In the present work, titanium alloy with a composition of Ti-6.5Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr (TC21) was subjected to plastic deformation and aging processes. A Plastic deformation at room temperature with 2%, 3% and...In the present work, titanium alloy with a composition of Ti-6.5Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr (TC21) was subjected to plastic deformation and aging processes. A Plastic deformation at room temperature with 2%, 3% and 4% stroke strain was applied on the studied samples. Then, the samples aged at 575<span style="white-space:nowrap;">°</span>C for 4 hr. By applying different plastic deformation ratios, the structure revealed an elongated and thin <em>β</em>-phase embedded in an <em>α</em>-phase. Secondary <em>α</em>-platelets were precipitated in the residual <em>β</em>-phase. Maximum hardness (HV440) was obtained for 4% deformed + aged samples. Minimum hardness (HV320) was recorded for the as-cast samples without deformation. The highest ultimate tensile strength of 1311 MPa was obtained for 4% deformed + aged samples due to presence of high amount of dislocation density as well as precipitation of secondary <em>α</em>-platelets in the residual <em>β</em>-phase. The lowest ultimate tensile strength of 1020 MPa was reported for as-cast samples. Maximum elongation of 14% was registered for 4% deformed + aged samples and minimum one of 3% was obtained for as-cast samples. Hence, strain hardening + aging can enhance considerably the elongation of TC21 Ti-alloy up to 366% and 133% in case of applying 4% deformation + aged compared to as-cast and aged samples without applying plastic deformation, respectively.展开更多
This investigation studies the impact strength, tensile strength, hardness, and wear behavior of thin wall austempered and intercritically austempered ductile iron samples with a chemical composition of 3.37% C, 2.7% ...This investigation studies the impact strength, tensile strength, hardness, and wear behavior of thin wall austempered and intercritically austempered ductile iron samples with a chemical composition of 3.37% C, 2.7% Si, 0.30% Mn, 0.01% S, and 0.01% P. The austempered samples were austenitized at 900?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The intercritically austempered samples were sub-austenitized at 810?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The properties of the austempered and intercritically austempered thin wall plates of 5, 10, and 15 mm thickness were evaluated and compared to the as-cast samples. Austempering process affects greatly the tensile properties of all cast thicknesses where ultimate strength reached 1004 MPa for 5-mm thickness. Optimum impact toughness of 40 J was obtained for the austempered samples of 10- and 15-mm thicknesses. The intercritically austempered samples showed properties between the austempered and as-cast samples. Maximum wear resistance was also reported for the austempered samples due to containing retained austenite in the structure which in turn transformed into martensite that increases well the wear resistance. Maximum ultimate strength (1056) MPa and hardness (396 HV) were obtained for 5 mm ADI sample. Maximum impact toughness (43 J) was achieved for 15 mm IADI sample due to existing of pro-eutectoid ferrite in matrix. For all As-cast, ADI and IADI irons, wear resistance decreased with increasing sample thickness. Minimum wear rate (2.22 × 10?6 g/s) was reported for 5-mm ADI sample and maximum one (15.8 × 10?6 g/s) was registered for 15-mm as-cast DI sample, at a sliding speed of 2 m/s.展开更多
<b><span style="font-family:Verdana;">Introduction: </span></b><span style="font-family:Verdana;">It is estimated that about 18% of pregnant women suffer from iron def...<b><span style="font-family:Verdana;">Introduction: </span></b><span style="font-family:Verdana;">It is estimated that about 18% of pregnant women suffer from iron deficiency anemia throughout their whole pregnancy.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">In </span><span style="font-family:Verdana;">twin</span><span style="font-family:Verdana;"> pregnancy, owing to the relatively greater </span><span style="font-family:Verdana;">feto-placental</span><span style="font-family:Verdana;"> requirements and greater expansion in maternal plasma volume </span></span><span style="font-family:Verdana;">and red cell mass, iron requirements </span><span style="font-family:""><span style="font-family:Verdana;">are magnified 1.8 times compared to singleton pregnancies. However, for </span><span style="font-family:Verdana;">prevention</span><span style="font-family:Verdana;"> of iron deficiency in twin </span><span style="font-family:Verdana;">pregnancy</span><span style="font-family:Verdana;">, only sparse data exist regarding the sufficiency of the standard antenatal iron supplementation dose used in singleton pregnancies to meet the increased iron demand. In this study, we investigate the effect of single and double dose iron supplementation for </span><span style="font-family:Verdana;">prevention</span><span style="font-family:Verdana;"> of iron deficiency anemia in twin pregnancy. </span><b><span style="font-family:Verdana;">Methods: </span></b><span style="font-family:Verdana;">A randomized controlled clinical trial was conducted at our center in the period between February 2019 and October 2020,</span></span><span style="font-family:Verdana;"> and</span><span style="font-family:""> <span style="font-family:Verdana;">included</span><span style="font-family:Verdana;"> 450 eligible healthy non-anemic women aged 18 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 35 years, with twin pregnancy at 12 </span><span style=展开更多
