纯铝、铁与钛薄板各向异性比较

Comparation of anisotropy of pure aluminum,iron and titanium sheets

为了明晰晶体结构对金属薄板塑性各向异性(r值)的影响,以3种典型晶体结构的高纯金属材料1A99纯铝、YT01纯铁和TA1纯钛为研究对象,采用数字图像相关技术并结合三阶多项式拟合法探究其r值演化规律。结果表明,在各向异性方面,纯铝与取样方向相关,这是取样方向与主滑移系之间的关系所致;而纯钛为各向同性,这仅与密排六方结构有关;而纯铁介于两者之间没有明显规律,这不仅与取样方向有关,还与BCC结构有关。在r值方面,纯铝不同方向的r值均小于1,而纯铁的r值稍大于1,纯钛的r值均大于1.68。说明在抗减薄能力上纯钛>纯铁>纯铝,这与晶体结构相一致。同时在取样90°时三者均有较优的抗减薄能力,这与取样方向偏离主滑移系最远有关。最后,在r值演化方面,纯铝在3个方向上差异巨大,而纯铁均先增大后减小,纯钛除取样0°几乎不变外均先减小后增大,这些复杂的现象可能与择优取向组织的体积分数和织构演化有关。

To clarify the influence of crystal structure on the plastic anisotropy(r-value)of sheet metal,three high-purity metallic materials 1A99 pure aluminium,YT01 pure iron and TA1 pure titanium with typical crystal structures were studied to investigate the r-value evolution laws based on digital image correlation techniques and third-order polynomial fitting method.The results show that in terms of anisotropy,pure aluminium is correlated with the sampling direction,which is due to the relationship between the sampling direction and the main slip system;pure titanium is isotropic,which is only related to the densely-arranged hexagonal structure;pure iron has no obvious regularity in between,which is not only related to the sampling direction,but also related to the BCC structure.In terms of r-value,the r-value of pure aluminium in different directions is less than 1,while the r-value of pure iron is slightly greater than 1,and the r-value of pure titanium is greater than 1.68,which indicates that pure titanium>pure iron>pure aluminium in terms of the resistance to thinning,which is consistent with the crystal structure.At the same time,all three have better thinning resistance when sampling at 90°,which is related to the fact that the sampling direction is the furthest away from the main slip system.Finally,in terms of r-value evolution,pure aluminium varies greatly in three directions,while pure iron increases firstly and then decreases,and pure titanium decreases firstly and then increases except for sampling at 0°where it is almost unchanged,and these complex phenomena may be related to the evolution of volume fractions and texture in the preferentially oriented tissues.