why does it matter you unlock it or not. Xiaomi supports unlocking bootloader without voiding warranty until it is mentioned in your country specifically that it will void warranty.
Link don`t work, broken!
/* * Your warranty is now void. * * We're not responsible for bricked devices, dead SD cards, * thermonuclear war, or you getting fired because the alarm app failed. Please * do some research if you have any concerns about features included in this recovery * before flashing it! YOU are choosing to make these modifications, and if * you point the finger at us for messing up your device, we will laugh at you. * */