Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 7: Problem 33

Briefly cite the differences between recovery and recrystallization processes.

Short Answer

Expert verified
Question: Explain the main differences between recovery and recrystallization processes in the context of annealing. Answer: Recovery and recrystallization are stages in the annealing process with different purposes and effects on a metal's properties. Recovery occurs at lower temperatures and involves the rearrangement of atoms within dislocations to relieve internal stresses without significant changes in grain structure. Recrystallization takes place at higher temperatures, forms new stress-free grains, and aims to restore ductility and reduce hardness. Recovery leads to minor improvements in mechanical properties, while recrystallization significantly changes them by increasing ductility and decreasing hardness.

Step by step solution

01

Definition and Purpose of Recovery Process

Recovery is the first stage of the annealing process, which occurs at lower temperatures (compared to recrystallization), and involves the rearrangement of atoms within the existing dislocations in the metal's crystal lattice. The purpose of recovery is to relieve internal stresses in the material induced by cold working, such as plastic deformation, without causing significant changes in the grain structure.
02

Definition and Purpose of Recrystallization Process

Recrystallization is the second stage of the annealing process, which occurs at higher temperatures when compared to the recovery stage. In this stage, new stress-free and defect-free grains are formed, replacing the distorted and dislocated grain structure formed during cold working. The primary aim of recrystallization is to restore ductility and reduce the hardness of the worked material, enabling further cold working or other processes.
03

Changes in Microstructure

During recovery, the existing crystal structure of the material rearranges itself, which results in lower internal stresses, reduction in the density of dislocations, and minimal changes in the grain structure. On the other hand, recrystallization involves the formation of entirely new grain structures with decreased dislocation density and rearranged lattice structures, restoring the material's ductility and reducing hardened properties.
04

Temperature Requirements

Recovery generally occurs at lower temperatures, within a range of 0.3 to 0.5 times the absolute melting temperature of the material (in Kelvin). Recrystallization, however, takes place at higher temperatures, typically between 0.4 and 0.7 times the absolute melting temperature, depending on factors like the degree of deformation, purity, and alloy composition, among others.
05

Effects on Physical Properties

In the recovery stage, internal stresses and dislocation density are reduced, which results in some minor improvements in the material's overall mechanical properties. However, ductility is not fully restored, and the hardness remains relatively unchanged. On the other hand, after recrystallization, the new grain structures provide increased ductility and a decrease in hardness, significantly changing the overall mechanical properties of the material.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

The lower yield point for an iron that has an average grain diameter of \(1 \times 10^{-2} \mathrm{mm}\) is \(230 \mathrm{MPa}(33,000 \mathrm{psi}) .\) At a grain diameter of \(6 \times 10^{-3} \mathrm{mm},\) the yield point increases to 275 MPa \((40,000\) psi ) . At what grain diameter will the lower yield point be \(310 \mathrm{MPa}\) \((45,000 \mathrm{psi}) ?\)

Briefly explain why small-angle grain boundaries are not as effective in interfering with the slip process as are high-angle grain boundaries.

Is it possible for two screw dislocations of opposite sign to annihilate each other? Explain your answer.

A single crystal of zinc is oriented for a tensile test such that its slip plane normal makes an angle of \(65^{\circ}\) with the tensile axis. Three possible slip directions make angles of \(30^{\circ}, 48^{\circ}\) and \(78^{\circ}\) with the same tensile axis. (a) Which of these three slip directions is most favored? (b) If plastic deformation begins at a tensile stress of \(2.5 \mathrm{MPa}(355 \mathrm{psi})\), determine the critical resolved shear stress for zinc.

Briefly explain why HCP metals are typically more brittle than \(\mathrm{FCC}\) and \(\mathrm{BCC}\) metals
See all solutions

Recommended explanations on Physics Textbooks

Nuclear Physics

Read Explanation

Electrostatics

Read Explanation

Medical Physics

Read Explanation

Quantum Physics

Read Explanation

Work Energy and Power

Read Explanation

Torque and Rotational Motion

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free