挤压工艺及La变质对Mg_2Si/Al-Cu原位复合材料组织及性能的影响

Influence of Squeeze Casting and La Addition on Microstructure and Properties of the In-Situ Mg_2Si/Al-Cu Composites

研究了La变质对10Mg_2Si/Al-Cu-xLa(x=0,0.2,0.4,0.8,质量分数)复合材料组织及性能的影响。结果表明,经La变质后,10Mg_2Si/Al-Cu复合材料中共晶Mg_2Si相由粗大的汉字状变为细小的条状或点状,明显细化,其力学性能也得到显著提高。当添加0.8%的La变质时,其硬度(HV)高达133,但组织中存在粗大的针状富La相,导致抗拉强度和伸长率有所降低。通过挤压工艺发现,挤压能显著细化Mg_2Si和针状富La相,提高复合材料的力学性能。尤其是经超声辅助挤压铸造后,10Mg_2Si/Al-Cu-0.8La复合材料的性能最优,其硬度(HV)、抗拉强度和伸长率分别为146、336 MPa和2.5%,比重力铸造的复合材料的性能分别提高了16.8%、22.2%和92.3%。

The influence of La addition on the microstructure and properties of 10 Mg2Si/Al-Cu-xLa(x=0,0.2,0.4,0.8,mass fraction)composites was investigated.The results indicate that the eutectic Mg2Si phase is refined remarkably in the 10 Mg2Si/Al-Cu composites with the addition of La,which is changed from a large Chinese character to a thin strip or dot,and the mechanical properties of the composites are improved.significantly The 10 Mg2Si/Al-Cu-0.8La composites present 133 HV in hardness,however existence of large needle-like La-rich phases leads to the reduction of its ultimate tensile strength(UTS)and elongation.Therefore,the squeeze casting was applied to improve the microstructure and properties of 10% Mg2Si/Al-Cu-0.8La composites.The experiments show that squeeze casting can refine significantly Mg2Si and needle-like La-rich phases,leading to the increase of hardness and mechanical properties.The optimal properties can be obtained in 10 Mg2Si/Al-Cu-0.8La composites prepared by the squeeze casting(SC)assisted with ultrasonic treatment(UT),which exhibit 146 HV in hardness,336 MPa in UTS and 2.5%in elongation,respectively,which are increased by 16.8%,22.2% and 92.3%,respectively,compared with those of ones fabricated by gravity casting(GC).