Semi-Coherent Precipitation
Partially coherent precipitation occurs at periodically arranged dislocations at the interface, partially compensating for lattice misfit. This leads to mixed cohesion between the phases.
How It Works Physically and Chemically
In partially coherent precipitation, the atomic lattices of the two phases aren't completely mismatched – they have regularly arranged dislocations. These dislocations compensate for some of the lattice mismatch, resulting in mixed cohesion.
Metallurgical Relevance & Welding Risks
Partially coherent precipitation can improve joint properties because it creates a continuous phase between the two phases. But it can also cause increased stress buildup if the dislocations aren't optimal. That can lead to cracks or distortion in the weld metal.
Shop Practice & Action Items
To promote partially coherent precipitation, you need to ensure the right composition and temperature curve during welding. You can do that by picking the right alloy and sticking to the specific heat treatment times.