Effect of low-frequency electromagnetic field on the as-cast microstructure of a new super high strength aluminum alloy by horizontal continuous casting
The super high strength aluminum alloy ingots with 100 mm in diameter were cast by the process of low-frequency electromagnetic horizontal continuous casting (LFEHC) and the effect of electromagnet ic field on the as-cast microstructure was studied. Results show that microstructure of the sample prepared by the LFEHC process was greatly refined. Microstructures at the border and the center of the ingots were fine, uniform and rosette-shaped. Electromagnetic frequency plays a key role in microstructure refining. Fine and uniform microstructures can be obtained with optimal electromagnetic frequency. In this experiment, under a frequency of 30 Hz the microstructure was the finest and the most uniform.
Intracrytalline element solubility and mechanical property of a new super-high strength and toughness Al alloy cast under low frequency electromagnetic field
A new superhigh strength and toughness Al alloy (10Zn25Mg25Cu015ZrbalanceAl) was semicontinuously cast on the basis of CREM (casting, refining, electromagnetic), by lowering the electromagnetic frequency to 15～35Hz The differences of microstructure, intracrytalline element solubility and mechanical properties between DC and low frequency electromagnetic casting were investigated The effect of electromagnetic frequency and number of ampere turns on intracrytalline element solubility and mechanical properties were focused on The results show that low frequency electromagnetic cast microstructures of 10Zn25Mg25Cu015ZrbalanceAl alloy are well refined, and intracrytalline element (Zn,Mg and Cu) solubility and mechanical properties are greatly increased It also shows that when the optimum frequency is 15～25Hz and number of ampere turns is 12800～16000A, intracrytalline element (Zn,Mg and Cu) solubility are higher, and mechanical properties are the best The billets were extruded into 12mm bars and their tensile ultimate strength are 780MPa and the elongation are greater than 8% after thermal treatment
Hydrogen embrittlement and trapping in Al6%Zn-3%Mg
Abstract The embrittlement of Al-6wt.%Zn-3wt.%Mg alloy exposed to water vapour at elevated temperatures has been investigated. The results indicate that the loss in ductility of sheet tensile specimens is the result of intergranular hydrogen embrittlement. Trapping of hydrogen in bubbles nucleated at grain boundary precipitate particles inhibits the embrittlement. A critical particle size of approximately 200 A is required for bubble nucleation. Resistance to embrittlement can be obtained by adjustment of the heat treatment to produce suitable grain boundary particle dispersions.