Numerical simulation of a thixocasting process for AISI420 stainless steel air-turbine blade

A new technology,semi-solid casting(thixocasting) method,was used to replace the conventional hot forging process to form AISI420 stainless steel air-turbine blade.The power law cut-off(PLCO) material model in Procast software was used to simulate the thixocasting process.The thixocasting process was simulated.The results show that the reasonable technology parameters for air-turbine blade thixocasting process are obtained:billet temperature 1 483-1 485 °C,piston velocity 12-15 m/s and die temperature is about 400 °C.

Thixocasting combination spanners using stainless steel X39CrMo17

Forging is state-of-the-art for producing hand tools on an industrial scale.Due to high demands on the stiffness and the fracture toughness,high-strength forging steels were used to provide cavity-free components with high mechanical load capacity.Moreover,forging is a cost-effective mass production process but,in spite of all its advantages,it has its limitations,e.g.in the freedom of designs.However,because of the extreme thermal loading(particularly with regard to permanent moulds) and the frequently unavoidable casting defects,hand tools are not cast.By means of thixocasting steel,technical difficulties can be reduced and new options are provided which allow the manufacturing of components with much higher complexity than that using forging.Through near-net shape production,manufacturing steps and costs can be reduced.Furthermore,steels,which are difficult to forge but nonetheless have high potential for specific applications(such as high strength or corrosion resistant steels),can also be processed.In cooperation with industrial partners,X39CrMo17 stainless steel combination spanners with 17 mm width across flats were thixocast.Forming dies were designed and optimized by simulation,the hot forming X38CrMoV5 tool steel as well as the molybdenum alloy TZM were selected as the tool alloys.The dies were treated by a plasma nitriding process and subsequently coated with crystalline Al2O3 protective coatings by plasma-enhanced chemical vapor deposition(PECVD).During the experiments,combination spanners were successfully cast in the semi-solid state.Cast parts were heat-treated to enhance the toughness of components,which was subsequently measured by a standardized torque test.Moreover,a hypothetical approach of a possible,industrial batch process was carried out using the simulation software MAGMAsoft.

Semisolid casting with ultrasonically melt-treated billets of Al-7mass%Si alloys

The demand for high performance cast aluminum alloy components is often disturbed by increasing impurity elements,such as iron accumulated from recycled scraps.It is strongly required that coarse plate-like iron compound of β-Al5FeSi turns into harmless form without the need for applying refining additives or expensive virgin ingots.The microstructural modification of Al-7mass%Si alloy billets with different iron contents was examined by applying ultrasonic vibration during the solidification.Ultrasonically melt-treated billets were thixocast right after induction heating up to the semisolid temperature of 583 oC,the microstructure and tensile properties were evaluated in the thixocast components.Globular primary α-Al is required to fill up a thin cavity in thixocasting,so that the microstructural modification by ultrasonic melt-treatment was firstly confirmed in the billets.With ultrasonic melt-treatment in the temperature range of 630 oC to 605 oC,the primary α-Al transforms itself from dendrite into fine globular in morphology.The coarse plate-like β-Al5FeSi compound becomes markedly finer compared with those in non-treated billets.Semisolid soaking up to 583 oC,does not appreciably affect the size of β-Al5FeSi compounds;however,it affects the solid primary α-Al morphology to be more globular,which is convenient for thixocasting.After thixocasting with preheated billets,eutectic silicon plates are extremely refined due to the rapid solidification arising from low casting temperature.The tensile strength of thixocast samples with different iron contents does not change much even at 2mass% of iron,when thixocast with ultrasonically melt-treated billets.However,thixocast Al-7mass%Si-2mass%Fe alloy with non-treated billets exhibits an inferior strength of 80MPa,compared with 180MPa with ultrasonically melt-treated billets.The elongation is also improved by about a factor of two in thixocastings with ultrasonically melt-treated billets for all iron contents of Al-7mass%Si alloys,for example,the elongation of 11% in thixocast of Al-7mass%Si-0.5mass%Fe alloy with ultrasonically melt-treated billets,5% in that with non-treated billets.

THE INVESTIGATION ON THE RHEOLOGICAL BEHAVIOR OF SEMI-SOLID ALUMINUM ALLOY DURING DIE CASTING

Under the condition of die casting and reheating temperature of 570-580 degC, the rheological behavior of semi-solid aluminum alloy (A356) is pseudoplasticity at the shearrate of 2X10^-1X10^4s^(-1), and also shows dilatancy at the rate over 10~6s^(-1).

Investigation of Properties of Thixoprocessed LM4

Thermomechanical treatment on cast Al-Si-Cu alloy (LM4) was carried out. The aim is to determine effects of degree of cold work, slurry thermal treatment and soaking time on the tensile strength, ductility, hardness and microstructure of the alloy. LM4 was prepared and cast in sand mould into rods of Φ50 mm and 200 mm in length. The prepared rods were then thermally treated at 635°C which fall within the slurry region of the alloy. The heated samples were soaked at this temperature for various times of: 5, 10, 15 and 20 min. A none-treated sample was also kept as control specimen. The thermally treated rods were subjected to various degrees of cold work. 10 %, 15%, 20%, 30% degrees of cold work were used. Hardness, tensile strength and elongation of the samples were determined. The metallographic examination of the samples was also carried out. Results of mechanical property test show sensitivity to degree of cold work, thermal treatment soaking time. The microstructures of the alloy also show significant modifications as a result of thermal treatment.

Development of Deformation-Semisolid-Casting (D-SSC) Process and Applications to Some Aluminum Alloys

Recent advances in the semisolid casting technologies are introduced for aluminum alloys.The advantages of the rheocast and thixocast methods to fabricate alloys with refined spheroidizedα-Al particles are described. The deformation-semisolid-casting （D-SSC） process developed by the author＇s group is presented.The D-SSC process is extremely effective to produce microstructures of refined intermetallic compound particles as well as the spheroidizedα-Al particles in the Al-Si based alloys containing highly concentrated Fe.In the D-SSC processed Al-Si-Cu alloy high elongation of about 20% was achieved even contained concentrated impurity of Fe.The D-SSC process is also useful to produce wrought aluminum alloys with microstructures of refinedα-Al particles.