The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is r...The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.展开更多
To predict the segregation effect in metal injection moulding (MIM) injection, a bi-phasic model based on mixture theory is adopted in simulation. An explicit algorithm is developed and realized by the authors, which ...To predict the segregation effect in metal injection moulding (MIM) injection, a bi-phasic model based on mixture theory is adopted in simulation. An explicit algorithm is developed and realized by the authors, which conducts the simulation to be a cost-effective tool in MIM technology. In case of the bi-phasic simulation, the viscosity behaviours are necessary to be determined for the flows of each phase while only the viscosity of mixture is measurable by tests. It is a crucial problem for application of the bi-phasic simulation of MIM injection. A reasonable method is hence analysed and proposed to determine the viscosity behaviours of each phase. Even though this method may be furthermore modified in the future, it results in the practical simulation of segregation effects with reasonable parameters. The simulation results are compared with the measurements on injected specimens.展开更多
AM （additive manufacturing） of metal parts becomes increasingly important in many industrial fields. However, currently used AM processes like laser melting or electron beam melting are quite complex and expensive. ...AM （additive manufacturing） of metal parts becomes increasingly important in many industrial fields. However, currently used AM processes like laser melting or electron beam melting are quite complex and expensive. The extrusion based AM technology for dense metal components （Composite Extrusion Modelling-CEM）, is characterised by an easy handling and cost efficiency in comparison to powder based processes. The CEM process contains two steps, the additive manufacturing of the green parts and the consecutive sintering. The additive manufacturing of green parts is carried out in a thermally controlled extrusion process. The standard metal injection moulding material with a high proportion of metal and thermoplastic binder is deposited in layers by a heated nozzle. In this way overhangs and bridge structures can be realised. The quality of the green parts that were manufactured with the specifically developed extruder corresponds to typical Fused Deposition Modelling parts. In case the surfaces need to be smooth the green parts can be mechanically post-processed before going through the debinding and sintering process.展开更多
This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products....This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products.The past test results using this method showed a casting yield of 90% to 95%,while conventional methods only show a casting yield of 60% to 70%.Although the press casting method does not require a sprue cup or runner channel casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing part of this casting process.Therefore,we proposed a pressure control method with a mathematical model of molten metal pressure,and with it we achieved experimental confirmation of the successful production of brake drums at different pressing temperatures.Results show that the proposed pressing control method can realize sound,penetration-free casting production.However,the theoretical analysis and design of this pressing process had not previously been studied sufficiently,and therefore this paper presents the theoretical design algorithm for the process as well as its experimental confirmation.展开更多
The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x （x=1, 3, 5, 7, 9） amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials....The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x （x=1, 3, 5, 7, 9） amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials. The amorphous and crystalline states, and thermal parameters, such as the glass transition temperature （Tg）, the initial crystallization temperature （Tx）, the supercooled liquid region （ΔTx=Tx-Tg）, the reduced glass transition temperature T<sup>rg （Tg/Tm, Tm: the onset temperature of melting of the alloy, and Tg/Tl, Tl: the finished temperature of melting of the alloy） were investigated by X-ray diffractometry （XRD） and differential scanning calorimetry （DSC） analysis. Glass forming ability of Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x （x=1,3,5,7,9） bulk metallic glasses has been studied. According to the results, the alloy （x=7） with the highest T<sup>rg （Tg/Tl=0.607, Tg/Tl=0.590） value, has the strongest glass forming ability among these alloys because its composition is near eutectic composition. The wide supercooled liquid region over 72 K indicates the high thermal stability for this alloy system. This bulk metallic glass exhibits quite high strength （Hv 1020）. The success of production of the Fe-based bulk metallic glass with industrial materials is of great significance for the future progress of basic research and practical application.展开更多
We investigated the deformation behaviors of Zr_65Cu_17.5Ni_10Al_7.5 in superplastic forming in silicon mould via numerical modeling and experiments. The data needed for the constitutive formulation were obtained from...We investigated the deformation behaviors of Zr_65Cu_17.5Ni_10Al_7.5 in superplastic forming in silicon mould via numerical modeling and experiments. The data needed for the constitutive formulation were obtained from compressive tests to establish a material library for finite-element simulation using a DEFORM 3D software. A constant speed forming process of a micro gear was modeled where the loading force, feature size and amount of deformation in the micro gear in silicon mould were analyzed in detail for the optimal requirements of micro gear forming and the protection of silicon mould. Guided by the modeling parameters, an amorphous metal micro gear was successfully obtained by our home-made superplastic forming system with the optimized parameters （temperature of 683 K, top speed of 0.003 mm/s until the load force reaching limiting value at 1960 N, and a gradually decelerating process for holding the force to the end）. Our work gives a good example for optimization of superplastic forming and fabrication of BMGs in microparts.展开更多
Fused filament fabrication(FFF)is one of the additive manufacturing processes which has gained more interest because of its simplicity and low-cost.This technology is similar to the conventional metal injection mouldi...Fused filament fabrication(FFF)is one of the additive manufacturing processes which has gained more interest because of its simplicity and low-cost.This technology is similar to the conventional metal injection moulding(MIM)process,consisting of the feedstock preparation of metal powder and polymer binders,followed by layer-by-layer 3D printing(FFF)or injection(MIM)to create green parts and,finally,debinding and sintering.Moreover,both technologies provide near-dense parts.This work presents an in-depth study of the processing method’s influence.The porosity,microstructure,hardness,corrosion,and tribocorrosion behaviour are compared for 17-4 PH SS samples processed from powder by additive manufacturing using FFF and MIM,as well as conventional powder metallurgy(PM)samples.MIM samples exhibited the highest macro and microhardness,while corrosion behaviour was similar for both MIM and FFF samples,but superior in comparison to conventional PM samples.However,the FFF-as fabricated samples displayed a significant improvement in tribocorrosion resistance that could be explained by the higher proportion of delta ferrite and retained austenite in their microstructure.展开更多
基金Project(2007CB613704)supported by the National Basic Research Program of China
文摘The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.
