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。生产每公斤半成品（锭）所需的总能量通常超过600兆焦耳，二氧化碳排放量超过36公斤。在随后的制造阶段，主要是减法制造（SM）过程中，会产生大量的钛合金废料，以切屑的形式产生（可达初始Ti锭的95%），远远大于最终Ti产品。高质量的屑（含较低的O和Fe）通常回收到下游的熔炼阶段，用于铸锭，将其转化为线材需要大约225MJ/kg。或者可以使用固态加工方法（如Confrom、Fastforge和ECAP）直接将其转化为坯料，然而，这些方法对钛合金具有局限性和挑战，例如性能低，刀具磨损严重。通常，他们生产半成品，因此在AM中使用之前，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，使用增材制造（AM）可以显著降低能耗和二氧化碳排放。与SM相比，增材制造大大提高了材料的可用性效率，因为接近或非常接近形状的部件生产只需要很少的精加工步骤。在增材制造中使用金属屑作为原料将对增材制造的经济性产生重大影响，这可能比SM更昂贵，目前限制了其应用以及伴随的材料和排放节约。SM工艺的高买飞比（BTF）需要显著大于线材成本与增材制造半成品成本的比例，才能在经济上合理。使用金属屑，AM的成本将大大降低，这将导致AM更广泛的采用，允许其他重要的收益被利用，包括材料，能源和排放的节省，以及组件的交货时间。因此，我们的研究愿景是利用回收金属屑作为原料的新型金属AM工艺，大大降低高价值近净形组件的整体能源和二氧化碳足迹。并促进整个行业更广泛地利用近净形增材制造技术。为了实现这一愿景，采用了一种新的方法来促进皮肤和核心概念。外皮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，从而形成近净形状组件。芯芯将以固体/液体形式填充经过预处理的高级屑，这些屑可能与原始电线混合以控制氧气水平。现场机械工作将用于控制缺陷和改善材料性能。该研究将包括输入材料特性、工艺开发、材料输出特性、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大有裨益。

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.