Question

A material used for extrusion purpose must possess the following mechanical property:

• A. Ductility
• B. Elasticity
• C. Plasticity
• D. Brittleness

Hint:

For any metal forming process (rolling, forging, extrusion, drawing), the key enabling property is plasticity. The goal is to permanently change the shape, so the material must be able to flow without breaking.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Extrusion is a metal forming process where a workpiece is forced to flow through a die of a desired cross-section. This process involves immense compressive and shear stresses that cause the material to undergo severe plastic deformation. The question asks for the essential property that allows a material to be shaped this way.

Step 2: Detailed Explanation:
Let's define the properties listed in the options:

• (A) Ductility: This is the ability of a material to deform plastically under tensile stress, for example, being drawn into a wire. While related, it's a specific case of plastic deformability.

• (B) Elasticity: This is the ability of a material to return to its original shape after the deforming load is removed. This property is overcome in extrusion; permanent shape change is the goal.

• (C) Plasticity: This is the ability of a material to undergo large, permanent, non-recoverable deformation without fracturing when a load is applied. This is the fundamental property that allows metals to be shaped by processes like extrusion, forging, and rolling. The material must be able to "flow" into the new shape.

• (D) Brittleness: This is the tendency of a material to fracture with little to no plastic deformation. It is the opposite of the required property. A brittle material would simply break under the high pressures of extrusion.
For a material to be successfully extruded, it must be able to withstand large amounts of permanent deformation without failing. This property is best described as plasticity.

Step 3: Final Answer:
The essential mechanical property for a material to be used in extrusion is plasticity, which is its ability to undergo significant permanent deformation.