文摘To predict the segregation effect in metal injection moulding (MIM) injection, a bi-phasic model based on mixture theory is adopted in simulation. An explicit algorithm is developed and realized by the authors, which conducts the simulation to be a cost-effective tool in MIM technology. In case of the bi-phasic simulation, the viscosity behaviours are necessary to be determined for the flows of each phase while only the viscosity of mixture is measurable by tests. It is a crucial problem for application of the bi-phasic simulation of MIM injection. A reasonable method is hence analysed and proposed to determine the viscosity behaviours of each phase. Even though this method may be furthermore modified in the future, it results in the practical simulation of segregation effects with reasonable parameters. The simulation results are compared with the measurements on injected specimens.
文摘AM （additive manufacturing） of metal parts becomes increasingly important in many industrial fields. However, currently used AM processes like laser melting or electron beam melting are quite complex and expensive. The extrusion based AM technology for dense metal components （Composite Extrusion Modelling-CEM）, is characterised by an easy handling and cost efficiency in comparison to powder based processes. The CEM process contains two steps, the additive manufacturing of the green parts and the consecutive sintering. The additive manufacturing of green parts is carried out in a thermally controlled extrusion process. The standard metal injection moulding material with a high proportion of metal and thermoplastic binder is deposited in layers by a heated nozzle. In this way overhangs and bridge structures can be realised. The quality of the green parts that were manufactured with the specifically developed extruder corresponds to typical Fused Deposition Modelling parts. In case the surfaces need to be smooth the green parts can be mechanically post-processed before going through the debinding and sintering process.
文摘This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products.The past test results using this method showed a casting yield of 90% to 95%,while conventional methods only show a casting yield of 60% to 70%.Although the press casting method does not require a sprue cup or runner channel casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing part of this casting process.Therefore,we proposed a pressure control method with a mathematical model of molten metal pressure,and with it we achieved experimental confirmation of the successful production of brake drums at different pressing temperatures.Results show that the proposed pressing control method can realize sound,penetration-free casting production.However,the theoretical analysis and design of this pressing process had not previously been studied sufficiently,and therefore this paper presents the theoretical design algorithm for the process as well as its experimental confirmation.
文摘The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x （x=1, 3, 5, 7, 9） amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials. The amorphous and crystalline states, and thermal parameters, such as the glass transition temperature （Tg）, the initial crystallization temperature （Tx）, the supercooled liquid region （ΔTx=Tx-Tg）, the reduced glass transition temperature T<sup>rg （Tg/Tm, Tm: the onset temperature of melting of the alloy, and Tg/Tl, Tl: the finished temperature of melting of the alloy） were investigated by X-ray diffractometry （XRD） and differential scanning calorimetry （DSC） analysis. Glass forming ability of Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x （x=1,3,5,7,9） bulk metallic glasses has been studied. According to the results, the alloy （x=7） with the highest T<sup>rg （Tg/Tl=0.607, Tg/Tl=0.590） value, has the strongest glass forming ability among these alloys because its composition is near eutectic composition. The wide supercooled liquid region over 72 K indicates the high thermal stability for this alloy system. This bulk metallic glass exhibits quite high strength （Hv 1020）. The success of production of the Fe-based bulk metallic glass with industrial materials is of great significance for the future progress of basic research and practical application.
基金Funded by the National Natural Science Foundation of China(Nos.51222508,51175211)
文摘We investigated the deformation behaviors of Zr_65Cu_17.5Ni_10Al_7.5 in superplastic forming in silicon mould via numerical modeling and experiments. The data needed for the constitutive formulation were obtained from compressive tests to establish a material library for finite-element simulation using a DEFORM 3D software. A constant speed forming process of a micro gear was modeled where the loading force, feature size and amount of deformation in the micro gear in silicon mould were analyzed in detail for the optimal requirements of micro gear forming and the protection of silicon mould. Guided by the modeling parameters, an amorphous metal micro gear was successfully obtained by our home-made superplastic forming system with the optimized parameters （temperature of 683 K, top speed of 0.003 mm/s until the load force reaching limiting value at 1960 N, and a gradually decelerating process for holding the force to the end）. Our work gives a good example for optimization of superplastic forming and fabrication of BMGs in microparts.
基金supported by the Ministry of Science and Innovation of Spain under the grant PID2019-109371GB-I00,and by the Junta de Castilla y Leon(VA044G19 y VA2020P20)the funding received from the pre-doctoral grant(2018/12504)with cofinancing from the Government of Castilla-La Mancha and the European Union through the European Social Fund.
文摘Fused filament fabrication(FFF)is one of the additive manufacturing processes which has gained more interest because of its simplicity and low-cost.This technology is similar to the conventional metal injection moulding(MIM)process,consisting of the feedstock preparation of metal powder and polymer binders,followed by layer-by-layer 3D printing(FFF)or injection(MIM)to create green parts and,finally,debinding and sintering.Moreover,both technologies provide near-dense parts.This work presents an in-depth study of the processing method’s influence.The porosity,microstructure,hardness,corrosion,and tribocorrosion behaviour are compared for 17-4 PH SS samples processed from powder by additive manufacturing using FFF and MIM,as well as conventional powder metallurgy(PM)samples.MIM samples exhibited the highest macro and microhardness,while corrosion behaviour was similar for both MIM and FFF samples,but superior in comparison to conventional PM samples.However,the FFF-as fabricated samples displayed a significant improvement in tribocorrosion resistance that could be explained by the higher proportion of delta ferrite and retained austenite in their microstructure.
