Laser Beam - Splitting and Materials Processing

与材料激光加工相关的强烈热源通常会影响被加工零件的微观结构。例如，在激光焊接中，由此产生的高冷却速度往往会在高淬透性材料中产生脆性组织。这类材料通常在焊接前预热，也可能在焊接后进行热处理。传统的预热和焊后热处理通常要么过于昂贵，要么不切实际。这样的热处理会降低生产率，并可能影响材料的其他部分。为了消除这些问题，研究人员将研究分束激光焊接的概念，即激光光束将被一分为二，产生双热源。主要的次要电源将预热材料，而主要电源将用于实际焊接。这种由引导源预热的方式，将一步到位地实现常规预热方式下较低的冷却速度。这种通过分束激光对微结构的控制可以扩展到其他材料加工应用，例如表面热处理。这项工作将包括对问题的热分析，然后(在很大程度上与之并行)广泛的实验计划，以验证分析，并阐明分束激光材料加工概念的潜在好处。实验任务将构成研究项目的主要部分。

The intense heat sources associated with laser processing of materials often affect the microstructure of the part being processed. For example, in laser beam welding, the resulting high cooling rates tend to produce brittle microstructures in high hardenability materials. Such materials are normally pre-heated before welding and may also be subjected to post-weld heat treatment. Conventional pre-heating and post-weld heat treatment are often either too expensive or impractical to use. Such heat treatments reduce productivity and may affect other parts of the material. To eliminate these problems, the researcher's will investigate the split-beam laser welding concept, where the laser beam will be split into two, resulting in a dual heat source. The leading minor source will pre-heat the material while the major source will be used for the actual welding. This pre-heat by the leading source will achieve the lower cooling rate induced by conventional pre-heating in a single step. Such control of microstructure by splitting of the laser beam can be extended to other materials processing applications such as surface heat treatment. The work will include a thermal analysis of the problem, followed by (and to a large extent parallel with) an extensive experimental program both to verify the analyses, and to elucidate the potential benefits of the split-beam laser materials processing concept. The experimental task will constitute the bulk of the research project.