稀土元素La对铸造Al-Si-Cu-Mg合金组织及性能的影响OA

The effects of different La contents on the microstructure,mechanical properties,hot tearing sensitivity and fluidity of Al-9Si-1.5Cu-0.4Mg alloy were investigated through equal gradient-controlled experimental method.The results show that the addition of La can significantly refine the alloy grains.The secondary dendrite arm spacings of alloys decrease first and then increase with the increase of La contents.The addition of La improves the eutectic Si modification rate,and the eutectic Si exhibits a coral-like morphology with 0.10%La added.The alloy microstructure consists of primary α-Al,eutectic Si,θ-Al2Cu,Q-Al5Cu2Mg8Si6,and П-Al8Mg3FeSi6 phases.When the La content reaches 0.10%,La-rich phases begin to appear,and the sizes of La-rich phases gradually increase with a higher La addition.When the La content is 0.10%,the comprehensive performance of the alloy is optimal,with room temperature tensile strength,yield strength,and elongation of 364 MPa,219 MPa,and 6.5%,respectively.The hot tearing sensitivity coefficient is 6,which is reduced by 80%compared to the matrix alloy.The flow length is 937 mm,which is increased by 48.0%compared to the matrix alloy.