Strengthening Mechanism of Metals

Anything that impedes the free motion and / or generation of dislocations will strengthen the material. There are various methods through which the metals can be strengthened and put to use in our daily practice with lower failure probability.

Introduction

Anything that impedes the free motion and / or generation of dislocations will strengthen the material. A pure metal, either cast or hot-formed is extremely weak, with τy/G = 10-4, with τy = yield strength in shear and G is the shear modulus. These yield strengths are the order of 1000 psi or 6.89 MPa. There are enough dislocations to give lots of easy slip, but not enough to get in one another’s way.
Methods have been devised to modify the yield strength, ductility, and toughness of both crystalline and amorphous materials. These strengthening mechanisms give engineers the ability to tailor the mechanical properties of materials to suit a variety of different applications. For example, the favorable properties of steel result from interstitial incorporation of carbon into the iron lattice. Brass, a binary alloy of copper and zinc, has superior mechanical properties compared to its constituent metals due to solution strengthening. Work hardening (such as beating a red-hot piece of metal on anvil) has also been used for centuries by blacksmiths to introduce dislocations into materials, increasing their yield strengths.

Strengthening Mechanism

Precipitation Hardening

Please check the link below to understand precipitation hardening.

http://www.authorstream.com/Presentation/Renzo-62728-Chap11pt3-Thermal-Processing-Metal-Alloys-Strengthening-Mechanisms-Methods-as-Education-ppt-powerpoint/

Work Hardening, Grain Boundary Strengthening, Solid Solution Hardening

http://www.google.co.in/url?sa=t&source=web&ct=res&cd=1&url=http%3A%2F%2Fwww.cmse.ed.ac.uk%2FMSE3%2FTopics%2FMSE2-06%2FLecture%25207%2520Metals%2520I.pdf&ei=gKbNSb_uOIqMkAWfv9DYCQ&usg=AFQjCNGQ3wZyjS900ArKg3k5U2l_8s3ZOg&sig2=fqq7-HE5ZVrzm2gc8is02w

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