Gradient twinning microstructure generated by laser shock peening in an AZ31B magnesium alloy
Gradient twinning microstructure generated by laser shock peening in an AZ31B magnesium alloy
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DOI：
10.1016/j.apsusc.2018.06.176
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发表时间：
2018-11
影响因子：
6.7
通讯作者：
B. Mao;Y. Liao;Bin Li
中科院分区：
文献类型：
--
作者：
B. Mao;Y. Liao;Bin Li
镁合金是轻质结构金属，在各种工程应用中具有广阔的前景。然而，镁合金的使用往往因其较差的机械性能而受到限制。最近的研究表明，一种新型的基于激光的表面处理技术——激光冲击喷丸（LSP），有望通过提高镁合金的表面强度、生物相容性、抗疲劳性和抗腐蚀性能来改善镁合金的工程性能。尽管有这些实验努力，但很少有人关注LSP过程中表面微观结构的演变，特别是高密度变形孪晶的形成。密排六方（HCP）晶体结构中的形变孪生对于提高镁合金的机械性能起着重要作用。本研究旨在建立 LSP 加工镁合金的工艺-显微组织关系。重点是理解变形孪生机制。 LSP 实验是在轧制的 AZ31B 镁合金上进行的。对激光加工前后的微观结构进行了表征。研究了激光强度对孪晶体积分数的影响。测量与孪晶密度相关的表面硬度。讨论了梯度孪晶微观结构形成的机制和孪晶诱导硬化效应。讨论了 Mg 样品中晶粒取向对 LSP 的各向异性响应以及由此产生的微观结构和硬度的改善。
Mg alloys are lightweight structural metals that are promising for a variety of engineering applications. However, use of Mg alloys is often restricted by their poor mechanical properties. Recent studies indicate that a novel laser-based surface processing technology, laser shock peening (LSP), is promising to improve the engineering performance of Mg alloys by enhancing their surface strength, biocompatibility, fatigue resistance, and anti-corrosion ability. Despite these experimental efforts, little attention has been paid to study the surface microstructure evolution in the LSP process, particularly the formation of high density deformation twins. Deformation twinning in hexagonal closed-packed (HCP) crystal structure plays a fundamental role in enhancing mechanical performance of Mg alloys. This research is to establish the process-microstructure relationship of Mg alloys as processed by LSP. A focus is placed on understanding the deformation twinning mechanism. LSP experiments are conducted on a rolled AZ31B Mg alloy. The microstructures before and after laser processing are characterized. The effect of laser intensity on the twin volume fraction is investigated. The surface hardness as associated with the twin density is measured. The mechanism responsible for the formation of gradient twinning microstructure and the twinning-induced hardening effect are discussed. The anisotropic response to LSP in terms of grain orientation and the resultant microstructure and hardness improvement in the Mg samples are discussed.