The mechanisms that govern a previously unexplained hardening effect of a single phase Cu-30wt%Zn -brass after heating have been investigated. After cold-work, the alloy possesses an increased yield strength and hardening rate only when heat treated to temperatures close to 220 °C, and is otherwise softer. Crystallographic texture and microstructure, explored using electron backscatter diffraction (EBSD), describe the deformation heterogeneity including twin development, as a function of the heat treatment conditions. When heated, an increased area fraction of deformation twins is observed, with dimensions reaching a critical size that maximises the resistance to dislocation slip in the parent grains. The effect is shown to dominate over other alloy characteristics including short range order, giving serrated yielding during tensile testing which is mostly eliminated after heating. In-situ X-ray diffraction during tensile testing corroborates these findings; dislocation-related line broadening and lattice strain development between as-worked and heated -brass is directly related to the interaction between the dislocations and the population of deformation twins. The experiments unambiguously disprove that other thermally-induced microstructure features contribute to thermal hardening. Specifically, the presence of recrystallised grains or second phases do not play a role. As these heat treatments match annealing conditions subjected to -brass during deformation-related manufacturing processes, the results here are considered critical to understand, predict and exploit, where appropriate, any beneficial process-induced structural behaviour.

中文翻译：

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[式略]黄铜热处理诱导硬化的微观力学研究


研究了控制单相 Cu-30wt%Zn 黄铜加热后先前无法解释的硬化效应的机制。冷加工后，只有在热处理到接近 220 °C 的温度时，该合金才会具有更高的屈服强度和硬化率，否则会变得更软。使用电子背散射衍射 (EBSD) 探索的晶体织构和微观结构描述了变形不均匀性，包括孪晶发育，作为热处理条件的函数。加热时，观察到形变孪晶面积分数增加，尺寸达到临界尺寸，使母体晶粒中对位错滑移的阻力最大化。该效应显示出优于其他合金特性，包括短程有序，在拉伸测试期间产生锯齿状屈服，而加热后大部分被消除。拉伸试验期间的原位 X 射线衍射证实了这些发现；加工态黄铜和加热黄铜之间与位错相关的线展宽和晶格应变发展与位错和变形孪晶群体之间的相互作用直接相关。这些实验明确地证明了其他热致微观结构特征有助于热硬化。具体来说，再结晶晶粒或第二相的存在不起作用。由于这些热处理与变形相关制造过程中黄铜的退火条件相匹配，因此这里的结果被认为对于理解、预测和利用（在适当情况下）任何有益的过程引起的结构行为至关重要。