Question

Sinterability of aluminium is poor, because:

• A. Soft nature of powder
• B. Poor compressibility
• C. Presence of inherent oxide
• D. Higher thermal conductivity

Hint:

Aluminium powders form a strong oxide layer that hinders particle bonding during sintering — this is why its sinterability is poor.

Answer 1

The Correct Option is C

Aluminium has inherently poor sinterability due to the presence of a stable oxide layer — aluminium oxide (\( \text{Al}_2\text{O}_3 \)) — on its surface.
This oxide layer is:
- Thermodynamically stable,
- Very thin yet highly protective,
- Difficult to break down during the sintering process.
As a result, it prevents effective metallurgical bonding between particles during sintering, even at elevated temperatures.
Other options:
- The soft nature of aluminium does not hinder sintering.
- Compressibility of aluminium is generally good.
- Thermal conductivity affects heat distribution but is not the primary reason for poor sinterability.
Hence, the dominant factor is the persistent oxide barrier on aluminium powder particles.