This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Dispersion Hardening”.
1. Dispersion hardening is a type of ____
a) Second phase particle strengthening
b) Strain hardening
c) Solid solution hardening
d) Precipitation hardening
Explanation: Dispersion hardening is a type of second phase particle strengthening. The second phase is mechanically alloyed in matrix. While precipitation hardening is another type of second phase hardening.
2. Which shape is preferred in dispersoids?
b) Plate like
c) Needle like
Explanation: Spherical shape is preferred in dispersoids. This is because, spherical shape causes least cracking possibilities. Needle-like shape particles may cause notch like effect.
3. Which dispersoid is usually added in copper?
Explanation: Copper is generally strengthened by alumina dispersion. This strengthening improves its mechanical properties. Alumina is added in aluminium also.
4. Which dispersoid is mostly used in stainless steel?
Explanation: Stainless steel is dispersion strengthened by TiB2. This improves steel’s mechanical properties at elevated temperatures.
5. Which dispersoid is added to tungsten matrix?
Explanation: Tungsten is strengthened by thoria dispersoids. This is used in bulb filaments. It checks the grain coarsening.
6. What is aluminium’s recrystallization temperature when strengthened with alumina dispersoids?
b) 0.3 Tm
c) 0.6 Tm
d) 0.9 Tm
Explanation: Dispersoids improve high temperature properties of alloys. These increase recrystallization temperature of alloy. In the case of aluminium with alumina strengthened, it raises up to 0.9 Tm.
7. Dispersoids get coarsen on high temperatures.
Explanation: Dispersoids are incoherent particles. Therefore, these do not get coarsen at high temperatures. That’s why these have high temperature properties.
8. Dispersoids are ____ particles.
a) Fully coherent
b) Semi coherent
c) Partial coherent
Explanation: Dispersoids are incoherent particles. While precipitates are coherent particles. That’s why dispersoids don’t get coarsen on high temperature.
9. Dispersion particles should not be _____
Explanation: Dispersion particles are chosen such that their hardness is higher than the matrix. These should be numerous. The spherical shape is preferred.
10. Dispersion hardened alloys show _____
a) Low yield strength
b) High ductility
c) High strain hardening rates
d) Poor high temperature properties
Explanation: Dispersion hardened alloys have good strength and hardness. These retain these properties even at high temperatures. These show high strain hardening rates.
11. Dispersion hardened Systems are limited.
Explanation: Unlike precipitation hardening, dispersion hardening has no such limitation of decreasing solubility with decreasing temperature. So there can be an infinite number of dispersion hardened Systems.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
To practice all areas of Mechanical Behaviour & Testing of Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.