MATERIALS ENGINEERING
ASSIGNMENT 2

By Farhan Yosuf (EAU 0710043) - December 10, 2014
INTRODUCTION

Materials are elementary to the revolution of civilizations, so much that we associate ages with them. From the very basic materials used by the Stone Age civilization such as stone, clay, skins and wood to the Bronze Age where the crucial concept of alloying was formulated to the current age where we have a periodic table, a reference to all the elements discovered, enabling us to achieve the great heights that we currently achieve.
So as an aerospace engineering student, the importance of study and research of strength of materials is without thought a subject of critical essence.
In this document, we have focused closely on the following …show more content…
This phase strengthens the alloys by obstructing the movements of dislocations.
Precipitation Hardening Metallurgy
Solution treatment is a process in which the alloy is heated to a temperature just below the lowest melting point of the alloy system, It is held at this temperature until the base metal dissolves a significant amount of the alloying elements. The next step is rapid cooling of the alloy for maximum retention of the alloying elements in solution as possible and hence produce a supersaturated solid solution. This condition is mostly unstable and hence, heat-treatable alloys are used in this condition.
Most heat-treatable alloys exhibit some age-hardening at room temperature following solution heat treatment. The rate and degree of natural age hardening at room temperature differs between alloys. Alloy 7075 and most other aluminium-zinc-magnesium-copper alloys continue to age harden endlessly at room temperature and are hardly used in naturally aged …show more content…
The feasible range of temperatures for precipitation control is between 120 to 180°C. Variables such as the alloy, the properties desired and production schedule determine the actual temperature.
Soluble alloying elements that exceed the solid solubility limit at room temperature must be present in an aluminum alloy that responds to precipitation hardening. Additionally, the alloy should be able to dissolve the excessive soluble alloying elements and precipitate them as separate constituents within the crystal lattice. The structure of the constituents precipitated must be different from that of the solid solution. Careful control of this precipitation reaction is crucial, otherwise the hardening constituents become too coarse and do not help in the strengthening of the alloy.
Stress-Strain curves of Aluminum in comparison with various metals and