Effects of high pressure heat treatment on microstructure and mechanical properties of aluminum bronze

In this study, the effect of high pressure during heat treatment on aluminum bronze alloy was studied. The results showed that high pressure heat treatment had a great impact on the refinement of cast microstructure. Compared with as-cast condition, high pressure heat treatment can refine the grains of aluminum bronze, and the smallest grain size was obtained under pressure 2 GPa for 20 min and 700 °C. Also, the high pressure heat treatment had an effect on the mechanical properties, it showed that the hardness was increased from 205 HV to 218 HV with the pressure increased from 1 to 4 GPa, while the compressive strength was reduced from 964 MPa to 880 MPa. According to theoretical analysis, high pressure can provide grains refining, resulting in the improvement of hardness. However, extremely high pressure may cause high residual stress, leading to the decline of compressive strength. Thus, after 2 GPa pressure heat treatment, a further heat treatment at 600 °C for 2 min was applied. The hardness increased to 207 HV and the compressive strength increased to 1358 MPa, showing an increase by 11.29% and 24.70%, respectively, compared with that of the as-cast aluminum bronze. (paper)