Dynamic impact response of nanostructured and hybrid aluminum alloys

铝合金具有密度低、比强度高等优点，是航空航天结构和军用战车防护装甲的首选材料。它们提供了独特的减轻重量的优势，从而提高了飞机的燃油效率，并便于作战车辆的机动性。在这些应用中，铝合金必须具有良好的抗冲击载荷失效能力，无论是飞机的鸟击还是作战车辆中的弹丸。在动态冲击载荷作用下，金属合金发生强烈应变局部化，最终形成绝热剪切带(ASB)。这往往会引发灾难性的失败。合金承受冲击破坏的能力取决于其抗ASB形成的能力。几种高强度铝合金在动态冲击载荷下，由于其对ASB的高敏感性而灾难性地失效。随着现代飞机发动机静音引起的鸟击事件的增加，以及对改进的轻质防护装甲的需求，开发具有更强的抗冲击损伤能力的铝合金是不可避免的。在拟议的研究中，将对选定的铝合金的微观结构进行工程设计，以期使其更耐冲击失效。 晶粒度不均匀是促进金属中ASB产生的主要因素之一。屈服强度较低的较大颗粒优先变形，并作为ASB的起始点。这些带沿着阻力最小的路径传播。制备了具有均匀超细晶(UFG)和纳米混杂结构的改进型铝合金，并对其在动态冲击载荷下的性能进行了研究。含有UFG和/或混杂层状结构的铝合金已经被开发出来，并在静态载荷下进行了表征。然而，它们在动态冲击载荷下对绝热剪切破坏的抵抗力还不是很清楚。可以预见，超细晶的均匀性将降低ASB的形成趋势，而混杂合金中的层状结构将使ASB的路径不连续，并阻碍其扩展。这一点将在本研究中得到验证。开发抗动态冲击破坏能力更强的UFG铝合金是我们的长期目标。其创新之处在于将UFG和分层结构的优点优化结合，实现了高抗冲击性能。这项研究将提供一个新的知识体系，有助于理解晶粒度和层状结构对铝合金中ASB形成的影响。这将有利于加拿大的铝业和运输业。研究成果还将有助于国防部改进作战车辆和军用直升机的防护装甲。培养高素质人才，为国民经济作出贡献。

Aluminum alloys are choice materials for application in aerospace structures and as protective armor in military combat vehicles due to their low density and high specific strength. They offer unique advantages of weight reduction leading to fuel efficiency in aircraft and easy maneuverability in combat vehicles. In these applications, Al alloys must have good failure resistance to impact load, whether from bird strike for aircraft or projectiles in combat vehicles. When exposed to dynamic shock loading, intense strain localization culminating in development of adiabatic shear bands (ASBs) occurs in metallic alloys. This often triggers catastrophic failure. The ability of an alloy to withstand impact failure is determined by its resistance to formation of ASBs. Several high strength aluminum alloys fail catastrophically under dynamic impact loading due to their high susceptibility to formation of ASBs. With increasing incidences of bird strikes due to quieter engines in modern aircraft, and the need for improved lightweight protective armor, development of aluminum alloys with enhanced resistance to impact damage is inevitable. In the proposed study, the microstructures of selected aluminum alloys will be engineered with a view to making them more resistant to impact failure. Grain size inhomogeneity is one of the major factors promoting the initiation of ASBs in metals. The bigger grains with lower yield strength deform preferentially and act as initiation sites for ASBs. These bands propagate along the paths of least resistance. Improved Al alloys with homogeneous ultrafine grained (UFG) and nanostructured hybrid structure will be produced and investigated under dynamic impact loading. Al alloys containing UFG and/or hybrid layered structures have been developed and characterized under static loading. However, their resistance to adiabatic shear failure under dynamic impact loading is not well understood. It is anticipated that the homogeneity of the ultrafine grains will reduce the tendency for ASBs formation while the layered structure in the hybrid alloys will offer discontinuity on the ASBs paths and hinder their propagation. This will be verified in this study. Development of UFG aluminum alloys with enhanced resistance to dynamic impact failure is the long term goal. The novelty lies in an optimum combination of the merits of UFG and layered structures to achieve high impact resistance. The study will provide a new body of knowledge that will help to understand the effects of grain size and layered structures on formation of ASB in Al-alloys. It will be beneficial to Canadian aluminum and transportation industries. The research findings will also benefit the Department of National Defence in the area of protective armor improvement for combat vehicles and military helicopters. Highly Qualified Personnel will be trained to contribute to the national economy.