Metastable Phases in Powder Metallurgy

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What is the primary outcome of increasing milling time in mechanical alloying?

Formation of impurities from the erosion of the balls

Production of composite materials

Creation of a single bcc phase (correct)

Formation of metastable phases

What is the main disadvantage of electrolytic fabrication technique for producing metal powders?

Inability to adjust particle size and shape

Low purity of the produced powders

High production costs (correct)

Limited to pure metals only

Which phase is formed due to repeated impact and cold welding in ball milling?

Face-centered cubic (fcc) phase

Body-centered cubic (bcc) phase (correct)

Metastable phase

Hexagonal close-packed (hcp) phase

Which metal is not suitable for production using the electrolytic fabrication technique?

Nickel (Ni) Signup and view all the answers

Which process is crucial for producing composite materials via mechanical alloying?

Repeated impact and cold welding Signup and view all the answers

What is the primary issue with powders produced via ball milling?

Low purity due to impurities Signup and view all the answers

What is the main difference between gas jet milling and atomization, according to the text?

The use of molten metals in atomization and solid metal particles in gas jet milling Signup and view all the answers

Which powder fabrication technique is known to have very high production rates?

Atomization Signup and view all the answers

In terms of purity, which method stands out for its high purity levels?

Electrolytic method Signup and view all the answers

Which powder fabrication method allows for a wide range of particle shapes?

Chemical method Signup and view all the answers

What distinguishes gas jet milling from atomization regarding the state of the metal used?

Atomization involves molten metals while gas jet milling uses solid metal pieces Signup and view all the answers

Which powder fabrication method is described as versatile for several materials fabrication?

Chemical method Signup and view all the answers

What is the main purpose of ball milling in the context of powder formation?

To create ultrafine and nano-powders Signup and view all the answers

How does impact stress vary with particle size during milling?

Decreases with larger particles and increases with smaller particles Signup and view all the answers

Why are nanomaterials considered metastable?

As they possess different structures at the nanoscale than at the bulk scale Signup and view all the answers

In powder metallurgy, what is the significance of mechanical alloying?

To induce metastable phases like metallic glasses Signup and view all the answers

What effect does decreasing particle size have on impact stress during milling?

Increases impact stress due to higher energy requirement for fracture Signup and view all the answers

Why are metallic glasses considered metastable phases in materials science?

Due to their unstable atomic arrangements despite being solid Signup and view all the answers