Natural aging
Cold aging is the process where age-hardenable alloys strengthen at room temperature by precipitating out. This increases the strength and toughness of the material.
Physico-chemical Mechanism of Action
During cold aging, the material crystallizes at room temperature and forms precipitates, such as graphite or silicon carbide. These precipitates enlarge the grain structure and affect the mechanical properties.
Metallurgical Relevance & Welding Risks
Cold aging can lead to increased strength and toughness, which is particularly advantageous in heavily loaded components. However, it can also cause grain coarsening, which makes the material more prone to cracking. Incorrect cold aging can therefore lead to an uneven strength profile and material damage.
Workshop Practice & Procedures
To ensure successful cold aging, the right precipitates must be added. This can be achieved by adding alloying elements like silicon or carbon. The time and temperature of cold aging must be precisely controlled to achieve a homogeneous grain structure. Insufficient precipitation can lead to no strength increase, while over-precipitation can cause grain coarsening and possible cracking.