Question

Cu–Be alloys are strengthened by:

• A. Solid solution strengthening
• B. Dispersion strengthening
• C. Grain refinement
• D. Precipitation strengthening

Hint:

Cu–Be alloys are classic examples of \textbf{precipitation-hardened} materials, strengthened via age-hardening treatments.

Answer 1

The Correct Option is D

Step 1: Nature of Cu–Be Alloys
Copper–beryllium (Cu–Be) alloys are non-ferrous alloys known for: - High strength, - Excellent fatigue resistance, - Good electrical and thermal conductivity. Step 2: Strengthening Mechanism
Cu–Be alloys are primarily strengthened by precipitation hardening (age hardening), which involves: - Solution treatment at high temperature to dissolve beryllium, - Rapid quenching to retain a supersaturated solid solution, - Ageing (heating) to allow fine beryllide precipitates (CuBe) to form, - These precipitates obstruct dislocation movement, increasing strength. Step 3: Why Other Options Are Incorrect
- Solid solution strengthening: Present in initial phase, but not the dominant hardening mechanism. - Dispersion strengthening: Involves stable oxides or ceramic particles, not relevant here. - Grain refinement: Affects toughness and ductility more than high-strength enhancement. Conclusion: Precipitation strengthening is the primary mechanism used to enhance mechanical properties in Cu–Be alloys.