不同Mg/Li比对粉末冶金Al-Mg-Li合金显微组织及力学性能的影响

Microstructure and Mechanical Properties of Powder Metallurgy Al-Mg-Li Alloys With Different Mg/Li Ratios

采用粉末冶金工艺和热挤压方法制备了Al-Mg-Li合金,并通过金相显微镜、扫描电子显微镜、透射电子显微镜和拉伸试验机对合金的微观组织、断口形貌和力学性能进行了分析。研究了不同Mg/Li比(1.3、1.8、2.5)对合金在烧结态、挤压态和T6热处理态下的微观组织和力学性能的影响。结果显示,随着Mg/Li比的增加,烧结态合金的相对密度增加,表明Mg元素对烧结过程具有促进作用。对于挤压态Al-Mg-Li合金,随着Mg/Li比的增加,合金中含Mg的析出相逐渐增多,并聚集在晶界附近,力学性能得到了很大提高,抗拉强度由285 MPa增加至407 MPa。经T6热处理后,Al-Mg-Li合金的第二相主要由δ′相和T相组成,其中δ′相是主要的强化相,均匀分布在铝基体中,而T相在晶界处呈链状分布。研究表明,提高Mg/Li比可以提高Al-Mg-Li合金的抗拉强度和屈服强度,但延伸率可能会有所下降。T6热处理后Al-5Mg-2Li合金可达到抗拉强度532 MPa、屈服强度473 MPa、延伸率4.5%。

Al-Mg-Li alloy was prepared using powder metallurgy and hot extrusion methods.The microstructure,fracture morphology and mechanical properties of the alloy were analyzed using metallographic microscopy,scanning electron microscopy,transmission electron microscopy,and a tensile testing machine.The effects of different Mg/Li ratios(1.3,1.8,2.5)on the microstructure and mechanical properties of the alloy in the sintered,extruded,and T6 heat-treated states were investigated.The results revealed that an increase in the Mg/Li ratio led to an increase in the relative density of the sintered alloy,indicating the promoting effect of Mg on the sintering process.For the extruded Al-Mg-Li alloy,as the Mg/Li ratio increased,the precipitation of Mg-containing phases gradually increased and clustered near the grain boundaries,resulting in improved mechanical properties,the tensile strength of which increased from 285 MPa to 407 MPa.After T6 heat treatment,the second phase in the Al-Mg-Li alloy mainly consisted ofδ′phase and T phase.Theδ′phase,as the main strengthening phase,was uniformly distributed in the aluminum matrix,while the T phase exhibited a chain-like distribution along the grain boundaries.Increasing the Mg/Li ratio enhanced the tensile strength and yield strength of the alloy,but it may lead to a decrease in elongation.For instance,the Al-5Mg-2Li alloy after T6 heat treatment exhibited a tensile strength of 532 MPa,a yield strength of 473 MPa,and an elongation of 4.5%.