文摘In the present work, titanium alloy with a composition of Ti-6.5Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr (TC21) was subjected to plastic deformation and aging processes. A Plastic deformation at room temperature with 2%, 3% and 4% stroke strain was applied on the studied samples. Then, the samples aged at 575<span style="white-space:nowrap;">°</span>C for 4 hr. By applying different plastic deformation ratios, the structure revealed an elongated and thin <em>β</em>-phase embedded in an <em>α</em>-phase. Secondary <em>α</em>-platelets were precipitated in the residual <em>β</em>-phase. Maximum hardness (HV440) was obtained for 4% deformed + aged samples. Minimum hardness (HV320) was recorded for the as-cast samples without deformation. The highest ultimate tensile strength of 1311 MPa was obtained for 4% deformed + aged samples due to presence of high amount of dislocation density as well as precipitation of secondary <em>α</em>-platelets in the residual <em>β</em>-phase. The lowest ultimate tensile strength of 1020 MPa was reported for as-cast samples. Maximum elongation of 14% was registered for 4% deformed + aged samples and minimum one of 3% was obtained for as-cast samples. Hence, strain hardening + aging can enhance considerably the elongation of TC21 Ti-alloy up to 366% and 133% in case of applying 4% deformation + aged compared to as-cast and aged samples without applying plastic deformation, respectively.
文摘This investigation studies the impact strength, tensile strength, hardness, and wear behavior of thin wall austempered and intercritically austempered ductile iron samples with a chemical composition of 3.37% C, 2.7% Si, 0.30% Mn, 0.01% S, and 0.01% P. The austempered samples were austenitized at 900?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The intercritically austempered samples were sub-austenitized at 810?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The properties of the austempered and intercritically austempered thin wall plates of 5, 10, and 15 mm thickness were evaluated and compared to the as-cast samples. Austempering process affects greatly the tensile properties of all cast thicknesses where ultimate strength reached 1004 MPa for 5-mm thickness. Optimum impact toughness of 40 J was obtained for the austempered samples of 10- and 15-mm thicknesses. The intercritically austempered samples showed properties between the austempered and as-cast samples. Maximum wear resistance was also reported for the austempered samples due to containing retained austenite in the structure which in turn transformed into martensite that increases well the wear resistance. Maximum ultimate strength (1056) MPa and hardness (396 HV) were obtained for 5 mm ADI sample. Maximum impact toughness (43 J) was achieved for 15 mm IADI sample due to existing of pro-eutectoid ferrite in matrix. For all As-cast, ADI and IADI irons, wear resistance decreased with increasing sample thickness. Minimum wear rate (2.22 × 10?6 g/s) was reported for 5-mm ADI sample and maximum one (15.8 × 10?6 g/s) was registered for 15-mm as-cast DI sample, at a sliding speed of 2 m/s.
文摘<b><span style="font-family:Verdana;">Introduction: </span></b><span style="font-family:Verdana;">It is estimated that about 18% of pregnant women suffer from iron deficiency anemia throughout their whole pregnancy.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">In </span><span style="font-family:Verdana;">twin</span><span style="font-family:Verdana;"> pregnancy, owing to the relatively greater </span><span style="font-family:Verdana;">feto-placental</span><span style="font-family:Verdana;"> requirements and greater expansion in maternal plasma volume </span></span><span style="font-family:Verdana;">and red cell mass, iron requirements </span><span style="font-family:""><span style="font-family:Verdana;">are magnified 1.8 times compared to singleton pregnancies. However, for </span><span style="font-family:Verdana;">prevention</span><span style="font-family:Verdana;"> of iron deficiency in twin </span><span style="font-family:Verdana;">pregnancy</span><span style="font-family:Verdana;">, only sparse data exist regarding the sufficiency of the standard antenatal iron supplementation dose used in singleton pregnancies to meet the increased iron demand. In this study, we investigate the effect of single and double dose iron supplementation for </span><span style="font-family:Verdana;">prevention</span><span style="font-family:Verdana;"> of iron deficiency anemia in twin pregnancy. </span><b><span style="font-family:Verdana;">Methods: </span></b><span style="font-family:Verdana;">A randomized controlled clinical trial was conducted at our center in the period between February 2019 and October 2020,</span></span><span style="font-family:Verdana;"> and</span><span style="font-family:""> <span style="font-family:Verdana;">included</span><span style="font-family:Verdana;"> 450 eligible healthy non-anemic women aged 18 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 35 years, with twin pregnancy at 12 </span><span style=
