The temperature gradient describes how temperature changes throughout a material over a given distance. The direction and rate of heat transfer from a hot area of the material to a cooler area are determined by the temperature gradient. Heat flow within a material is determined by the temperature gradient, and the temperature gradient affects the way a material behaves thermally, develops stresses, and performs.

Key Features:

• Heat Transfer Controls: A temperature gradient determines where/how quickly heat flows within a material and, therefore, what temperatures will be found within the material and how quickly any given area will cool.
• Development of Thermal Stress: Non-uniform expansion and contraction cause uneven temperature differences and, therefore, cause thermal stress, which can cause warping, cracking, or both of an object.
• Process Dependence: Manufacturing processes, such as welding, casting, and heat treating, are very much dictated by the temperature gradients present, which then dictate the subsequent microstructure and mechanical properties.

The importance of temperature gradients comes from their relationship to material integrity and performance. When welding takes place, the temperature gradient at or near the weld zone is so steep that it rapidly heats and cools the area, thus causing grain structure changes and weakening of the area. Controlling temperature gradients helps reduce imperfections, such as warping or cracking. In addition, using uniform temperature gradients during heat treating will allow for the hardness and strength of a finished part to be fairly uniform throughout the entire area.