Monel Metal — Composition Identification Monel is a corrosion-resistant engineering alloy commonly used in marine and chemical environments. Its principal constituent combination is:

Introduction / Context:
Trade-name alloys are frequently tested in materials exams. Monel is one of the oldest and best-known nickel-base alloys, valued for outstanding corrosion resistance in seawater and many chemicals.

Given Data / Assumptions:

• Classical Monel compositions are approximately 60–70% Ni and the balance Cu, with minor Fe, Mn, and others.
• Applications include pump shafts, valves, and heat exchanger components in corrosive services.

Concept / Approach:
Monel’s corrosion resistance stems from its high nickel content combined with copper. Unlike stainless steels (which rely on chromium), Monel contains little or no chromium; passivation arises from the nickel-rich matrix. Identifying the primary alloying pair is the key.

Step-by-Step Solution:
Recall composition: Ni–Cu base.Eliminate chromium-containing options; Monel is not a Cr-bearing stainless alloy.Select nickel and copper.

Verification / Alternative check:
Material data sheets list Monel 400 as ~67% Ni, ~31% Cu, with small Fe and Mn, confirming Ni–Cu basis.

Why Other Options Are Wrong:

• Nickel–chromium or Ni–Cr–Fe: these are stainless/superalloy families, not Monel.
• Copper–chromium or copper–tin: bronzes and specialty copper alloys, not Monel.

Common Pitfalls:
Assuming any corrosion-resistant alloy must contain chromium; Monel demonstrates excellent resistance without chromium.

Final Answer:
nickel and copper