稀土Nd对铸造Al-Si合金低温拉伸断裂行为的影响

Effect of rare earth Nd on tensile fracture behavior of cast Al-Si alloy at low temperature

研究了稀土Nd元素对Al-7Si-0.3Mg合金的低温拉伸性能及其断裂行为的影响。结果表明拉伸温度对铸造Al-7Si-0.3Mg的拉伸性能有显著影响,在低温(-60℃)下拉伸,合金的强度提高但伸长率降低。随着Al-7Si-0.3Mg合金中Nd含量的增加,合金在低温(-60℃)下的屈服强度、抗拉强度和伸长率呈现先升高后降低的趋势。Nd元素含量为0.2wt.%时合金力学性能达到最高值,这是由于Nd对组织细化和Si相的变质作用;当合金中Nd含量分别大于0.4%和0.8%后,组织中会形成棒状Al4Nd相和片状Al2NdSi2相,这些脆性相在拉伸时割裂合金基体,使合金的低温拉伸性能降低。

The effect of rare earth Nd element on tensile properties and fracture behavior of Al-7 Si-0.3 Mg alloy at the low temperature has been studied.The results show that Al-7Si-0.31 Mg alloy with adding Nd element,the yield strength,tensile strength and elongation of the alloy at low temperature(-60℃) showed a tendency that rising first then declining.When the content of Nd element is 0.2 wt.%,the mechanical properties of the alloy reach the highest value,which is due to the effect of Nd on microstructure refinement and Si phase modification.When the content of Nd in the alloy is greater than 0.4% and 0.8%,Al4 Nd phase and flake Al2NdSi2 phase will be formed in the matrix.These brittle second phases split the alloy matrix during tensile process,which reduced the low temperature tensile property of the alloy.