The effects of surface roughness were studied on microstructural and mechanical properties of solid-state diffusion bonding between two dissimilar alloys of magnesium AZ91-D and aluminum 6061 by means of hot pressing. Although applied pressure, temperature, and duration of diffusion bonding are known as the most effective parameters, surface roughness can alter the mechanical and microstructural properties remarkably, which is usually neglected. To investigate the effect of surface roughness between 0.06 and 0.15 μm, the width of the diffusion bond in the interfacial transition zone (ITZ) and the presence of intermetallic phases were analyzed. Moreover, microhardness, shear strength, and fracture surfaces were evaluated. The results exhibit that in the applied roughness range, the bond width and the microhardness of the joints improved by increasing the surface roughness of the both metals; however, the shear strength decreased. It may be attributed to more disruption of the oxide films on the metal surfaces in the rougher samples and also increase in the effective interface boundary during the process. Consequently, there would be more chance for aluminum-magnesium contacts, resulting in more diffusion, further formation of brittle intermetallic phases (such as Al₁₂Mg₁₇ and Al₃Mg₂), and therefore more hardness and less shear strength.

中文翻译：

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表面粗糙度对异种AZ91-D镁与AA6061铝合金扩散结合的微观组织和力学性能的影响

通过热压研究了表面粗糙度对AZ91-D镁和6061铝两种异种合金之间固态扩散键合的微观组织和力学性能的影响。尽管施加的压力，温度和扩散键合的持续时间是最有效的参数，但表面粗糙度会显着改变机械和微观结构性能，通常会忽略不计。为了研究表面粗糙度在0.06和0.15μm之间的影响，分析了界面过渡区（ITZ）中扩散键的宽度和金属间相的存在。此外，评价了显微硬度，剪切强度和断裂表面。结果表明，在应用的粗糙度范围内，通过增加两种金属的表面粗糙度，提高了结合宽度和接头的显微硬度。但是，剪切强度降低。这可能归因于在较粗糙的样品中金属表面上的氧化膜更多的破坏，并且在处理过程中有效界面边界也增加了。因此，铝镁接触将有更多的机会，从而导致更多的扩散，进一步形成脆性金属间相（例如Al₁₂ Mg ₁₇和Al ₃ Mg ₂），因此硬度更高，剪切强度更低。