1、 The Core Influence of Heat Treatment on Different Properties
1. Mechanical performance regulation
① Balancing strength and elongation
Conventional annealing: significant increase in elongation, but decrease in yield strength;
Solid solution aging treatment: yield strength increased by more than 20%, but elongation loss was significant;
Hot isostatic pressing: eliminates porosity defects and increases fatigue strength to 90% of traditional forged parts;
② Optimization of fatigue performance
The HIP+annealing combination process can simultaneously suppress porosity and coarse grain boundary defects, increasing fatigue life by 3-5 times;
Rapid heat treatment refines beta grains to below 10 μ m, increasing fracture toughness by 30%.
2. Corrosion resistance and microstructure
Sedimentary state: fine needle shaped α+β basket tissue, optimal;
Time treatment: coarsening of alpha phase and increasing proportion of beta phase;
Water cooling after aging: a mixture of coarse and large layers of alpha and fine needle like alpha.
2、 Contradictory points in the selection of heat treatment processes
1. Organizational Stability Challenge
Heat treatment above 600 ℃ can easily lead to the enrichment of alpha phase at grain boundaries, forming fatigue crack sources;
Improper cooling rate leads to an increase in residual stress and exacerbates the risk of deformation.
2. Strength plasticity inversion relationship
Annealing improves plasticity but sacrifices strength, while solution aging enhances strength but reduces elongation;
Although HIP treatment improves fatigue performance, it reduces tensile strength by 8% -12%.
3、 Performance oriented heat treatment scheme
1. Aerospace components
Preferred process: HIP+low-temperature annealing.
Goal: Eliminate 99.9% of pores, fatigue strength>900MPa
2. Biological implants
Step heat treatment:1. Solution treatment → 2 Timeliness processing，Balance strength and biocompatibility
3. Marine corrosion-resistant structures
Avoid aging and water cooling: Prioritize using sedimentary or low-temperature annealing to maintain the corrosion resistance of fine grain structure.
