Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using sc...Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.展开更多
Upon approaching 850℃,the GH4151 alloy exhibits diminished high-temperature strength,primarily attributed to the disruption of γ′phase coherence at elevated temperatures,which reduces its strengthening contribution...Upon approaching 850℃,the GH4151 alloy exhibits diminished high-temperature strength,primarily attributed to the disruption of γ′phase coherence at elevated temperatures,which reduces its strengthening contribution.Tantalum(Ta)additions enhance the stability of the γ′phase but introduce processing challenges,including pronounced solidification segregation,the formation of secondary phases,and increased susceptibility to cracking during processing.The influence of Ta content on elemental segregation,solidification microstructure,phase precipitation kinetics,and hot deformation behaviour in GH4151 was systematically investigated.Processing windows derived from the dynamic materials model(DMM)and microstructural evolution under varying thermomechanical conditions are further examined.Key findings reveal the severe Ta segregation(segregation coefficient K≈1.608);Ta promotes γ/γ′eutectic and η phase formation,increasing γ′phase volume fraction from 54% to approximately 63%;and increased Ta content elevates flow stress and progressively narrows the DMM-defined processing window;optimized thermomechanical processing parameters(elevated temperatures and strain rates)enhance recrystallization kinetics and hot workability,thereby mitigating cracking propensity.展开更多
The dependences of the microstructure and hardness of the binary Cr Ta alloys [Cr 9.0, 9.2, 9.4, 9.6, 9.8, and 13.0 Ta] (mole fraction, %) were investigated. When Ta content of the alloy is less than 9.4%, there are p...The dependences of the microstructure and hardness of the binary Cr Ta alloys [Cr 9.0, 9.2, 9.4, 9.6, 9.8, and 13.0 Ta] (mole fraction, %) were investigated. When Ta content of the alloy is less than 9.4%, there are primary dendrite grains of a Cr solid solution phase existing in the matrix of Cr Cr 2Ta eutectic colonies in the alloy. Moreover, the regular polygon grains of the primary Cr 2Ta Laves phase are surrounded by the Cr Cr 2Ta eutectic colony in the hyper eutectic Cr 9.4% Ta alloys. The scanning electron microphotograph shows that one of the Cr 2Ta phase plates of an eutectic colony always connects with the primary Cr 2Ta Laves phase grain in a hyper eutectic alloy. The eutectic colony size of Cr Ta alloys decreases with increasing Ta. In addition, the macrohardness of Cr Ta alloys is influenced by the chemical composition at room temperature. The binary eutectic Cr Ta alloy presents the lowest hardness on a macrohardness scale.展开更多
基金Project(2013zzts025)supported by the Fundamental Research Funds for the Central Universities of China
文摘Coarse grained WC-9Co cemented carbides with 0-1.0% TaC(mass fraction) were fabricated by HIP-sintering and gas quenching. The effects of TaC on the microstructures and mechanical properties were investigated using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffractometry(XRD) and mechanical properties tests. The results show that the maximum values of hardness and strength are HV 1124 and 2466 MPa respectively when 0.4% TaC is added. When the content of TaC is more than 0.6%, the grain size of WC is no longer affected by the amount of TaC, and(W,Ta)C occurs as well. Moreover, the strength and fracture toughness increase and the(Ta+W) content decreases with the increase of TaC content. The dependence of(Ta+W) content on the mechanical properties indicates that(Ta+W) content in Co should be decreased as low as possible to improve the mechanical properties of coarse grained WC-TaC-9Co cemented carbides with the microstructure of WC+γ two phase regions.
基金supported by the National Science and Technology Major Project(No.J2019-VI-0006-0120)the National Natural Science Foundation of China(No.52074092).
文摘Upon approaching 850℃,the GH4151 alloy exhibits diminished high-temperature strength,primarily attributed to the disruption of γ′phase coherence at elevated temperatures,which reduces its strengthening contribution.Tantalum(Ta)additions enhance the stability of the γ′phase but introduce processing challenges,including pronounced solidification segregation,the formation of secondary phases,and increased susceptibility to cracking during processing.The influence of Ta content on elemental segregation,solidification microstructure,phase precipitation kinetics,and hot deformation behaviour in GH4151 was systematically investigated.Processing windows derived from the dynamic materials model(DMM)and microstructural evolution under varying thermomechanical conditions are further examined.Key findings reveal the severe Ta segregation(segregation coefficient K≈1.608);Ta promotes γ/γ′eutectic and η phase formation,increasing γ′phase volume fraction from 54% to approximately 63%;and increased Ta content elevates flow stress and progressively narrows the DMM-defined processing window;optimized thermomechanical processing parameters(elevated temperatures and strain rates)enhance recrystallization kinetics and hot workability,thereby mitigating cracking propensity.
文摘The dependences of the microstructure and hardness of the binary Cr Ta alloys [Cr 9.0, 9.2, 9.4, 9.6, 9.8, and 13.0 Ta] (mole fraction, %) were investigated. When Ta content of the alloy is less than 9.4%, there are primary dendrite grains of a Cr solid solution phase existing in the matrix of Cr Cr 2Ta eutectic colonies in the alloy. Moreover, the regular polygon grains of the primary Cr 2Ta Laves phase are surrounded by the Cr Cr 2Ta eutectic colony in the hyper eutectic Cr 9.4% Ta alloys. The scanning electron microphotograph shows that one of the Cr 2Ta phase plates of an eutectic colony always connects with the primary Cr 2Ta Laves phase grain in a hyper eutectic alloy. The eutectic colony size of Cr Ta alloys decreases with increasing Ta. In addition, the macrohardness of Cr Ta alloys is influenced by the chemical composition at room temperature. The binary eutectic Cr Ta alloy presents the lowest hardness on a macrohardness scale.
