Sustainable Additive Manufacturing

制造高性能和高价值的材料，如钛合金，通常是能源密集型和昂贵的。每生产一公斤钛半成品（钛锭）所需的总能量通常超过600兆焦耳，碳足迹超过36公斤。在随后的制造阶段，主要是减材制造（SM）过程中，会产生大量的钛合金废料（可高达初始钛锭的95%），其数量远远大于最终钛产品的数量。高品位的切屑（含O和Fe较低）通常在下游回收到铸锭的熔化阶段，这需要约225 MJ/kg将其转化为线材。也可以采用固态加工方法直接将其转化为坯料，例如Confrom，Fastforge和ECAP，但是它们对于钛合金具有限制和挑战，例如低性能和严重的工具磨损。通常，它们会产生半成品，因此在用于AM之前需要进一步加工成线材或粉末，这通常包括另一个熔化步骤。研究表明，通过使用增材制造（AM）可以显着减少能源消耗和二氧化碳排放。与SM相比，AM大大提高了材料的可用性效率，这是由于几乎或非常接近形状的部件生产，只需要很小的精加工步骤。在AM中使用切屑作为原料将对AM的经济性产生重大影响，AM可能比SM更昂贵，目前限制了其应用以及伴随的材料和排放节省。SM工艺的高Buy-to- Fly（BTF）比率需要显著大于AM的线材成本与半成品成本的比率，才能在经济上合理。使用切屑，AM的成本将大大降低，这将导致AM的更广泛采用，允许其他重要的收益被利用，包括材料，能源和排放节省，以及组件交货时间。因此，我们的研究愿景是利用回收的切屑作为原料的新型金属AM工艺，能够大大降低高价值近净形组件的整体能源和CO2足迹，为了实现这一愿景，提出了一种新的方法，该方法促进了皮肤和核心概念。外层将使用原始材料沉积，具有高分辨率，提供精确的几何定义和光滑的外表面，从而形成近净形部件。芯部将填充有预处理的高等级切屑，以固体/液体形式，其可以与原始线材混合以控制氧气水平。原位机械加工将用于控制缺陷和改善材料性能。该研究将包括输入切屑材料表征，工艺开发，材料输出表征，工艺建模，SAM概念验证以及环境和经济评估等活动。SAM将为英国的“净零”战略做出贡献。它还将提供更广泛的学术影响，因为开发的许多技术和工具将与其他AM和相关技术直接相关并带来巨大好处。

It is usually energy intensive and expensive to manufacture high performance and high-value materials, such as titanium alloys. The total energy required is typically more than 600 MJ to get each kg to get the semi-finished Ti products (ingots), with more than 36 kg CO2 carbon footprint. During the subsequent manufacturing stage, mainly subtractive manufacturing (SM) process, a large amount of Ti alloy scrap is generated in the form of swarf and chips (can be up to 95% of the initial Ti ingot) which is far greater than that of the final Ti products. High-grade swarf (with lower O and Fe) is usually recycled downstream to the melting stage for ingots which requires about 225MJ/kg to convert it to wire. Or it can be directly converted into billets using solid state processing methods, such as Confrom, Fastforge, and ECAP, however, they have limitations and challenges for titanium alloy, such as low properties, and sever tool wear. Often, they produce semi-finished products, so further processing into wire or powder is required before they can be used in AM, which usually includes another melting step. Studies have shown that a remarkable reduction in energy consumption and CO2 emission can be achieved by using additive manufacturing (AM). Compared to SM, AM improves the material usability efficiency greatly due to the near or very near shape component production with just minor finishing steps required. Using swarf as feedstock in AM will have a major impact on the economics of AM, which can be more expensive than SM, currently restricting its application and concomitant material and emissions savings. A high Buy-to- Fly (BTF) ratio for SM process needs to be significantly greater than the ratio of the wire cost to the semi-finished product cost for AM to be economically justifiable. Using swarf, the cost of AM will be drastically lowered, which will lead to much more widespread adoption of AM, allowing other important gains to be exploited, including material, energy, and emission savings, and component lead timesTherefore, our research vision is Novel metal AM processes that utilise recycled swarf as feedstock, enabling a greatly reduced overall energy and CO2 footprint for high-value near-net-shaped components, and facilitating much wider exploitation of near-net-shape AM technologies throughout industry.To deliver this vision, a new method which facilitate a skin and core concept. The outer skin will be deposited using virgin material, with high resolution providing accurate geometric definition and a smooth outer surface, leading to a near-net shape component. The core will be in-filled with pre-processed high-grade swarf, in a solid/ liquid form, which may be mixed with virgin wire to control oxygen levels. In-situ mechanical work will be applied to control defects and improve the material properties. The research will comprise activities on input swarf material characterisation, process development, material output characterisation, process modelling, SAM concept validation, and environmental and economic assessment. SAM will contribute to the 'net-zero' strategy of the UK. It will also provide wider academic impact as many techniques and tools developed will be of direct relevance and great benefit to other AM and related technologies.