In history, China has always been called equipped cavalry, not heavy cavalry. The Three Kingdoms began to record him. It was not reused in the Tang dynasty, when the powerful Tang dynasty was basically equal to no opponent. Tang Jun's main opponent is light cavalry, Turkish riding and shooting. In contrast, heavy cavalry has obvious defects:

First of all, mobility is not good. The combined weight of armor, knights and weapons and equipment exceeds 100 kg. The weight of the horse is too heavy, and it is difficult for the strongest horse to charge at high speed in this case. So it can only be used to break the array. The battlefield in China is bigger than that in Europe. It is normal for the army to move quickly within hundreds of miles, but it is difficult to heavy cavalry. So it's of little use.

It's too expensive. There are a lot of equipment, which are completely maintained by money, and they are generally unwilling to use them. It costs money, but the effect is not great. It is not cost-effective to use so few scenes. Heavily armored cavalry is mainly used to rush the array. Even if it is successful, there are often heavy casualties. It's really expensive to add new men to every battle.

Weapons have developed rapidly, such as crossbows, which have little advantage in dealing with heavy cavalry. In particular, the range and armor-piercing power of crossbows are getting bigger and bigger, which makes the armor of heavy cavalry lose protection. In the Tang dynasty, crossbows with a range of 200-300 meters were widely equipped, and even crossbows were even available. Seven iron feather arrows can be fired at a time, and the range can reach thousands of meters. These iron arrow are as big as spears used by infantry. If you are shot into the queue of heavy cavalry, it will inevitably cause serious casualties. The progress of bow also makes the protection of heavy cavalry appear insufficient, so we have to increase armor, and the consequence is that the requirements for horses are higher and the maneuverability is worse. On the other hand, infantry also have melee weapons to contain heavy cavalry. The horse-chopping knives in the Tang Dynasty and the strange knives developed later were all used by elite infantry to fight in array, and cavalry could not even break the strange knife array head-on.

I wonder if it will be useful to you? Hope to be adopted.