Dynamic impact response of nanostructured and hybrid aluminum alloys

铝合金具有密度低、比强度高的特点，是航空航天结构和军用作战车辆防护装甲的首选材料。它们提供了独特的优势，减轻了重量，从而提高了飞机的燃油效率，并在战斗车辆中易于操作。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战斗车辆的弹丸。当暴露在动态冲击载荷下时，金属合金中会发生强烈的应变局部化，最终导致绝热剪切带（asb）的发展。这通常会引发灾难性的失败。合金抗冲击失效的能力是由其抗asb形成的能力决定的。由于高强度铝合金极易形成asb，因此在动态冲击载荷下会发生灾难性失效。由于现代飞机发动机的噪音越来越小，鸟撞事件越来越多，而且需要改进轻型防护装甲，因此开发具有增强抗冲击损伤能力的铝合金是不可避免的。在拟议的研究中，将对选定铝合金的微观结构进行设计，以使其更能抵抗冲击失效。******晶粒尺寸的不均匀性是促进金属中ASBs发生的主要因素之一。屈服强度较低的大晶粒优先变形，是asb的起始点。这些带沿着阻力最小的路径传播。在动态冲击载荷作用下，将制备和研究具有均匀超细晶和纳米杂化结构的改进铝合金。含UFG和/或杂化层状结构的铝合金在静载荷下得到了发展和表征。然而，它们在动态冲击载荷下的抗绝热剪切破坏能力尚不清楚。预计超细晶粒的均匀性将减少asb形成的趋势，而混杂合金中的层状组织将使asb路径不连续并阻碍其扩展。这将在本研究中得到验证。开发具有增强动态冲击失效抗力的UFG铝合金是长期目标。新颖之处在于UFG和层状结构的优点的最佳结合，以实现高抗冲击性。该研究将提供一个新的知识体系，将有助于理解晶粒尺寸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。研究结果也将有利于国防部在战斗车辆和军用直升机防护装甲改进领域。将培养高素质人才，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.