Effect Of Swaging Research Articles

Effect of swaging on microstructure and mechanical properties of W-Ni-Co alloys

The effect of deformation during warm swaging on mechanical properties of W-Ni-Co alloys was investigated. The alloys, based on 92%W with Ni/Co ratio of 7/3 and 8/2, were processed through liquid phase sintering followed by heat treatment and swaging. Multistep swaging deformation at 400 °C leads to increase in strength at the expense of ductility. For a given deformation, the alloy with 7/3 NiCo shows higher strength and lower ductility as compared to the alloy with 8/2 NiCo ratio. This is attributed to the presence of fine W precipitates (0.2–0.3%) in the matrix phase, which is relatively more in 7/3. Higher ductility of the 8/2 alloy is characterized by shear lip failure of the matrix in contrast to shallow dimple failure of the matrix in 7/3 and this appears to be consistent with the presence of fine, undeformable W precipitates in the matrix phase. The analysis of work hardening shows a three slope behaviour in the heat treated condition where as the swaged specimens show a single slope behaviour. This has been explained in terms of deformation of softer matrix in the initial stage (Stage I and II) and that of the two phase aggregate later (Stage III). The results are discussed in relation to the studies carried out on similar alloys.

Effect of rotary swaging and subsequent annealing on microstructure and mechanical properties of W-1.5ZrO2 alloys

W-1.5ZrO2 alloy bars with two diameters, named as D9 and D5, were prepared by liquid phase method and rotary swaging method. The effects of swaging and annealing on the microstructure and mechanical properties of tungsten alloys were investigated. Under the same swaging ratio, the compressive strength of D5 tungsten alloy and D9 tungsten alloy is 23.27% and 22.37% higty her than that of pure W, respectively. After multi-pass swaging, the diameter of tungsten alloy decreased from 9 mm to 5 mm, and the hardness and compressive strength increased by 14.6% and 21.93%, respectively. After multi-pass rotary swaging, the diameter of tungsten alloy is reduced from 9 mm to 5 mm, and the hardness and compressive strength are increased by 14.6% and 21.93% respectively. The fracture mode has gradually changed from intergranular fracture to trans-granular fracture. Therefore, the strength of tungsten alloy can be improved by adding zirconia and proper swaging process. With the increase of annealing temperature or time, recrystallization and grain growth will be caused. The addition of ZrO2 can delay the recrystallization of tungsten alloy during annealing, and inhibit grain growth. When the annealing temperature is lower than 1200 °C, the compressive strength of tungsten alloy remains unchanged, while the failure strain increases. After annealing at 1500 °C, the strength and failure strain of tungsten alloy decreased by 18.9% and 35.7% respectively. In order to obtain excellent strength and toughness, annealing at 1100–1200 °C for 1 h can be chosen for W-1.5ZrO2 alloy.

Effects of swaging and annealing on the microstructure and mechanical properties of ZrC dispersion-strengthened tungsten

Nano-sized ZrC dispersion strengthened tungsten alloy (W-0.5wt%ZrC) rods with enhanced mechanical properties and superior high-temperature stability were fabricated by high temperature rotary swaging. The effects of swaging and annealing on the microstructure and mechanical properties of W-0.5wt%ZrC alloys were investigated. The as-swaged W-0.5%ZrC rod showed noticeable ductility at 200 °C with a total elongation of 4.2% and a tensile strength of 724 MPa, and at 500 °C the strength remains as high as 547 MPa and the total elongation is 28%. The ductile-to-brittle transition temperature (DBTT) is about 200 °C. The recrystallization start temperature of swaged W-0.5wt%ZrC is about 1500 °C, which is about 300 °C higher than that of rolled pure W. The possible mechanisms for the enhanced mechanical properties and thermal stability were discussed.

Effect of swaging and aging heat treatment on microstructure and mechanical properties of tungsten heavy alloy

In the present study, a 90W-6Ni-2Fe-2Co (Wt.%) tungsten heavy alloy was processed through liquid phase sintering route, followed by vacuum heat treatment and swaging. Further, ageing was carried out at 700° C for three different time period, in order to improve mechanical properties. Microstructural analysis showed decrease in contiguity levels from sintered to swaged condition. Swaging improved the tensile strength of the alloy at the expense of ductility and impact. Aging of the swaged alloys showed further improvement in yield, tensile strength and hardness of the alloy with concomitant loss of ductility and impact toughness. The fracture surface of sintered alloy exhibited brittle failure features consisting of tungsten-matrix and tungsten-tungsten failure. However, the heat treated alloy showed lesser intergranular failure indicating higher ductility. The swaged alloy exhibited relatively higher fraction of transgranular cleavage features. The study shows that the heat treatment (that includes solution heat treatment and ageing) and swaging can be used judiciously to tailor the final mechanical properties of the tungsten heavy alloys.

