By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and g...By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and grain sizes of the alloy were determined. It was observed that La greatly promoted growth of columnar grains in as cast structures of the ingots and reduced their diameters. The ingots were subsequently heat treated to obtain well defined fully lamellar structures. The material without La displayed large average size of equiaxed lamellar colonies over 1 400 μm (resulted from five measurement positions in a sample), and the material with 0.1% addition of La consisted of the finest average lamellar colonies as 381 μm, the finest grain size was 337 μm at top position. When La addition was over 0.1%, La stabilized the columnar structure and it was difficult to refine the columnar grains in heat treatment, therefore, grains were coarser.展开更多
Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-ri...Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-rich area shows a slightly higher oxygen content and a much finer grain size.The Ti−Zr alloys present a good combination of high strength(σs=700−900 MPa)and total elongation(>20%),and solid solution strengthening of oxygen plays a major role.Zr does not influence much the oxygen-induced brittleness due to its high structural similarity to Ti.Therefore,the high value of 0.54 wt.%is still within the critical oxygen content for the ductile-to-brittle transition of Ti and does not degrade the ductility.展开更多
文摘By vacuum arc melting, lanthanum (La) was added in the range from 0.05% to 0.3% (mole fraction) to binary Ti 44%Al alloy to refine its fully lamellar (FL) colonies for high ductility. Effects of La on structures and grain sizes of the alloy were determined. It was observed that La greatly promoted growth of columnar grains in as cast structures of the ingots and reduced their diameters. The ingots were subsequently heat treated to obtain well defined fully lamellar structures. The material without La displayed large average size of equiaxed lamellar colonies over 1 400 μm (resulted from five measurement positions in a sample), and the material with 0.1% addition of La consisted of the finest average lamellar colonies as 381 μm, the finest grain size was 337 μm at top position. When La addition was over 0.1%, La stabilized the columnar structure and it was difficult to refine the columnar grains in heat treatment, therefore, grains were coarser.
基金Project(51625404)supported by the National Natural Science Foundation for Distinguished Young Scholar of China。
文摘Ti−Zr alloys(oxygen content 0.42−0.54 wt.%)were prepared via powder metallurgy and hot working.The results indicate that the Ti−Zr alloys exhibit Zr-rich and Zr-lean areas with the sameα-phase structure,and the Zr-rich area shows a slightly higher oxygen content and a much finer grain size.The Ti−Zr alloys present a good combination of high strength(σs=700−900 MPa)and total elongation(>20%),and solid solution strengthening of oxygen plays a major role.Zr does not influence much the oxygen-induced brittleness due to its high structural similarity to Ti.Therefore,the high value of 0.54 wt.%is still within the critical oxygen content for the ductile-to-brittle transition of Ti and does not degrade the ductility.
