论文部分内容阅读
在浇注温度700℃、模具温度200℃条件下,通过热裂曲线和凝固曲线测试以及OM、XRD、SEM等手段分析了Ca加入量对Mg-5Al-xCa(x=0.5、1.0、2.0、3.0、4.0、5.0,质量分数,%)合金热裂敏感性的影响。结果表明,当Ca加入量增加到4.0%时,合金的热裂敏感性随着Ca加入量的增加而减小;Mg-5Al-4.0Ca合金的热裂敏感性最小,其热裂敏感性系数仅为0.824;Ca加入量增加到5.0%时,合金的热裂敏感性又出现上升,其热裂敏感性系数上升到0.96。加入适量的Ca会降低Mg-5Al-xCa合金凝固时a-Mg的析出温度,并抑制Mg17Al12相形成,缩小合金凝固温度范围,增加组织中的共晶含量,有利于合金凝固后期的补缩,从而降低合金的热裂敏感性。但加入过多的Ca会增加含Ca脆性相的数量,并使合金组织发生粗化,从而导致合金的热裂敏感性增加。
The effect of Ca addition on the microstructure of Mg-5Al-xCa (x = 0.5,1.0,2.0,3.0) was analyzed by means of hot cracking curve and solidification curve test, OM, XRD and SEM at pouring temperature of 700 ℃ and mold temperature of 200 ℃. , 4.0, 5.0, mass fraction,%) the impact of thermal cracking susceptibility of the alloy. The results show that when the content of Ca is increased to 4.0%, the thermal susceptibility of the alloy decreases with the increase of the amount of Ca added. The thermal susceptibility of Mg-5Al-4.0Ca alloy is the smallest, and the thermal susceptibility Only 0.824. When the addition amount of Ca increases to 5.0%, the thermal cracking susceptibility of the alloy increases again, and the susceptibility coefficient of the thermal cracking increases to 0.96. Addition of proper amount of Ca will reduce the precipitation temperature of a-Mg during the solidification of Mg-5Al-xCa alloy and restrain the formation of Mg17Al12 phase, reduce the solidification temperature range of alloy and increase the eutectic content in the alloy, Thus reducing the thermal cracking sensitivity of the alloy. However, adding too much Ca will increase the number of Ca-containing brittle phases and roughen the alloy microstructure, leading to an increase in the thermal cracking susceptibility of the alloy.