Chapter 1033 The Power of Computational Materials Science

Just when everyone at Rolls-Royce was wondering how to reversely deduce the technology used by China based on trial production samples.

Haofa Group has also produced results on the characterization analysis of the crack morphology and formation causes of titanium-aluminum alloy cubic specimens...

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

Hang Zhibin hurriedly rushed into Chang Haonan's office and put several pages of test reports that were still steaming on the paper directly into the latter's hands.

Before Chang Haonan could take action, he turned directly to one of the pages:

"You see, on the section where the fracture has occurred, that is, point 1 and point 2, the atomic percentage of titanium and aluminum is close to 2:1, and the presence of chromium and niobium is small, indicating that the γ phase, B2 Both phase and α2 phase are present, and the proportions are relatively balanced.”

"In the part of the matrix that is far away from the crack, that is, at points 3 and 4, the ratio of titanium and aluminum atoms decreases to 1:1. In addition, the content of chromium and niobium also increases accordingly, indicating that at this time The proportion of α2 phase and B2 components increased significantly, while the γ phase decreased accordingly..."

"..."

If we were to leave it alone, if we were "surprised" like this and then immediately instilled a lot of representational results, we would have to wait for a while before we could hear them.

Fortunately, Chang Haonan was already thinking about this matter at the moment, and his own ability to read pictures was first-rate, so he could follow the other party's thinking.

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

"So it can be proven that during the crack formation process, the eutectoid reaction of α→γ+β occurs simultaneously at the cracking position!"

"That's right!"

Hang Zhibin nodded quickly:

"It is completely consistent with your previous speculation. As long as the proportion of α2 brittle phase in the alloy can be reduced, the tensile strength inside the material can be increased and the stress generation can be reduced at the same time."

"Our current plan is to preheat the substrate during the molding process. On the one hand, it suppresses the peritectic reaction and reduces the generation of α2 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 dull.

In fact, a few days ago, he had improved the formation of cracks by increasing the temperature of the immersion liquid during the drilling process.

Therefore, this result can be regarded as adding a layer of theoretical insurance at most, and it will not surprise him.

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

Chang Haonan stood up as he spoke, picked up the thermos from the small table next to him, poured two glasses of water into each, and then handed one of them to Hang Zhibin in front of him:

"You have just conducted EBSD and micromorphology observations, and you should be able to find that during the titanium-aluminum alloy forming process, because the local temperature of the molten pool will be higher than the evaporation point of aluminum, some of the aluminum-containing gas will evaporate and be lost, and Those gases that don’t have time to evaporate will form small holes when they solidify.”

"Large residual stresses will accumulate near these holes. Although the distribution is not as extensive as the stress caused by cooling, it will also induce cracks around it, and because this kind of hot crack does not produce secondary cracks during the expansion process, the main crack will The development will be more obvious.”

"Am I right?"

"Ah...ah?"

Hang Zhibin had just raised his hand in the air, but when he heard Chang Haonan's analysis, his whole body froze in place as if he had been hit by a thunderbolt.

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

It 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 reacted and quickly took the cup into his hand:

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

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

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

"How is it possible..."

Chang Haonan smiled and waved his hand.

"oh……"

Hearing that Chang Haonan's explanation was the same as what he had just thought, Hang Zhibin finally breathed a sigh of relief and waited for further explanation.

But before he could take his next breath, Chang Haonan continued:

"I calculated this."

"..."

Hang Zhibin held the cup and didn't know how to respond for a while.

I wanted to lower my head and drink water as a strategy to delay, but I forgot that the water had just been poured from the thermos bottle...

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

"Through molecular dynamics research results, at higher temperatures, the expansion rate of aluminum oxide is much slower than that of titanium oxide with similar thermodynamic stability. As a result, titanium alloys containing aluminum cannot rely on oxidation like aluminum alloys containing titanium. The aluminum film is used to protect itself, and the chromium and niobium in the 4722 alloy are added as antioxidant elements. "

“But these two elements exist in the matrix alloy in the form of solid solution, thus affecting the generation mode of alumina, which determines that during the process of heating-oxidation-melting, aluminum will be more easily lost in the form of gas... "

"..."

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

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

Although I didn’t really study it well at the time, one thing was very certain.

Traditional materials science is based on analyzing the causes of phenomena and then working backwards to summarize the rules and then generate theories.

The research process of computational materials science is the opposite of this.

First there are theories, then laws are deduced, and finally phenomena are 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 a problem has been discovered and a solution to the problem has been found.

Like now.

"We will further adjust the forming parameters of laser selective melting to minimize local temperature rise, which causes aluminum to be evaporated."

Hang Zhibin wrote the last few words in the notebook while responding.

Then, retract the pen tip with a click.

“Adjusting parameters is just a stop-gap measure.”

Chang Haonan sat back in his chair and said:

"In the long run, as I just said, chromium and niobium are added to improve the oxidation resistance of titanium alloys. However, even if the temperature is controlled perfectly during the molding process, the aluminum will be concentrated on the upper surface of the final molding. The content of other parts is reduced, which in turn has an adverse effect on antioxidant properties.”

"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 missing this part of the information. On the other hand, even if there is a coating, it is not a bad thing to increase the antioxidant capacity of the substrate itself."

Hang Zhibin thought for a while:

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

If there were anyone sitting in front of him except Chang Haonan...and Academician Cao Xiaochun, he would have probably dropped his pen on the table——

The study of materials is not just about changing the element composition or the ratio.

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

In this case, just thinking about improving materials is almost equivalent to trying to run a marathon without even learning to crawl.

Totally whimsical.

Not only does it fail to achieve the purpose of improving performance, but it may even fail to achieve the performance that others had before improvements due to insufficient understanding of the original materials.

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

However, considering Chang Haonan's actual situation, Hang Zhibin clicked again and pressed the pen tip out.

"Exactly."

Chang Haonan knocked on the table with excitement:

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

"In addition, due to 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 sent a few hours ago from the file box and handed them to Hang Zhibin:

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

"As for now...in order to restore the British 4722, you really still have to dig into the process parameters of laser selective melting. I am in a hurry..."