Gas Release Behavior of Cu-TiH 2 Composite Powder and Its Application as a Blowing Agent to Fabricate Aluminum Foams wit
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NTRODUCTION
ALUMINUM foams possess many remarkable properties, which allow them to be used for numerous applications.[1–3] Among various fabrication routes,[4–8] one promising way for commercial production is the melt foaming method: foaming by adding a blowing agent into the thickened aluminum melt.[9,10] TiH2 powder is the most widely used blowing agent.[2] So far, studies are mainly focused on preparing foams with high porosity (‡ 80 pct) and large pore size (3 to 6 mm).[11–14] Compared to traditional pore structure with high porosity (‡ 80 pct) and large pore size (‡ 3 mm), aluminum foams with low porosity (60 to 70 pct) and small pore size (£ 2 mm) possess higher compressive property and formability. Zou et al.[15] proposed a fabrication method of aluminum foams with low porosity for the first time. Their results show that the compressive yield strength is 3 to 7 times greater than that of traditional polygonal pore aluminum foams with
YING CHENG, ZHIYONG LIU, XU ZHOU, and NINGZHEN WANG are with the School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P.R. China. YANXIANG LI and XIANG CHEN are with the School of Materials Science and Engineering, Tsinghua University, and also with the Key Laboratory for Advanced Materials Processing Technology, MOE, Beijing, P.R. China. Contact email: [email protected] Manuscript submitted July 31, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
high porosity. Also, the energy absorption capacity increases by 3 times. Babscan et al.[16,17] found that when the pores exist in a spherical shape and their size is around 1 mm, the foams can be further processed by thermal processing methods, such as casting, rolling, and welding. The preceding experimental results demonstrate that aluminum foams with low porosity (60 to 70 pct) and small pore size (£ 2 mm) can be recognized as a new type of porous metal materials. On the one hand, it possesses much higher strength and energy absorption capacity. On the other hand, it can be further processed into various complex shapes. These excellent features can obviously extend the application fields of aluminum foams. The existing methods to obtain this new type of aluminum foams all require a short foaming time and rapid solidification.[15,18,19] However, the thermal conductivity of aluminum foams is poor.[20] Therefore, it is difficult to realize simultaneous rapid solidification of the entire foam, especially when the foam size is large. If the solidification stage is started far before the foaming stage is ended, a uniform pore structure is hard to be ensured.[9] In order to overcome this drawback, we proposed a new type of blowing agent: Cu-TiH2 composite powder. It was prepared by ball milling preoxidized TiH2 powder with Cu powder. In our previous study,[21] aluminum foams with low porosity and small pore size were successfully prepared by using such composite powder as the blowing agent. Also, rapid solidification is not needed. Thus, the entire
fabrication process and the uniformity of final pore struct
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