The Necromancer of Hogwarts

when!

Clear crashing sounds sounded one after another in the cage.

The dementors guarding this floor tried their best to slam forward, but they were still unable to shake the skeleton warrior blocking the corner.

Xiang Yu kept using his teeth, and the white bone teeth hit the railings of the cell one after another. Each time, they would leave a white mark on it and get some iron filings on it.

After releasing nearly ten tooth spells in a row, Xiang Yu stopped moving and looked a little ugly.

The sturdiness of the railings was beyond his imagination.

The spell just hit only a little bit of iron powder on it, leaving a gap the size of a hair on the railing.

If you rely on yourself to cast the tooth spell alone, you may have to cast it continuously for a day to create an opening that you can pass through.

Including the time to recover mana and rest, I'm afraid it will take a week to complete.

By that time, maybe the Aurors from the Ministry of Magic will come back, and it will be too late.

Xiang Yu's eyes searched left and right, passing over the firewood on the ground, and his eyes lit up slightly.

Maybe there is a way?

……

There has been no such noise in the cell for more than an hour. The dementors guarding this floor are not as greedy as before, but they have not left. They still stay at this corner, with a cold breath emanating from them. .

In the cell, Xiang Yu rubbed his palms quickly, and a sharpened piece of wood also rotated rapidly with his palms.

The tip of the log was sunk in a shallow pit dug out of a log, and a small clump of dry hair lay beside it.

Xiang Yu was thankful in his heart: "Fortunately, I used to study materials science, and I also liked watching Island Survival. After so many years, I finally remember some useful knowledge."

"These iron bars are firmly fixed in the upper and lower slots."

"Cast iron has a large coefficient of thermal expansion, so as long as its temperature is raised, it will expand."

"At this time, due to the constraints of the slot, the internal stress of the iron railing will increase. It will be more prone to stress concentration inside it, making it easier to break when it is impacted by external forces."

"This is a mechanical explanation."

"From a material science perspective, rapid cooling after heating will make iron railings more susceptible to damage."

"Fire heating will cause part of the ferrite in the iron railing to transform into austenite. If it is suddenly cooled at this time, a hard but fragile martensite structure will be created inside."

"After this treatment, although the hardness of the material will increase, the brittleness will also increase. To give an inappropriate example, it is like glass. Glass is extremely hard, but very fragile and extremely easy to break."

While Xiang Yu was having many thoughts in his mind, a cloud of smoke came from under the firewood in his hand, and orange-red fire burned on the hair, and then slowly spread to the firewood.

Xiang Yu breathed a sigh of relief and spent nearly an hour raising a strong bonfire under the iron railing.

Peeling, peeling, sparks kept jumping, and heat gradually rose in the prison where Xiang Yu was.

Under the raging flames, the temperature of the iron railings located outside the flames was also rising.

Xiang Yu tried it several times with his hands. After finding that the temperature had reached a stable value, he did not wait any longer.

In the absence of an air box and a heating furnace, the temperature of firewood is not high, and is far inferior to that of an alcohol blowtorch.

Don't wait any longer if the temperature reaches the current level. Otherwise, if the temperature drops slowly instead of suddenly, the iron railings will not be weakened but will be strengthened. Then Xiang Yu will be really dumbfounded.

Xiang Yu has prepared water.

There is a water container in his cell, which contains a little water. Water is still dripping from Xiang Yu's cell, but it is now half full.

When the railing was burning hot, Xiang Yu took a deep breath, grabbed the container and poured a ladle of it onto the iron railing.

laugh!laugh!

There was a hissing sound, and bursts of white gas suddenly appeared on the iron railings. The hot iron railings were rapidly cooled by the water, and due to thermal expansion and contraction, extremely strong stress was generated inside them.

Xiang Yu was also very particular about where he splashed water. He did not splash water everywhere, but sprinkled water unevenly for cooling.

Originally, during quenching, it must be cooled evenly, otherwise some places will be hot and some will be cold, which will easily lead to cracks in the material.

Now Xiang Yu went the other way and took advantage of this to deliberately create defects inside the iron railings.

Taking advantage of this moment, Xiang Yu didn't waste any time. His mana poured out, and bone teeth struck the railing one after another.

when!

when!

A crisp sound rang out in the cell again, and the dementors on this level became violent again and rushed against the skeleton warrior, but they were still firmly intercepted by the skeleton warrior.

Xiang Yu's eyes were fixed on the iron railings.

He has thought of all the ways he can think of. If he can't break the iron railing, Xiang Yu will have no choice but to leave his fate to others to judge.

But luck betrays people, but knowledge does not.

Xiang Yu studied materials science in his previous life, but later changed industries in order to make money. At that time, he didn't even know the use of this knowledge.

He never expected that this knowledge would be used after traveling through time. It could be regarded as a feedback left to him in his previous life.

When the bone teeth bombarded the iron railings, cracks like spider webs spread out, and the effect was hundreds of times better than before.

Xiang Yu bombarded the railings again and again, and consumed all the remaining Dementor ashes on his body, seizing the few vulnerable moments of the iron railings to attack.

Dang!

A minute later, a cross-section crack appeared on the first iron railing.

Under the bombardment of a bone tooth, the iron railing fell to the ground with a clang!

Then came the second one, and then the third one!

Five minutes later, in front of Xiang Yu, he finally opened a hole in the iron railings that had been blocking him!

Xiang Yu took a deep breath and put out the bonfire.

He couldn't wait for the temperature here to drop a little, so he bent over and climbed out of the small opening.

When he bent down and got out of the cell, Xiang Yu finally believed what the high school teachers said back then.

If you learn mathematics, physics and chemistry, you won’t be afraid even if you travel through time.

Finally, after coming to the world of Harry Potter and falling into the devil's gambit, Xiang Yu regained his freedom.

His eyes were deep and he looked at the dementors stuck by the skeleton warriors at the corner of the corridor.

Xiang Yu chanted in a low voice.

"The damage deepens."

Red marks fell on them, transforming them into fragile corpses.

Then a cold light flashed in Xiang Yu's eyes, and pale bone teeth flew out. The skeleton warrior also suddenly erupted, and the bone sickle in his hand drew a trajectory like a crescent moon.

"Go away!"