Papers by Author: Keith Davey

Abstract: A total weight reduction approach has been key issue for car manufacturers to cope with more and more stringent requirements for fuel economy. This paper describes the twin-roll casting technology of magnesium alloys that contain relatively high weight ratios of aluminum, such as AZ91,AZ101 and AZ111. The magnesium alloy sheets were cast by a horizontal twin roll caster to manufacture relatively high-strength Mg alloys with high aluminum content. The influences of such process parameters as casting temperature and roll speed were ascertained. The microstructures of cast magnesium alloy sheets were observed to investigate the effects of roll-casting conditions on crystal growth in the cast products. It was found that Mg alloys with high aluminum content can be fabricated at a roll speed of 15 m/min with a horizontal-roll caster. The grain size of the manufactured wrought magnesium alloy sheet was about 10 μm due to rapid solidification in the proposed process.

Abstract: This paper describes the twin-roll casting technology of magnesium alloys that contain relatively high weight ratios of aluminum, such as AZ91, AZ101 and AZ111. The magnesium alloy sheets were cast by a horizontal twin roll caster to manufacture relatively high-strength Mg alloys with high aluminum content. The influences of such process parameters as casting temperature and roll speed were ascertained. The microstructures of cast magnesium alloy sheets are observed to investigate the effects of roll-casting conditions on crystal growth in the cast products. It was found that Mg alloys with high aluminum content can be fabricated at a roll speed of 15 m/min with a horizontal-roll caster. The grain size of the manufactured wrought magnesium alloy sheet was about 10 micrometers due to rapid solidification in the proposed process.

Abstract: This paper describes the twin-roll casting technology of magnesium alloys that contain relatively high weight ratios of aluminum, such as AM60, AZ91 and AZ121. The magnesium alloy sheets were cast by a vertical roll caster to manufacture relatively high-strength Mg alloys with high aluminum content. The influences of such process parameters as roll materials, casting temperature, and roll speed were ascertained. A simple method of predicting the convection heat transfer coefficient between casting rolls and molten metal is introduced. The microstructures of cast magnesium alloy sheets are microscopically observed to investigate the effects of roll-casting conditions on crystal growth in the cast products. It was found that Mg alloys with high aluminum content can be fabricated at a roll speed of 90m/min with a vertical-roll caster. The grain size of the manufactured wrought magnesium alloy sheet was about 30 micrometers due to rapid solidification in the proposed process.

Abstract: This paper describes the twin roll casting technology of magnesium alloys that contains relatively high weight ratio of aluminum, such as AM60, AZ91 and AZ121. The cast magnesium alloy sheets were hot-rolled in an elevated temperature to investigate the appropriate hot-rolling conditions for producing high-quality strip using a purpose-built strip-casting mill. The influences of such process parameters as materials of roll, casting temperature, and roll speed are ascertained. A simple method of predicting the convection heat transfer coefficient between casting rolls and molten metal is introduced. The microstructure of the manufactured wrought alloy sheets was observed to investigate the effects of the hot-rolling and heat-treatment conditions on crystal growth in the cast products. It is found that manufacturing thin magnesium alloy sheet was possible at a roll speed of 110m/min by a vertical type roll caster. The grain size of the manufactured wrought magnesium alloys sheet was less than 30 micrometers due to rapid solidification in the proposed process.

Abstract: This paper is concerned with a manufacturing process and technology to facilitate the economical manufacture of high-quality magnesium alloy sheets. Magnesium alloys AZ31, AZ61, AM60 and AZ91 were used to investigate the appropriate anufacturing conditions for use in twin-roll strip casting. Temperatures of the molten materials and roll speeds were varied to find the appropriate manufacturing conditions. The effects of manufacturing conditions on possible forming were clarified in terms of roll speeds and roll gaps between upper and lower rolls. In addition, microscopic observation of the microstructure of the finished casting was performed. It was clarified that a magnesium sheet of 2.5 to 4.5mm thickness could be produced at a speed of 20 m/min by a horizontal copper roll caster. It was also found that the cast magnesium sheet of AZ31, AZ61, AM60 and AZ91 manufactured by roll strip casting could be used for plastic forming if the appropriate magnesium sheets were produced after the roll casting process. By a warm deep drawing test, it also demonstrated that a limiting drawing ratio of 2.4 was possible in the case of AZ91 sheet that was difficult to be manufactured by conventional extrusion process or DC casting and hot-rolling process for magesium alloy sheets with high aluminium contents.

Abstract: Effects of rolling conditions on warm deep drawability of cast magnesium alloy that were hot rolled after roll strip casting were investigated to ascertain the feasibility of twin-roll strip casting process of AZ31B magnesium alloy. Hot rolling and heat treatment conditions were changed to examine which conditions were appropriate for producing AZ31B wrought magnesium alloys after strip casting process. Microscopic observation of the crystals of the manufactured wrought magnesium alloys was performed. It has been found that a limiting drawing ratio of 2.7 was possible in a warm deep drawing test of the cast magnesium alloy sheets after being hot rolled.