Effect of δ Phase on Microstructure and Hardness of Heat-Affected Zone in TIG-Welded GH4169 Superalloy

The GH4169 superalloy with different content of δ-Ni₃Nb phase was welded by tungsten inert gas welding. A detailed study of microstructure and hardness of heat-affected zone (HAZ) was performed in both as-welded and aged state. The results show that the precipitation of δ phase, especially the intergranular δ phase, can lead to the enrichment of Nb and Mo elements, which promote the formation of γ/Laves eutectic constituent at grain boundaries in HAZ. In as-welded state, the hardness decreases first and then increases (exhibiting a “V” shape) with distance away from fusion line in HAZ, which is governed by grain size. After aging treatment, however, the γ″ phase plays a key role in hardness and leads to the “Λ” shape profiles of hardness in HAZ.     

Effect of the β Phase on Compressive Mechanical Property of CVD Tungsten

采用冷壁化学气相沉积系统,利用H2还原WF6工艺,在纯铜管表面制备获得了高纯钨材料。在440°C沉积温度下,得到具有混合相的钨管,其压缩性能远低于在540°C条件下得到的只具有α相的钨管。由此表明,β-W的出现极大地降低了钨管的压缩性能。在400°C条件下,对具有混合相的钨管进行1h保护气氛退火后,钨管材料中的β相消失,同时其压缩性能与只具有α相的沉积态钨管相近。     

Dissolution kinetics and behavior of δ phase in Inconel 718

1　INTRODUCTIONNi FebasesuperalloyInconel 718,whichisage hardenedbycombinedprecipitationoffineγ′andγ″phasesinausteniticmatrix ,hasbeenwidelyusedforhightemperatureservicessuchasgasturbinedisks .Theamountsof precipitation phasestogetherwiththeirshapeanddistributionhavedeterminantinflu enceonthemechanicalpropertiesofInconel 718.Theprecipitationofintermetallic phasesinInconel718hasbeenintensivelystudied[1,2 ] .Ithasbeenfoundthatthemajorhardeningphaseisγ″ ,andδistheequilibrium phase .…     

Effect of Cd and Sn Addition on the Microstructure and Mechanical Properties of Al-Si-Cu-Mg Cast Alloy

The present work has investigated the effect of trace elements Cd and Sn on the microstructure and mechanical properties of Al-Si-Cu-Mg cast alloy. With the increase of Cd addition the strength of alloy rises at first and then drops. The optimal amount of Cd and Sn addition for AI-Si-Cu-Mg alloy is about 0.27% and 0.1% respectively. Due to the formation of some coarse Cd-rich phases and pure Cd particles the mechanical properties of alloy decrease when Cd amount exceeds 0.27%. When more than 0.1% Sn added, some Sn atoms form low-melting eutectic compound at grain boundary, and then cause over-burning in alloy when solution treated, which may deteriorate properties of alloy, especially ductility of alloy.On the other hand, the addition of Cd and Sn remarkably increases the peak hardness and reduces the time to reach aging peak in Al-Si-Cu-Mg alloy. The action of Cd/Sn in quaternary Al-Si-Cu-Mg alloy is effectively the same as that occur in binary Al-Cu alloy that the enhanced hardening associated with Cd/Sn addition is due to the promotion of the θ‘phase.     

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

The 1.1C–1.5Si–1.1Mn–1.4Cr–0.5Mo–0.6Al–0.6Co(in wt%) steel was treated, respectively, by isothermal austempering process and newly developed austempering–partitioning–tempering process(A–P–T). After austempering at250, 280 and 300 °C for 38, 20 and 10 h, respectively, the sample microstructures were composed of bainitic ferrite plates and film-like retained austenite with thicknesses between 60 and 150 nm. The highest tensile strength of 2003 MPa and hardness value of 53.9 HRC were obtained for the steel after austempering at 250 °C for 38 h, resulting from the combining effect of super-saturated martensite decarburization and stabilization of bainitic formation. After A–P–T treating(heated at 300 °C for 8 h following water cooling, and then heated at 300 °C for 2 h following air cooling),bamboo leaf-like martensite, primary and secondary bainites and retained austenite were observed. The thickness of the secondary bainitic ferrite plates formed during partitioning is much smaller than that of the primary bainite formed during300 °C austempering. Samples subjected to A–P–T treatment showed improvement in ductility compared to that subjected to austempering.     

