Shock effects on the upper limit of the collision weld process window

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process windows.Thus,the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld interface.Current formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld material.However,collision welding fundamentally depends on the impacts that generate shockwaves in weld members,which can dominate the stress propagation velocities in thin weld sections.Therefore,this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D Rankine-Hugoniot relations.The shock upper limit is validated against the experimental and simulation data in the collision welding literature,and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.

基于中间过渡层的5A06/0Cr18Ni10Ti气化冲击焊接工艺研究

利用气化冲击焊接技术,制备了力学性能良好基于中间层的5A06铝合金与0Cr18Ni10Ti不锈钢气化冲击焊接接头,中间层3003铝合金与飞板5A06铝合金和靶板0Cr18Ni10Ti界面焊接良好,接头结合区域呈圆环状。通过信号采集系统分析了铝箔气化时间和电流随能量输入的变化,采用OM和SEM分析了接头界面的微观形貌和元素分布。研究了能量输入对铝箔气化的时刻和接头力学性能的影响。结果表明,随着能量输入的增加,铝箔气化所需时间减小,最终碰撞速率增大,从而使焊接区域直径增大;接头的抗拉力和抗剪力随能量输入的增大而增大。当能量输入为9 kJ时,接头的最大抗拉力为44.0 k N,抗剪力为2.1 kN;5A06/3003界面呈中间对称波状结合,3003/0Cr18Ni10Ti界面以金属间化合物连接,结合区域错位分布。

Multi-scale characterization and simulation of impact welding between immiscible Mg/steel alloys

Vaporizing foil actuator spot welding method is used in this paper to join magnesium alloy AZ31 and uncoated high-strength steel DP590,which are typically considered as un-weldable due to their high physical property disparities,low mutual solubility,and the lack of any intermetallic phases.Characterization results from scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)of the weld interface indicate that the impact creates an Mg nanocrystalline interlayer with abundant Fe particles.The interlayer exhibits intact bonding with both DP590 and AZ31 substrates.To investigate the fundamental bond formation mechanisms at the interface,a finite element(FE)-based process simulation is first performed to calculate the local temperature and deformation at the interface under the given macroscopic experimental condition.Taking the FE results at the interface as inputs,molecular dynamics(MD)simulations are conducted to study the interlayer formation at the Mg/Fe interface during the impact and cooling.The results found a high velocity shearing-induced mechanical mixing mechanism that mixes Mg/Fe atoms at the interface and creates the interlayer,leading to the metallurgical bond between Mg/steel alloys.

Improved properties and thermal stability of a titanium-stainless steel solid-state weld with a niobium interlayer

Stainless steel(SS)and titanium alloys can be welded in the solid-state by high speed oblique impact.Here,the effect of a niobium(Nb)interlayer on weld strength and thermal stability is evaluated.Both Ti/SS and Ti/Nb/SS welds were subjected to thermal exposure ranging from 300℃ to 950℃ for 1.5 h.Thermal exposure monotonically decreases the strength and toughness of the Ti/SS pair with a dramatic falloff in strength and change in failure mode from partial pullout failure to full interfacial fracture at 600℃.With the interlayer,toughness was increased versus baseline up to 700℃ thermal exposure and then intermetallic formation again caused falloff in properties.Guidelines for the production,properties and applications of these classes of welds are provided.