Recrystalization

Abstract

In this experiment C26000 heat treated brass, at different annealing temperatures were tested for hardness and tensile strength. Pictures of samples of C26000 heat treated brass were taken with the help of a microscope. As the temperature of the heat treatment went up so did the size of the grains.

Introduction

This lab dealt with the issues of heat treatments and their affects on a materials structure. The three heat treatments that this lab focused on were stress relieving, recrystallization and softening/ annealing. Stress relieving relieves a material of stress reducing the chance of failure in the future. Stress relieving at the recrystallization temperature is more economical than below the recrystallization temperature, but results in a loss of strength.

Recrystallization focuses on quick change in tensile properties leading to a strain free crystal structure. Softening is applied when a material is expected to go through future cold working. Softening takes place when a material is heated above its recrystallization temperature and is held until the recrystallization is complete.

Procedure

The lab group was divided into three groups and assigned C26000 brass materials that had been treated at various temperatures. After splitting into groups lab groups tested their samples for both hardness and tensile strength. For the hardness test we used the Budlen Hardness tester id # 99567345. For the tensile lab groups used the Instron 4204 until failure of the brass materials.

After testing the hardness and tensile strength of the brass heat treated materials lab group took photos of magnified samples of the heat treated brass materials the lab group had just tested. The samples were magnified with a Nikon Microscope at 20x magnification. The pictures were taken with a camera mounted on the microscope. The camera was a Paxcam. After the photos were taken the lab group observed them and compared to see changes in grain structure.

Results

Here are figure 1 and table 1. Figure one displays the stress vs. strain curves of the different materials. Table 1 exhibits some of the important values dealing with hardness and strength.

AR Brass 250 Brass 350 Brass 450 Brass 550 Brass 750 Brass

Hardness HRF 98.2 98.7 86.6 56.7 48.4 25.8

Yield Strength 450 403 383 169 108 62

UTS (MPa) 562 542 522 450 413 332

Discussion