Question

Hot extrusion of aluminium is done in the temperature range of

• A. \(250^\circ \text{C} - 300^\circ \text{C}\)
• B. \(350^\circ \text{C} - 500^\circ \text{C}\)
• C. \(600^\circ \text{C} - 800^\circ \text{C}\)
• D. \(850^\circ \text{C} - 950^\circ \text{C}\)

Hint:

For hot extrusion of aluminium, remember: temperatures should be significantly above its recrystallization point but below melting. \( 350^\circ \text{C} - 500^\circ \text{C} \) is an ideal practical range.

Answer 1

The Correct Option is B

Hot extrusion involves heating a metal above its recrystallization temperature to make it easier to deform plastically. For aluminium, this temperature typically falls in the range of: \[ 0.6T_m \text{ to } 0.75T_m \quad (\text{in Kelvin}), \] where \( T_m \) for aluminium is approximately \( 933 \, \text{K} \) (or \( 660^\circ \text{C} \)). \[ 0.6 \times 933 \approx 560 \, \text{K} \quad \text{and} \quad 0.75 \times 933 \approx 700 \, \text{K} \Rightarrow \text{in } ^\circ\text{C}: \quad 287^\circ \text{C} \text{ to } 427^\circ \text{C} \] Hence, \( 350^\circ \text{C} - 500^\circ \text{C} \) falls within the safe range used for hot extrusion of aluminium, allowing sufficient ductility and reducing the extrusion pressure.