Heat treatment process and effect evaluation of magnesium forgings in construction machinery

For magnesium forgings of construction machinery, proper heat treatment process can significantly affect its mechanical properties, structure and corrosion resistance. The following is the generally used heat treatment process and its effect evaluation:

1. Solution Treatment: Solution treatment is a heat treatment method that achieves uniform distribution of solid solution in alloy through high temperature heating. In construction machinery magnesium forgings, solution treatment is usually carried out at a higher temperature, such as 480-500°C. Solution treatment can dissolve the solute elements in the alloy and form a uniform solid solution structure. This helps to improve the plasticity, toughness and ductility of the material.
2. Air Quenching: After solution treatment, air cooling is required to cool rapidly and maintain the homogeneity of the alloy structure. The dispersion phase generated during the air cooling process further refines and stabilizes the structure, increasing the strength and hardness of the material.
3. Aging Treatment: Re-aging treatment is a sequential reaction at a lower temperature after solid solution treatment to further refine and stabilize the tissue. Usually, two-step aging treatment is adopted. The first step is initial aging in the range of medium temperature, by precipitating small high-strength phase; The second step is to carry out the final aging in the low temperature range, so that the phase particles continue to increase and improve the strength and hardness. Reaging treatment can also regulate the plasticity and toughness of the material, and improve the fatigue resistance and stress corrosion resistance.

Through the above heat treatment process, construction machinery magnesium forgings can achieve the following effect evaluation:

1. Improve strength and hardness: Appropriate solution treatment and reaging treatment can fine and evenly distribute the phase particles in the alloy, increase the grain boundary strengthening and solid solution strengthening, and effectively improve the strength and hardness of the material.
2. Improve corrosion resistance: solution treatment and air cooling can reduce the defects and impurities on the surface of magnesium alloy and improve its corrosion resistance.
3. Adjust plasticity and toughness: Reaging treatment can adjust the plasticity and toughness of the material to achieve a balance between material strength and ductility.
4. Improve fatigue resistance and stress corrosion resistance: Appropriate reaging treatment can optimize the organizational structure and improve the fatigue resistance and stress corrosion resistance of the material.

It should be noted that each magnesium alloy material has its specific heat treatment process parameters and time-temperature curve, and the specific heat treatment process should be selected and determined according to the material type and requirements. In addition, factors such as cooling rate, temperature control and holding time during the heat treatment process also need to be strictly controlled to ensure that the obtained material structure and properties meet the design requirements.