It depends on your interest after B.tech in Mechanical Engineering you can go for  M.tech with given below branches

M.tech courses for GATE (ME) students:

1-Mechatronics engineering

2-Robotics

3-Mechanical engineering (all specialized fields, design, thermal, production, material science etc)

Good Luck!

You should choose a branch or specialization according to your interest.

After completing your B.tech in mechanical engineering you can go for below courses-

• Production
• Thermal Engineering
• Energy Systems
• Industrial Engineering
• Petroleum Engineering
• CAD-CAM , Manufacturing