Effect of the Temperature of Friction Stir Welding on the Microstructure and Mechanical Properties of Welded Joints of an Al – Cu – Mg Alloy

Metal Science and Heat Treatment - A method for assessing the effect of the temperature of friction stir welding on the microstructure and mechanical properties of welded joints of aluminum alloy...     

The Effect of Preliminary Magnetic Activation of an Electrolyte on Its Properties and the Structure of Co–Bi Coatings

Protection of Metals and Physical Chemistry of Surfaces - This paper studies the effect of preliminary magnetohydrodynamic activation of a trilonate electrolyte for the deposition of Co–Bi...     

Effect of Ag on the Microstructure,Mechanical and Bio-corrosion Properties of Fe–30Mn Alloy

In the current work, biodegradable Fe–30 Mn– X Ag( X = 1, 2, 5, 10 wt%) alloys were prepared by the rapid solidifi cation with copper-mold-casting technology. Phase analysis demonstrates that Fe–30 Mn– X Ag alloys consist of austenite γ phase with a fcc structure and martensite ε phase with a hcp structure. The yield strength of the samples increases with increasing Ag contents. Compared with Fe–30 Mn alloy, the degradation rates of Fe–30 Mn– X Ag in Hank's solution are signifi cantly improved. Cytotoxicity evaluation reveals that the Fe–30 Mn–1 Ag and Fe–30 Mn–2 Ag alloys perform less toxicity on the Human Umbilical Vein Endothelial Cells(HUVEC), while Fe–30 Mn–5 Ag and Fe–30 Mn–10 Ag alloys perform no toxicity on it. The contact angles of deionized water on the Fe–30 Mn– X Ag alloy surface were ranged from 55° to 69°, which is benefi cial to the adhesion and growth of the cells. Besides, the addition of Ag leads to a much lower M/H slope, particularly for the Fe–30 Mn–5 Ag alloy exhibiting a non-magnetic property as SS316 L. Therefore, the present Fe–30 Mn– X Ag alloys would be potential candidates for degradable metals.     

Thermal Effect on the Structural and Phase Condition and Mechanical Properties of Ultrafine-Grained Titanium Alloy VT16 in the Temperature Range of 293 – 923 K

Metal Science and Heat Treatment - The effect of pre-recrystallization annealing on the evolution of the structural and phase state and the deformation and fracture behavior of ultrafine-grained...     

Microstructural Effects on the Mechanical Properties of ATI 718Plus<Superscript>®</Superscript> Alloy

Four microstructural variants of ATI 718Plus^® alloy (718Plus) have been investigated to elucidate the effects of grain size, precipitate size, morphology, and phase fraction (δ and γ′) on mechanical properties such as low cycle fatigue (LCF) life, fatigue crack growth rate (FCGR) properties, and dwell FCGR behavior at both 649°C and 704°C under 100 s dwell and nondwell conditions. Similar tests have also been performed on Waspaloy in two comparative microstructural conditions. LCF test results demonstrate that all four microstructural conditions of 718Plus have superior life compared with Waspaloy under all investigated test conditions. FCGR results show that, at both test temperatures, all microstructural conditions of 718Plus and Waspaloy exhibit identical behavior in the steady-state regime, except that 718Plus exhibits a much higher threshold stress intensity (ΔK _TH). However, the dwell FCGR results show that Waspaloy displays better steady-state crack growth resistance under dwell conditions. However, with a thermal exposed precipitate microstructure, 718Plus shows considerable improvement in this response.     

