Heat treatment process is an essential part of design and manufacturing. Heat treatment can change materials behavior, so that they can be used under different condition. In general, heat treatment applied to all three types of basic materials: ceramic, metal and polymer. Therefore, knowing heat treatment process is very important in industry. In this experiment, the purpose is to understand how heat treatment changes materials behaviors. And also understand the difference in materials properties under different heat treatment processes.
The first part of this experiment is heat treatment process. As mentioned, heat treatment is important in industrial processes today. Heat treatment is done by heating up the material, then cool it to room temperature in general. It is important because it can alter the mechanical properties and also the microstructure of a material, such as ultimate strength, toughness, hardness ductility and etc. Therefore, a heat treating material will be more capable to withstand extreme condition than a normal material.
There are four major types of heat treatment processes, which are annealing, normalizing, quenching and tempering. For annealing process, the material is heated to its annealing temperature, hold for at least one hour, then it is cooled in a furnace with a very slow cooling rate like 0.5 degree Celsius per minute. For normalizing and quenching processes, the material will be heated to its austenitic temperature range, also hold at this temperature for at least one hour. However, their cooling rate is different. Normalized materials will be air-cooled. Quenched material will be cooled in a rapidly rate, usually is water quenching. For tempering process, it is the same process as quenching treatment, but the material will be reheated to about 400 degree Celsius after quenching, hold for about 30 minutes, and air-cool at the end.
Here is the phase diagram of steel alloy. A phase diagram is really important for heat treatment process because it shows the microstructure and phase of material in different temperature. Like in this experiment, 1045 steels were test in different heat treatment processes. The composition of 1045 steel is about 0.45 percent carbon. From this diagram, the austenitic temperature range for 1045 steel is about 800 degree Celsius to 1400 degree Celsius. And the annealing temperature is about 723 degree Celsius.
The second part of this experiment is tension test. The purpose of tension test is to measure material’s tensile strength and deformation under a uniaxial tensile load. Also, the tensile behavior and mechanical properties will be determined. Therefore, the heat treating materials will be used to perform tensile test until failure occurs. And the change and difference of tensile behavior and mechanical properties will be studied.
In order to minimize the geometrical factor involved with the results of a tensile test, the loading and deformation are converted to engineering stress and engineering strain. All results of
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