The development of effective grain refiner for the production of high performance light metal castings

铝-硅（Al-Si）合金是重要的合金，因为它们重量轻（2.7g/cc）、易于回收、耐腐蚀、耐用且环境友好。与钢（7.8 g/cc）相比，它们具有更高的强度重量比。90%的铝型材铸件是基于这些铝硅合金，目前，每年约有500万吨用于汽车工业。2006年生产的汽车平均含铝110-145公斤，而钢约为1000公斤。生命周期分析表明，通过用铝零件替代钢，重量减少100公斤，将在汽车的寿命（200，000公里）内节省900升汽油，并节省2，000公斤二氧化碳（10克/公里）。对于轻金属工业来说，在增加这些轻质Al-Si合金在运输部门中替代钢的进一步使用方面的大问题是缺乏与大晶粒结构、缺陷和大金属间化合物颗粒相关的延展性和屈服强度。由于Al-Si合金难以晶粒细化，目前由于过多的铸造缺陷和不足的机械性能而限制了其广泛应用。这些合金中较高的Si含量导致大晶粒，这使得铸造困难，从而导致非常高的废品率，对于高价值关键部件高达60%。由于Si和Ti之间的反应，用于非铸造（锻造）Al合金的Ti基晶粒细化剂在铸造Al-Si合金中效果较差。Brunel发明了一种有效的晶粒细化剂，可以彻底改变这些Al-Si铸造合金的铸造工艺，显著减少铸造缺陷并产生上级机械性能，尽管（故意）有限的宣传，但已经在材料供应链中产生了巨大的市场兴趣。Brunel晶粒细化剂（BGR）改善了各种铝合金的铸造性;消除了铸件中常见的热裂问题;提高了急需的抗拉强度和延展性;提高了整个部件的机械性能均匀性;实现了薄壁铸造结构;并允许高杂质含量（现在可以制造具有上级性能的铝废料）。此外，它还可以使用砂型铸造大型和复杂形状的结构，并降低高价值部件制造过程中的高废品率（高达60%）。Brunel晶粒细化剂的独特卖点在于，它对大型铸件非常有效，并且易于在行业中使用。目前还没有有效的铝硅合金铸件晶粒细化剂，以前很难生产出无缺陷的高性能大体积铸件，现在可以很容易地进行加工。它为各种铸造技术带来了好处，应该能够生产出具有上级性能的铸件，使铝在汽车行业中取代越来越多的钢部件。这将使英国处于冶金技术发展的前沿。由于重量轻以及随之而来的能源消耗和二氧化碳排放量的减少，预计将产生非常可观的环境效益。

Aluminium-Silicon (Al-Si) alloys are important alloys as they are lightweight (2.7 g/cc), easily recycled, corrosion resistant, durable and environmentally friendly. In comparison with steel (7.8 g/cc), they have higher strength to weight ratio. 90% of aluminium shape castings are based on these Al-Si alloys and currently, ~ 5 million tonnes per annum are being used in automotive industry. The average car manufactured in 2006 contained between 110-145 kg of Aluminium, compared to ~1000 Kg of Steel. Life cycle analysis suggest that, a 100 kg weight reduction through substituting Steel with Aluminium parts would result in a saving of 900 litres of petrol during the car's life span (200,000 km) and 2,000Kg of CO2 savings (10 g/km). The big problem for the light metal industry in increasing the further use of these lightweight Al-Si alloys with respect to replacing steel in the transport sector is the lack of ductility and yield strength associated with the large grain structure, defects and large intermetallic particles. Since Al-Si alloys are difficult to grain refine, widespread adoption is currently constrained due to excessive casting defects and inadequate mechanical properties. Higher Si levels in these alloys results in large grains, which make casting difficult, thus resulting in very high rejection rates, up to 60% for high value critical components. Ti based grain refiners used for non-cast (wrought) Al alloys are less effective in cast Al-Si alloys due to reaction between Si and Ti. Brunel has invented an effective grain refiner that can revolutionize the foundry casting process for these Al-Si casting alloys, significantly reducing the casting defects and producing superior mechanical properties that, despite (deliberately) limited publicity, is already generating significant market interest within the materials supply chain. The Brunel grain refiner (BGR) improves castability of a wide range of aluminium alloys; eliminates hot-tearing, a common problem in castings; it improves much needed tensile strength and ductility; improves homogeneity in mechanical properties across the component; it enables thin-wall cast structures; and it tolerates high impurity levels (aluminium scrap can now be manufactured with superior properties). Additionally, it is expected to enable the casting of large and complex shaped structures using sand moulds and reduce the high (up to 60%) rejection rate during manufacture of high value components.The unique selling points of the Brunel Grain refiner are that it is highly effective for bulk castings and easily employable by the industry. Currently there exists no effective grain refiner for Al-Si castings and previously difficult to produce high performance bulk castings without defects can now be easily processed.Delivering benefits to a wide range of casting techniques, it should enable the production of castings with superior properties, allowing aluminium to replace a growing proportion of steel parts in the automotive sector. This will put the UK in the forefront of metallurgical technological developments. Very substantial environmental benefits are foreseen due to light-weighting and concomitant reductions in energy consumed and CO2 emitted.