The Effect of Microstructure on the Electrical Properties of Gas-Atomized Copper–Iron Metastable Alloys

With the increase in global demand for highly functionalized materials, there is continued interest in exploiting the material properties of metals either individually or in the form of alloys. Copper–iron alloy is considered unique with its remarkable combination of strength and high electrical conductivity. Due to the low cost of iron, this alloy is expected to replace alloys like Cu–Ag and Cu–Nb. In order to explore the microstructural features, copper–iron alloy with three different compositions (10, 30, and 50 at.% Fe) were prepared by a gas atomization process. A detailed microstructural characterization was performed using scanning electron microscopy, X-ray diffraction, and electron backscattered diffraction. Spark plasma sintering was used to sinter the powders to evaluate their electrical conductivities. The mechanism of the microstructure formation is also discussed in detail. As the Fe content increases, the Fe-rich phase changes its shape from spherical to irregular with a concomitant sharp decrease in the electrical conductivity of the alloy.     

Effect of Strontium and Magnesium Additions on the Microstructure and Mechanical Properties of Al–12Si Alloys

Metals and Materials International - In this study, a binary Al–12Si, eight ternary Al–12Si–Sr, and six quaternary Al–12Si–0.1Sr–(0.2–1)Mg alloys were...     

Effect of Partial Recrystallization on Microstructure and Mechanical Properties for Cross-rolled Molybdenum Sheet

The paper presented here reports an appropriate static heat tretment and analyses the microstructure with different partially recrystallized annealing temperatures of cross-rolled molybdenum sheet in order to improve mechanical property of this type of materials and reduce anisotropy at the same time for perspective application. Five different temperature ranges are chosen in this experiment. The samples of a cross-rolled molybdenum sheet are obtained through powder metallurgy, forged ingots and hot or cold rolled sheet. A period of first-stage annealing at 800℃ for one hour is not qualified for the further processing because of bad plasticity, working hardening and crack on the surface. The appropriate second-stage annealing temperature at 950℃ for one hour is chosen for improving the elongation and reduces yield strength. The results show that this appropriate partially recrystallized annealing treatment has achieved the ideal grain size and mechanical properties when it is compared with the other four different temperatures with the same second-stage annealing conditions.     

Effect of Partial Replacement of Si with Al on the Microstructures and Mechanical Properties of 1000 MPa TRIP Steels

Two newly synthesized C-Mn-Si-Mo-Nb transformation-induced plasticity (TRIP) steels with and without Al addition were designed in order to achieve significant improvements in the mechanical properties. The effect of substitution of Si by Al on tensile properties and the microstructure of cold-rolled C-Mn-Si TRIP steel was investigated under different heat treatments. It was shown that a complex ultrafine microstructure composed of different phases was formed and two types of morphology for ferrite were detected (equiaxial and polygonal). The distribution of alloying elements was observed by using electron probe microanalysis. It was clear that C was concentrated in the retained austenite (RA) and small M/A (austenite/martensite) islands. The Al addition facilitated the formation of polygonal ferrite and increased the stability of the RA. The strain-hardening behavior was studied in detail. All the investigated specimens showed a very high strain-hardening exponent (instantaneous n) but their strain dependence was different. For the C-Mn-Si-Mo-Nb TRIP steel, the maximum n value was achieved when the strain was only about 0.04, while the n value of the Al substituted TRIP steel increased gradually until strains in the range of 0.07-0.10 were reached and the maximum value was achieved. As a result, the elongations of the steel with Al addition increased considerably without obvious deterioration of strength. It was the first time to find microtwinned martensite located between ferrite and bainitic ferrite after tensile deformation in the low alloy TRIP steel with Al.     

