Cr对ECO-7175铝合金热压过程中流变行为和加工图的影响

Effect of Cr elimination on flow behavior and processing map of newly developed ECO-7175 aluminum alloy during hot compression

研究Cr元素对新开发的ECO-7175合金热变形行为的影响。采用Gleeble热模拟机对含Cr和不含Cr的ECO-7175样品进行热压(温度为350~500℃、应变速率为0.001~1 s^(−1)),研究合金的本构方程、加工图和显微组织演变。对变形激活能的分析表明,含Cr合金中速率控制变形机制由Al的自扩散(或Al中Mg的扩散)逐渐转变为Al中Cr的扩散,且Zener−Hollomon参数减小。对含Cr合金的加工图的分析表明,动态再结晶(DRX)区局限于高温和低应变速率下的变形,且随着应变的增加而扩大。另一方面,发现Al的自扩散(或Al中Mg的扩散)是无铬合金在所有加工条件下热变形过程中唯一的速率控制机制,其DRX区与塑性应变无关。

ECO-Al alloys are introduced as a game-changer for the aluminum industry and it is of utmost importance to determine the role of alloying elements in their processing characteristics.In this study,the effects of Cr on the hot deformation behavior of newly-developed ECO-7175 alloy were investigated.ECO-7175 samples with and without Cr were hot-compressed using a Gleeble simulator(temperature range of 350−500℃ and strain rates of 0.001−1 s^(−1)).The results were used to study the constitutive equations,the processing maps,and the microstructural evolution of the alloys.In Cr-containing alloy,the analysis of the deformation activation energy reveals that the rate-controlling mechanisms of the deformation change gradually from self-diffusion of Al(or diffusion of Mg in Al)to diffusion of Cr in Al by decreasing the Zener−Hollomon parameter.The analysis of the processing maps of Cr-containing alloy shows that the dynamic recrystallization(DRX)zone is limited to the deformation at high temperatures and low strain rates and expands with increasing applied strain.On the other hand,it is found that the self-diffusion of Al(or Mg in Al)is the only rate-controlling mechanism during hot deformation of Cr-free alloy in all processing conditions and its DRX zone is independent of the plastic strain.