Wrought and laser powder bed fusion(LPBF)Ti−6Al−4V(Ti-6-4)specimens were comparatively evaluated,with the objective to determine LPBF Ti−6Al−4V’s suitability for biomedical applications.Testing included nanoindentati...Wrought and laser powder bed fusion(LPBF)Ti−6Al−4V(Ti-6-4)specimens were comparatively evaluated,with the objective to determine LPBF Ti−6Al−4V’s suitability for biomedical applications.Testing included nanoindentation,cyclic polarization in simulated body fluid(SBF,37°C),and dry and SBF“ball-on-plate”sliding.Wrought Ti-6-4 exhibited a lamellarα+βmicrostructure,whereas LPBF Ti-6-4 displayed a fine-grainedα′-martensite microstructure.LPBF Ti-6-4 demonstrated~3%higher indentation modulus and~32%higher hardness,while wrought Ti-6-4 showed~8%higher plasticity.Both alloys exhibited low corrosion rates(10−5 mA/cm^(2)order)and true passivity(10−4 mA/cm^(2)order).No localized corrosion was observed in either two alloys,except for occasional metastable pitting in the LPBF alloy.However,LPBF Ti-6-4 presented higher corrosion rate and passive current,ascribed to its martensitic structure.During dry sliding,LPBF Ti-6-4 exhibited~14%lower volume loss compared to wrought Ti-6-4.Sliding in SBF increased volume losses for both alloys,with wear resistances nearly equalized,as the advantage of LPBF Ti-6-4 decreased due to more intense wear-accelerated corrosion induced by the stressed martensite.Overall,the results demonstrate the suitability of LPBF Ti-6-4 for biomedical uses.展开更多
The novel cast irons of chemical composition(wt%)0.7C-5W-5Mo-5V-10Cr-2.5Ti were invented with the additions of 1.6wt%B and 2.7wt%B.The aim of this work was to study the effect of boron on the structural state of the a...The novel cast irons of chemical composition(wt%)0.7C-5W-5Mo-5V-10Cr-2.5Ti were invented with the additions of 1.6wt%B and 2.7wt%B.The aim of this work was to study the effect of boron on the structural state of the alloys and phase elemental distribution with respect to the formation of wear-resistant structural constituents.It was found that the alloy containing 1.6wt%B was composed of three eutectics:(a)“M_(2)(C,B)_(5)+ferrite”having a“Chinese Script”morphology(89.8vol%),(b)“M_(7)(C,B)_(3)+Austenite”having a“Rosette”morphology,and(c)“M_(3)C+Austenite”having a“Ledeburite”-shaped morphology(2.7vol%).With 2.7wt%of boron content,the bulk hardness increased from HRC 31 to HRC 38.5.The primary carboborides M_(2)(C,B)_(5) with average microhardness of HV 2797 appeared in the structure with a volume fraction of 17.6vol%.The volume fraction of eutectics(a)and(b,c)decreased to 71.2vol%and 3.9vol%,respectively.The matrix was“ferrite/austenite”for 1.6wt%B and“ferrite/pearlite”for 2.7wt%B.Both cast irons contained compact precipitates of carbide(Ti,M)C and carboboride(Ti,M)(C,В)with a volume fraction of 7.3%-7.5%.Based on the energy-dispersive X-ray spectroscopy,the elemental phase distributions and the appropriate phase formulas are presented in this work.展开更多
The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbide...The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.展开更多
Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium（5.0wt%–10.0wt%） and chromium（up to 9.0wt%） contents. The ...Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium（5.0wt%–10.0wt%） and chromium（up to 9.0wt%） contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides（M7C3） and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.展开更多
基金supported by the Ministry of Education and Science of Ukraine(No.0123U101834)support in the framework of the“EU Next generation EU through the Recovery and Resilience Plan for Slovakia”(Nos.09I03-03-V01-00061 and 09I03-03-V01-00099)。
文摘Wrought and laser powder bed fusion(LPBF)Ti−6Al−4V(Ti-6-4)specimens were comparatively evaluated,with the objective to determine LPBF Ti−6Al−4V’s suitability for biomedical applications.Testing included nanoindentation,cyclic polarization in simulated body fluid(SBF,37°C),and dry and SBF“ball-on-plate”sliding.Wrought Ti-6-4 exhibited a lamellarα+βmicrostructure,whereas LPBF Ti-6-4 displayed a fine-grainedα′-martensite microstructure.LPBF Ti-6-4 demonstrated~3%higher indentation modulus and~32%higher hardness,while wrought Ti-6-4 showed~8%higher plasticity.Both alloys exhibited low corrosion rates(10−5 mA/cm^(2)order)and true passivity(10−4 mA/cm^(2)order).No localized corrosion was observed in either two alloys,except for occasional metastable pitting in the LPBF alloy.However,LPBF Ti-6-4 presented higher corrosion rate and passive current,ascribed to its martensitic structure.During dry sliding,LPBF Ti-6-4 exhibited~14%lower volume loss compared to wrought Ti-6-4.Sliding in SBF increased volume losses for both alloys,with wear resistances nearly equalized,as the advantage of LPBF Ti-6-4 decreased due to more intense wear-accelerated corrosion induced by the stressed martensite.Overall,the results demonstrate the suitability of LPBF Ti-6-4 for biomedical uses.
基金This work was financially supported by Ministry of Edu-cation and Science of Ukraine under the project No 0119U100080.
文摘The novel cast irons of chemical composition(wt%)0.7C-5W-5Mo-5V-10Cr-2.5Ti were invented with the additions of 1.6wt%B and 2.7wt%B.The aim of this work was to study the effect of boron on the structural state of the alloys and phase elemental distribution with respect to the formation of wear-resistant structural constituents.It was found that the alloy containing 1.6wt%B was composed of three eutectics:(a)“M_(2)(C,B)_(5)+ferrite”having a“Chinese Script”morphology(89.8vol%),(b)“M_(7)(C,B)_(3)+Austenite”having a“Rosette”morphology,and(c)“M_(3)C+Austenite”having a“Ledeburite”-shaped morphology(2.7vol%).With 2.7wt%of boron content,the bulk hardness increased from HRC 31 to HRC 38.5.The primary carboborides M_(2)(C,B)_(5) with average microhardness of HV 2797 appeared in the structure with a volume fraction of 17.6vol%.The volume fraction of eutectics(a)and(b,c)decreased to 71.2vol%and 3.9vol%,respectively.The matrix was“ferrite/austenite”for 1.6wt%B and“ferrite/pearlite”for 2.7wt%B.Both cast irons contained compact precipitates of carbide(Ti,M)C and carboboride(Ti,M)(C,В)with a volume fraction of 7.3%-7.5%.Based on the energy-dispersive X-ray spectroscopy,the elemental phase distributions and the appropriate phase formulas are presented in this work.
基金the Muroran Institute of Technology for funding this project
文摘The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.
文摘Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C–4wt%Mn–1.5wt%Ni spheroidal carbide cast irons with varying vanadium（5.0wt%–10.0wt%） and chromium（up to 9.0wt%） contents. The alloys were quenched at 920℃. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides（M7C3） and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%–10.0wt% for V and 2.5wt%–4.5wt% for Cr, which corresponds to the alloys containing 9vol%–15vol% spheroidal VC carbides, 8vol%–16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9–2.3 times that of the traditional 12wt% V–13wt% Mn spheroidal carbide cast iron.
