Semi-solid rheocasting of grain refined aluminum alloy 7075
Near-net shape rheocasting with the Council for Scientific and Industrial Research Rheo casting system(CSIR-RCS) and a high pressure die casting machine was successfully performed on Al-5Ti-1B grain refined aluminum alloy 7075. Grain refinement levels used were 0.03％ Ti, 0.13％ Ti and 0.29％ Ti (mass fraction). Tensile tests reveal that the ultimate tensile strengths, at all levels of grain refinement, are at least 97％ of the specified minimum. Elongation at fracture increases with the increase of level of grain refinement although a maximum elongation is only 76％ of the required minimum elongation in the ease of 0.29％ Ti. Incipient melting, during solution treatment, of the low melting point multinary euteetic causes porosity in the material and accounts for poor elongation results. 0.03％ Ti has a coarse eutectic structure forming larger pores while 0.29％ Ti has a fine structure forming fine pores in the multinary euteetie. The 0.2％ offset yield strengths of all the grain refinement levels are at least equal to or above the specified minimum and a decrease is observed with the increase of grain refinement level. There is a clear reduction in grain size from 0.03％ Ti to 0.29％ Ti in the as-cast condition. An underlying grain structure develops in the T6 condition material which has an inverse size to the as-east structure;coarse grained as-cast material results in fine grained T6 condition material after solution heat treatment. The decrease in the offset yield strength as grain refinement increases correlates very strongly with the T6 grain sizes according to a Hall-Petch type relationship.
CSIR-RCS 7075 Al-5Ti-1B high pressure die casting F condition T6 condition incipient melting
U. A. CURLE G GOVENDER
Materials Science and Manufacturing, Council for Scientific and Industrial Research, Pretoria, South Africa
国际会议
北京
英文
832-836
2010-09-16（万方平台首次上网日期，不代表论文的发表时间）