热处理对低 Cu 含量铸造 Al-Si-Mg-Cu 合金组织性能影响

The effects of heat treatment on microstructure and properties of cast Al-Si-Mg-Cu alloy with low Cu content were investigated by means of optical microscope，SEM and tensile test. The results indicate that the strength and elongation of alloy are increased firstly and then decreased with the extension of solution time，and the eutectic silicon morphology tends to spheroidized. With the extension of aging time at 150 ℃ ，the strength of alloy is gradually increased，and tensile strength reaches 339.87 MPa after aging for 14 h，while elongation presents a trend of decreasing first，and then increasing finally decreasing. At 165 ℃ ，the strength is increased firstly and then decreased with the aging time，which reaches a peak value at 10~14 h，while the elongation is decreased continuously. After heat treatment，W-Al₂Cu₅Si₄Mg₄ and Mg₂Si phases are precipitated，which are dispersed in the matrix，leading to the second phase strengthening and dispersion strengthening，which can improve the strength of alloy and reduce the plasticity toughness.