高温处理后闭孔泡沫铝压缩性能及变形机理

Compressive Properties and Deformation Mechanism of Closed-cell Aluminum Foam with High Porosity after High Temperature Treatment

目的探究温度和孔隙率对闭孔泡沫铝材料压缩力学性能和变形机理的影响。方法将孔隙率为84.3%~87.3%的泡沫铝试件在温度25~700℃内进行加热处理,对处理后的试样开展准静态压缩实验。结果在准静态压缩条件下,闭孔泡沫铝材料在不同温度加热处理后的压缩应力-应变曲线均经历了3个阶段:弹性阶段、塑性平台阶段和密实阶段。孔隙率从87.3%减小到84.3%时,其弹性模量增大了44.4 MPa,屈服强度增大了0.39 MPa,平台应力增大了0.94 MPa。孔隙率为84.3%的泡沫铝,在25℃时,其弹性模量为141.4 MPa、屈服强度为4.25 MPa、平台应力为4.75 MPa;当加热温度为500℃时,弹性模量减小到了128.0 MPa、屈服强度减小到了4.22 MPa、平台应力减小到了4.51 MPa。结论泡沫铝的弹性模量、抗压屈服强度和平台应力均随孔隙率的增加而减小;加热温度低于500℃以下时,泡沫铝材料力学性能变化很小,但屈服强度和弹性模量均小幅度降低;在压缩载荷下,泡沫铝的变形破坏模式呈现出先从试件铝基体较薄弱部分产生孔壁塑性变形、孔洞坍塌,并逐渐出现断裂压缩带,直至泡沫铝孔洞完全坍塌密实。

The work aims to explore the effect of temperature and porosity on the compressive mechanical properties and deformation mechanism of closed-cell aluminum foam materials.The specimens with porosity of 84.3%to 87.3%were heated in the temperature range of 25℃ to 700℃,and the quasi-static compression test was carried out.Under quasi-static compression conditions,the compressive stress-strain curves of closed-cell aluminum foam after heated at different temperature experienced three stages:elastic stage,plastic platform stage and densification stage.When the porosity decreased from 87.3%to 84.3%,the elastic modulus increased by 44.4 MPa,the yield strength increased by 0.39 MPa,and the platform stress increased by 0.94 MPa.At 25℃,aluminum foam with porosity of 84.3%had elastic modulus of 141.4 MPa,yield strength of 4.25 MPa and platform stress of 4.75 MPa.When heating temperature was 500℃,elastic modulus decreased to 128.0 MPa,yield strength decreased to 4.22 MPa and platform stress decreased to 4.51 MPa.The elastic modulus,compressive yield strength and platform stress of aluminum foam decrease with the increase of porosity.When the heating temperature is lower than 500℃,the mechanical properties of aluminum foam materials change little,but the yield strength and elastic modulus decrease slightly.Under the compression load,the deformation and failure mode of aluminum foam shows that the plastic deformation of the pore wall and the collapse of the pore are firstly generated from the weak part of the aluminum matrix of the specimen,and the fracture compression zone gradually appears until the pore of aluminum foam completely collapses.