..."

Hang Zhibin held the cup, not knowing what expression to use for a moment.

I wanted to lower my head and drink some water to delay the situation, but I forgot that the water was just poured out of a thermos...

Fortunately, Chang Haonan was standing in front of the window with his back to him, so he didn't notice the embarrassing situation that the other party almost burned his tongue, and just continued to introduce his conclusion:

"Through the results of molecular dynamics research, it is found that at higher temperatures, the expansion rate of aluminum oxide is much slower than that of titanium oxide, which has similar thermodynamic stability. As a result, titanium alloys containing aluminum cannot rely on the aluminum oxide film for self-protection like aluminum alloys containing titanium. The chromium and niobium in the 4722 alloy are added as antioxidant elements."

"However, these two elements exist in the matrix alloy in the form of solid solution, which affects the formation mode of aluminum oxide. This determines that in the process of heating-oxidation-melting, aluminum will be more easily lost in the form of gas..."

"..."

When he heard the middle part, Hang Zhibin had already put the cup aside, took out a pen and paper and started recording——

When I first met Chang Haonan, he said that he had studied some computational materials science, which was not a compliment.

Although I didn't really understand it at the time, one thing was very certain.

Traditional materials science analyzes the causes of phenomena, then deduces the laws and generates theories.

However, the research process of computational materials science is the opposite of this.

First there is the theory, then the law is deduced, and finally the phenomenon is obtained.

In other words, although the current application scope of this discipline is still relatively narrow, as long as the application is successful, it means that while discovering the problem, a solution to the problem has also been found.

Just like it is now.

"We will further adjust the forming parameters of laser selective melting to minimize local overheating and reduce the evaporation of aluminum."

Hang Zhibin responded while writing the last few words in the notebook.

Then, retract the pen tip with a click.

“Adjusting parameters is just a stopgap measure.”

Chang Haonan sat back in his chair and said:

"In the long run, as I said earlier, chromium and niobium are added to improve the oxidation resistance of titanium alloys, but even if the temperature is perfectly controlled during the forming process, it will cause the aluminum to concentrate on the upper surface of the final forming, while the content in other parts will decrease, which in turn will have an adverse effect on the oxidation resistance."

"I don't care what kind of coating the British are going to use to solve this problem, but on the one hand, we are completely lacking in this part of information. On the other hand, even if there is a coating, improving the antioxidant capacity of the substrate itself is by no means a bad thing."

Hang Zhibin thought for a while:

"So, you want to improve on this material from the British?"

If the person sitting in front of him was anyone other than Chang Haonan... and Academician Cao Xiaochun, he would have probably thrown his pen on the table -

Materials science is not just about changing the composition or proportions of elements.

Now they are not even sure about the process parameters of 4722, and even need to conduct a lot of experiments to complete the remaining parts.

Thinking about improving the material in this situation is almost like trying to run a marathon before you even learn to crawl.

It's completely a fantasy.

Not only will it fail to achieve the goal of improving performance, but due to insufficient understanding of the original materials, it may even fail to achieve the performance of others before the improvement.

There is a high probability that what you get is pure waste.

However, considering Chang Haonan's actual situation, Hang Zhibin pressed the pen tip out with another click.

"Exactly."

Chang Haonan knocked on the table excitedly:

"I tried a few rare earth elements and accidentally discovered that replacing a certain amount of chromium and niobium with a small amount of ytterbium and cerium can refine the grains, purify the matrix, and improve the adhesion of the oxide film."

"In addition, due to their different solid solution conditions, these two elements, especially ytterbium, can also promote the selective oxidation of Al, thereby reducing the difficulty of local temperature control in industrial production."

As he spoke, he took out the calculation results that had just been delivered a few hours ago from the file box and handed them to Hang Zhibin:

"Of course, I am just providing an idea. You still have to do the specific experimental work, so this is the next research direction."

"As for now... In order to restore the British 4722, you still need to study the process parameters of laser selective melting. I am in a hurry to..."