Final answer:
The primary objectives of heat treatment usually include increasing hardness, enhancing electrical conductivity, and reducing ductility. Improving corrosion resistance is less commonly a direct goal of heat treatment.
Step-by-step explanation:
The usual objectives of heat treatment include a variety of goals depending on the material and the desired properties after treatment. For this question, the three best answers are:
- b) Increase hardness: Heat treatment is commonly used to increase the hardness of a material, making it more resistant to wear and deformation.
- c) Enhance electrical conductivity: Although heat treatment is less commonly used for this purpose compared to the first two objectives, certain heat treatments can modify the microstructure of a material, resulting in enhanced electrical properties.
- d) Reduce ductility: Ductility, the ability to deform under tensile stress, is often decreased as a byproduct of increasing a material's hardness through heat treatment.
Improving corrosion resistance, although possible through heat treatment, is often achieved through material selection and coatings rather than heat treatment itself.