Saturday , 21 July 2018

What is malleability?

Kedar Kulkarni

“Raju, what is new in school,” asked Raju’s father while having lunch on Sunday afternoon. Raju

Said: “Papa we are learning about mechanical properties of metals. Teacher taught us about malleability and ductility, and I cannot understand malleability.” His father said: “I will explain it to you after lunch.”

After finishing lunch Raju’s father asked his mother to prepare two different types of dough. One made of maida and other of besan. He then gave Raju a small ball of maida dough and asked him to roll it out as a chappati. Raju began rolling and made a very thin sheet with the maida dough.

His father then gave him a ball of besan dough asked him to try rolling that out. Raju began rolling that dough ball but could not even make a small round chappati. The dough was cracking as Raju tried to roll it. He remembered what the teacher had said. “Malleability is a physical property of metals that enables metals to be made in to thin sheets without breaking. In other words, it is the property of a metal to deform under compression.”

He said: “Papa now I understand, the dough made from maida is more malleable than the one made from besan.”

His father said: “Right, just like the maida dough some metals can also be rolled into very thin sheets when rolled between rollers at high pressure. Some like gold can be even rolled as thin as a few microns.

You are familiar with the aluminium foil your mother uses to wrap sandwiches. It is so thin. Some metals cannot be made into thin film, they are less malleable.”

Gold (Au), copper (Cu), tin (Sn), iron (Fe), Aluminium (Al) and Silver (Ag) are malleable metals.

(Writer is an engineer)

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