Built-up edge (BUE) formation — which materials are most prone? Under low-to-moderate cutting speeds and small rake angles, built-up edge tends to form when machining which type of material?

Introduction / Context:
Built-up edge (BUE) is an adhered layer of work material that forms on the rake face near the cutting edge. It cyclically grows and breaks off, degrading surface finish and dimensional accuracy. Knowing when BUE is likely helps select suitable speeds, tools, and coolants.

Given Data / Assumptions:

• Low-to-moderate cutting speeds.
• Small rake angle, inadequate cutting fluid, or high friction conditions.
• Typical steels, aluminum, and ductile metals.

Concept / Approach:
Ductile materials tend to weld to the tool at elevated interface temperatures and high pressures. Adhesion and plastic flow promote BUE formation. Increasing speed, using sharper tools and positive rake, or applying effective coolants reduce BUE by lowering contact time and frictional sticking.

Step-by-Step Solution:
Relate BUE to adhesion and plastic flow of the work material.Identify that ductile metals (e.g., low carbon steel, aluminum) exhibit strong adhesion at the tool–chip interface.Conclude ductile materials are most prone to BUE under unfavorable cutting conditions.

Verification / Alternative check:
Increasing cutting speed or improving lubrication typically decreases BUE; surface finish improves correspondingly, which is observed widely in practice.

Why Other Options Are Wrong:
Brittle and very hard materials chip by fracture and are less adhesive; ‘‘tough’’ is vague without indicating ductility; sintered carbides are tool materials, not work materials being machined.

Common Pitfalls:
Confusing BUE with built-in chip breakers or with crater wear; they are different phenomena.

Final Answer:
Ductile material