Improving the High Temperature Mechanical Performance of Cu-Cr Composite Induced by Residual Nano-Sized Cr Precipitates

The strengthening effects of Cr on Cu-Cr alloy are severely limited due to the relatively low solid solubility of Cr (0.7 wt.%). Also, the mechanical performance deteriorates severely at high temperature due to the Cr precipitates coarsening rapidly or dissolving in Cu matrix again. Here, the supersaturated solid solution Cu-5 wt.% Cr alloy (S1) with Cr solubility of 0.94 wt.% is achieved by a combination of high energy ball milling with spark plasma sintering. After aging treatment, the dissolved Cr (0.94 wt.%) could precipitate from Cu matrix, and when the aging treated Cu-Cr alloy was tempered to high temperature (≥300 ℃), the Cr precipitates could dissolve into Cu matrix again. Notably, a maximum of 0.7 wt.% Cr precipitates could re-dissolve into Cu matrix. Consequently, under high temperature, the residual fine Cr precipitates (at least 0.24 wt.%) can also act as hard dispersion particles to fix the dislocation, resulting in the mechanical performance improvement of Cu matrix. The excellent hardness of 106.27 HV at 500 ℃ was achieved in the S1 composite, which is 23.14 % higher than that of common sample. Also, the increment in yield strength at elevated temperature deduced from the residual Cr precipitates strengthening ranges from 320.51 MPa to 337.81 MPa