Effect of swaging and rolling post sintering treatments on the corrosion behaviour of Alumix 321 PM alloy

In this work, two post sintering hot deformation processes were applied on Alumix 321 PM alloy which is a commercially available aluminum powder alloy which can be considered equivalent to the wrought AA6061 alloy. The powder was compacted, sintered, and then either hot swaged or hot rolled. The results show that both hardness and density were improved as a result of the applied post sintering treatment. Theoretical density (TD) of 99.1% and 99.39% were recorded for the hot rolled and hot swaged alloys, respectively. T6 hardness improves to 106±6 HRE and 96±2 HRE for hot rolled and hot swaged alloys, respectively. The performance was assessed in terms of corrosion behaviour by testing the Alumix 321 PM alloy in as sintered, and as hot deformed conditions after exposure to 3.5wt% NaCl solution. Electrochemical techniques were used to study the effect of hot deformation on corrosion behaviour. Corrosion current density decreases as a result of hot swaging and hot rolling and in both cases the values were less than those of the wrought counterpart, AA6061 alloy. The stair step polarization was applied; the results obtained support that the technique seems promising to bridge the gap between traditional and accelerated corrosion test methods. Pitting was the main corrosion mechanism for the wrought alloy while, pitting, crevice, and intergranular corrosion were observed for the PM alloys.

Effect of swaging on microstructure and mechanical properties of liquid-phase sintered 93W-4.9(Ni, Co)-2.1Fe alloy

The effect of swaging on the microstructure and mechanical properties of 93W-4.9Ni-2.1Fe alloy was investigated. The alloy was prepared by liquid-phase sintering under hydrogen atmosphere followed by vacuum heat treatment and swaging at 600°C with different area reductions (ranging from 15.0% to 84.8%). The as-swaged alloy with area reduction 84.8% exhibits the highest ultimate tensile strength (about 1490MPa) and the lowest elongation (about 2.5%), which has been attributed to higher fraction of tungsten cleavage. For the as-sintered alloys, the fracture modes are a combination of the ductile rupture of W-Ni-Fe-Co matrix, transgranular cleavage of the tungsten particles, W-W interfacial segregation and W-M interfacial debonding, whereas transgranular cleavage of the tungsten particles is the main characteristic in the as-swaged alloy. Transmission electron microscopy images indicate that tungsten grains and W-Ni-Fe-Co matrix phase are composed of high-density dislocations. Based on the results, when running the swaging of 93W-4.9(Ni, Co)-2.1Fe alloy at 600°C, the strengthening mechanism can be mainly due to the working-hardening.

Effect of swaging on Young׳s modulus of β Ti–33.6Nb–4Sn alloy

The effect of swaging on the Young's modulus of β Ti–33.6Nb–4Sn rods was investigated by X-ray diffraction, thermography, microstructural observations, deformation simulator analysis and cyclic tensile deformation. Stress-induced α″ martensite was stabilized by swaging, dependent on the diameter reduction rate during swaging. Thermography and deformation simulator analysis revealed that swaged rods were adiabatically heated, and consequently, stress-induced α″ underwent reverse transformation. Young's modulus, which was measured by the slope of the initial portion of the stress–strain curve, decreased from 56GPa in the hot-forged/quenched rod to 44GPa in the rapidly swaged rod with a high reduction rate and to 45GPa in the gradually swaged rod with a low reduction rate. The tangent modulus, which was measured by the slope of the tangent to any point on the stress–strain curve, decreased with strain even in the linear range of the stress–strain curve of the hot-forged/quenched rod and the rapidly swaged rod, while the tangent modulus remained unchanged for the gradually swaged rod. It was found that Young's moduli in swaged β Ti–33.6Nb–4Sn rods were affected by stabilized α″ martensite. Low Young's modulus of 45GPa and high strength over 800MPa were obtained when the reverse transformation by adiabatic heating was suppressed and the stress-induced α″ was sufficiently stabilized by gradual swaging to a 75% reduction in cross section area.

Effects of Swaging and Aluminium Content on the Microstructure and Mechanical and Sliding Wear Properties of Zinc-Based Alloys

An attempt has been made to examine the influence of swaging on the microstructure, mechanical properties and sliding wear characteristics of some zinc-based alloys comprising varying concentrations of aluminium. The density of the alloys decreased with aluminium content while hardness followed a reverse trend. Further, the aluminium concentration in an intermediate range (close to 27.5%) led the alloy system to attain maximum tensile properties and sliding wear resistance. Swaged specimens exhibited properties superior to their as-cast variety irrespective of the test condition and aluminium content.

Effect of swaging on the 1000?C compressive slow plastic flow characteristics of the directionally solidified eutectic alloy ?/?'?-?

Swaging between 750 and 1050‡ C has been investigated as a means to introduce work into the directionally solidified eutectic alloy γ/gg′-α (Ni-32.3 wt % Mo-6.3 wt % Al) and increase the elevated temperature creep strength. The 1000‡ C slow plastic compressive flow stress-strain rate properties in air of as-grown, annealed, and worked nominally 10 and 25% materials have been determined. Swaging did not improve the slow plastic behaviour. In fact large reductions tended to degrade the strength and produced a change in the deformation mechanism from uniform flow to one involving intense slip band formation. Comparison of 1000‡ C tensile and compressive strength-strain rate data reveals that deformation is independent of the stress state.