Effect of Laser Oscillation on the Microstructure and Mechanical Properties of Laser Melting Deposition Titanium AlloysEI北大核心CSCD

针对激光熔化沉积冶金组织与缺陷,借鉴激光摆动焊接技术,提出一种激光摆动送粉增材制造TC4钛合金工艺,借助激光原位摆动改变熔池运动轨迹进而影响温度梯度和凝固速率,改善增材制造钛合金的微观组织。利用OM、SEM、EBSD和Vickers硬度计研究了激光摆动送粉增材制造工艺对TC4钛合金微观组织演变及力学性能的影响。结果表明,无摆动激光熔化沉积实验的最佳工艺参数为:激光功率1000 W,扫描速率8 mm/s,送粉速率6.92 g/min;直线型激光摆动的最佳工艺参数为:摆动频率200 Hz,摆动幅度1.5 mm。直线型激光摆动对熔池形貌改善显著,气孔和裂纹等缺陷较少,柱状晶数量和尺寸均有所减小,并且晶粒出现了等轴化的现象。相比无摆动样品,激光摆动后Ti-6Al-4V合金单道区域平均晶粒尺寸从5.20μm减小到4.37μm;硬度从418.00 HV提升到428.75 HV。     

Effect of Extrusion Temperature on the Microstructure and Mechanical Properties of Mg–5Al–2Ca Alloy

In this work, the Mg–5Al–2Ca alloy was extruded at 573, 623 and 673 K, with a ratio of 16:1 and a constant speed of 3 mm/s. Results demonstrate that the Al2Ca particle is formed in Mg–5Al–2Ca alloy. The size, amount and distribution of Al2Ca particles are influenced evidently by extrusion temperature. Unlike previous reports, the intensity of basal texture increases with increasing extrusion temperature, and the reasons are analyzed and given. Even though the average grain size increases as the extrusion temperature increased from 573 to 623 K, the YS, UTS and elongation of asextruded Mg–5Al–2Ca alloy are almost kept the same at 573 and 623 K. The reason is speculated as the balance of grain size, Al2Ca phase and texture at the two temperatures. The work hardening rate depends on extrusion temperature, and the largest θ value of Mg–5Al–2Ca alloy is obtained when the extrusion was performed at 623 K.     

Effects of Zr and Y on the Mechanical Properties and the Microstructure of Ti-Al-Sn-Nb-Mo-Si Alloy

In the present paper the effects of additions of Zr and Y on the microstructure and mechanical properties for Ti-(6.06.5)Al-(2.0～3.0)Sn-(1.5～6.0)Zr-(0.8～1.0)Mo-1.0Nb-0.25Si alloys are reported,The experimental results show that: with in-creasing of Zr content,tensile strength and creep resistance of the alloys increase,and reduction in area and thermal stability ofthe alloys decrease.Decrease in thermal stabiIity of the alloys mainly caused by surface thermal unstability.After heat treatmentY addition can make grain size of the alloys refine.The reduction in area and thermal stability of the alloys with Y addition areimproved,and tensile strength slightly decreases and creep resistance is essentially the same as the alloy without Y addition.Thesephenomena are explained in brief.     

Effects of δ phase and cold drawing ratio on the LCF properties of alloy 718 wire

The effects of the amount and distribution of δ particles on the low cycle fatigue (LCF) properties of alloy 718 wire were investigated. The amount and distribution of δ particles were controlled by cold drawing followed by a variety of agings. As the cold drawing ratio and aging time at 1116K increased, the well developed granular δ particles increased in amount and their distribution at grain/twin boundaries became more uniform. Regardless of the aging conditions, the LCF life increased as the cold drawing ratio increased. The granular particles precipitated along the grain boundary also improved the LCF life of alloy 718 wire since they inhibited crack propagation. After Merrick heat treatment, 50% of the cold drawn wire displayed lower 698K tensile and yield strength than 30% of the cold drawn wire. This was because the higher strain induced by the cold drawing prior to the first aging at 1116K appeared to promote the precipitation of the δ phase during aging, which has no influence on the strength of the material but has same stoichiometry with the γ phase as Ni₃Nb and, as a result, the higher strain precipitated a smaller quantity of γ particles with subsequent aging, which is a major hardening phase of the alloy. Cold drawing also lowered the precipitation temperature of the δ phase.