Influence of heat treatment on tribological behaviors of novel wrought aluminum bronze

Influence of heat treatment on mechanical properties and tribological behaviors of Ti and B modified wrought aluminum bronze were studied. The results show that different strength and plasticity combination of the alloy after solution treatment can be obtained by adjusting the ageing temperature. When aged at 450?℃, the tensile strength σ b, yield strength σ 0.2 , elongation δ and hardness of the alloy are 1?050?MPa, 780?MPa, 4.5%, HB282, respectively. When aged at 650?℃, those of the alloy are 905?MPa, 600?MPa, 12%, HB232, respectively. Under boundary lubrication condition with pressure above 22.2?MPa, alloy with low temperature ageing has the best wear property. However, under the condition involving impact or shock loading, alloy with high temperature ageing is preferable. If the load is not heavy, the alloy under extrusion state is favorable for wear resisting parts.

Effects of zincate treatment on adhesion of electroless Ni-P coating onto various aluminum alloys

The effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrates were examined.Surface morphology of zinc deposits in the 1st zincate treatment and its adhesion were changed depending on the alloying element.The zinc deposits in the 2nd zincate treatment became thinly uniform,and the adhesion between aluminum alloy substrate and Ni-P coating was improved irrespective of the alloying element.XPS analysis revealed the existence of zinc on the surface of each aluminum alloy substrate after the pickling in 5% nitric acid.This zinc on the surface should be an important factor influencing the morphology of zinc deposit at the 2nd zincate treatment and its adhesion.

Strengthening-toughening of 7xxx series high strength aluminum alloys by heat treatment

The effects of stepped solution heat treatments on the dissolution of soluble remnant constituents and mechanical properties of 7055 aluminum alloy were investigated. It was shown that a suitable pretreatment at lower temperature can enable complete dissolution of the constituent particles in 7055 alloy without overheating by subsequent high temperature solution treatment. This in turn increased the tensile strength and fracture toughness of 7055 alloy to 805 MPa and 41.5 MPa·m 1/2 respectively, with approximately 9% tensile elongation. The near solvus pre precipitation following after high temperature solution treatment was also studied on 7055 aluminum alloy. The effect of the pre precipitation on the microstructure, age hardening and stress corrosion cracking of 7055 alloy was investigated. The optical and transimission electron microscopy observation show that the near solvus pre precipitation can be limited to grain boundary and enhance the discontinuity of grain boundary precipitates in the subsequent ageing. The stress corrosion cracking resistance of aged 7055 alloy can be improved via the pre precipitation with non deteriorated strength and plasticity.

Effect of heat treatment on microstructure and properties of hot-extruded nickel-aluminum bronze

The effect of heat treatment on the microstructure and properties of a hot-extruded nickel-aluminum bronze was investigated. Experimental materials were heat treated through different processes, including quenching, normalizing, aging and annealing, and their microstructure, corrosion resistance and mechanical properties were characterized. It is found that quenching causes all β phase transformed into β′ phase, however, normalizing causes β phase transformed into β′, α and κ phases. When the quenched sample is aged, fine к phase is precipitated from the as-quenched microstructure of β′ phase. Annealing causes the transformation of β′ into α and к phases. The results of mechanical property tests show that quenching, normalizing and aging improve the tensile strength and hardness of the experimental material, with a corresponding fall in elongation. Annealing raises the elongation but reduces the tensile strength and hardness. Furthermore, corrosion resistance of nickel-aluminum bronze ranks from worse to better in the following order: aged, quenched, normalized, hot-extruded and annealed. However, with the exposure time of corrosion test increasing, the difference of average corrosion rate between those nickel-aluminum bronzes turns small.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Si Cp/2024 Aluminum Matrix Composite

SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.

Effects of heat treatment on dynamic compressive properties and energy absorption characteristics of open-cell aluminum alloy foams

The effects of heat treatment on the dynamic compressive properties and energy absorption characteristics of open cell aluminum alloy foams (Al-Mg-Si alloy foam and Al-Cu-Mg alloy foam) produced by infiltrating process were studied. Two kinds of heat treatment were exploited: age-hardening and solution heat treating plus age-hardening (T6). The split Hopkinson pressure bar (SHPB) was used for high strain rate compression test. The results show that both age-hardened and T6-strengthened foams exhibit improved compression strength and shortened plateau region compared with that of foams in as-fabricated state under high strain rate compression, and the energy absorption capacity is also influenced significantly by heat treatment. It is worthy to note that omitting the solution treating can also improve the strength and energy absorbed much.

Plasma Treatment of Aluminum Using a Surface Barrier Discharge Operated in Air and Nitrogen: Parameter Optimization and Related Effects

This paper presents the results of aluminum surface treatment by diffuse coplanar surface barrier discharge. The goals are to study the effectiveness of the plasma treatment and the dependence of its efficiency on operation parameters, such as sample-to-electrode distance, treatment time or gas atmosphere. Three types of aluminum materials （bricks, sheets and thin films） were tested to ensure the reliability of the treatment. The changes in the surface properties were characterized by the surface free energy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy （ATR FTIR） and X-ray photoelectron spec- troscopy （XPS）. The influence of aging effect on the treatment was also measured and discussed.

EFFECTS OF HEAT TREATMENT ON THE THERMAL EXPANSION BEHAVIOR OF SiC WHISKER REINFORCED ALUMINUM COMPOSITE

The thermal expansion behaviors of commercially-available SiC whisker reinforced pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors were greatly affected by heat treatment. To explain the results, the microstructures and thermal mismatch stresses in the matrix of the composite were examined by the transmission electron microscope and X-ray diffraction, respectively. The results show that the dislocation density and thermal mismatch stresses in the matrix of the composites water-quenched from 600°C are much higher than those of the composite slowly cooled from 600°C. The analysis suggests that the coefficients of thermal expansion (CTE) are closely related to the change of thermal mismatch stresses and the yield strength of the matrix of the composite. The comparison of the coefficients of thermal expansion between experiments and calculations suggests that the temperature behaviors of CTE of SiC/Al composite agree better with those of Kerner's model within lower temperature range.

Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil

This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces.The results of our study showed that the state of the topmost surface layer（i.e.the surface morphology and chemical groups）of plasma modified aluminum significantly depends on the chemical precleaning.Commonly used chemicals（isopropanol,trichlorethane,solution of Na OH in deionized water）were used as precleaning agents.The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University,which operates in Ar,Ar/O_2 gas mixtures.The effectiveness of the plasma treatment was estimated by the wettability measurements,showing high wettability improvement already after 0.3 s treatment.The effects of surface cleaning（hydrocarbon removal）,surface oxidation and activation（generation of OH groups）were estimated using infrared spectroscopy.The changes in the surface morphology were measured using scanning electron microscopy.Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.

Densification of Thin Aluminum Oxide Films by Thermal Treatments

Thin AlOx films were grown on 4H-SiC by plasma-assisted atomic layer deposition (ALD) and plasma assisted electron-beam evaporation at 300°C. After deposition, the films were annealed in nitrogen at temperatures between 500°C and 1050°C. The films were analyzed by X-ray reflectivity (XRR) and atomic force microscopy (AFM) in order to determine film thickness, surface roughness and density of the AlOx layer. No differences were found in the behavior of AlOx films upon annealing for the two different employed deposition techniques. Annealing results in film densification, which is most prominent above the crystallization temperature (800°C). In addition to the increasing density, a mass loss of ~5% was determined and attributed to the presence of aluminum oxyhydroxide in as deposited films. All changes in film properties after high temperature annealing appear to be independent of the deposition technique.

Influence of melt-treatment on material constants of aluminum sheet used for easy-open can during hot deformation

The isothermal compression test at elevated temperature was carried out for aluminum sheets prepared by different melt-treatment methods with aid of dynamic hot/mechanical simulation experimental technology. The material constants of hot deformation have been solved by multivariate regression directly. Influence of metallurgy factors on the constants was analyzed. The results show that at some strain, the relationship of sheets’ flow stress with deformation temperature and strain rate can be expressed more suitably with Arrhenius equation modified by hyperbolic sine function. Structure factor A1, stress-level coefficient α, strain rate sensibility exponent m and deformation activation energy Q all increase with increment of strain, while stress exponent n decreases gradually. The bigger α value or the smaller n value is, the more obvious the dynamic softening is, but the α value will increase for the metallurgy defects existing in the sheets. Influence of melt-treatment on Q depends upon the synthesis effect of all kinds of metallurgy defects. The Q and n values of the sheet prepared by high-efficient melt-treatment are the least, while the m value is the biggest, and the sheet can deform easily and evenly.

Effect of heat-treatment on microstructure and properties of SiC particulate-reinforced aluminum matrix composite

The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fine grains and homogeneous microstructures can be obtained,the average grain size of the as-solid solution treated and as-aged composites after extrusion is under 3.0 μm. A large amount of the Cu-rich phase particles form in the as-extruded samples,and solve into the matrix after solid solution treatment. After aging,the size of the precipitate phases,mainly MgZn2 and CuAl2 is less than 1.0 μm,which homogeneously distribute inside the grains and at the grain boundaries. The ultimate tensile strength of the composite treated at T6 state,i.e. solid solution treated at 475 ℃ for 1 h then aged at 120 ℃ for 24 h,is up to 765 MPa.

均匀化温度对5052铝合金显微组织和性能的影响

对5052铝合金铸锭进行了520~580℃保温20 h空冷的均匀化处理,随后检测了合金的显微组织、力学性能和电化学性能,以揭示均匀化温度对合金显微组织和性能的影响。结果表明:5052铝合金的最佳均匀化工艺为560℃保温20 h后空冷,经此工艺均匀化处理的5052铝合金中Al_(3)Fe相的析出明显减少、塑性提升,其抗拉强度为193.4 MPa,断后伸长率为24.4%,在体积分数为3.5%的NaCl溶液中的自腐蚀电位为-1.202 V,自腐蚀电流密度为8.664×10^(-6)A·cm^(2),耐蚀性最优。均匀化处理能明显减少Al_(3)Fe相的析出,降低合金晶间腐蚀倾向。

固溶时效处理对QAl10-3-1.5合金力学及摩擦磨损性能的影响

采用MFT-5000Rtec摩擦磨损试验机研究了QAl10-3-1.5合金挤制态和时效态在干滑动条件下的摩擦磨损行为,利用轮廓仪、金相显微镜和X-射线衍射仪等对QAl10-3-1.5合金组织特征和摩擦磨损机制进行了分析。结果表明:挤制态试样的抗拉强度约为680 MPa,经850℃×60 min(水冷)+550℃×4 h固溶时效处理后,抗拉强度提高了60 MPa,断后伸长率提高了1%,布氏硬度由136 HBW增至160 HBW;在10,20,30 N载荷下,挤制态试样在循环载荷作用下出现大量剥落,平均摩擦系数比时效态试样低10%左右;时效态试样磨斑宽度和磨斑深度均比挤制态试样小,耐磨性明显提高,且载荷越大,耐磨性提高越显著。

晶粒细化对免热处理压铸铝合金组织与性能的影响

采用光学显微镜和电子拉伸试验机,研究了晶粒细化对免热处理压铸铝合金显微组织、流动性和力学性能的影响。结果表明:随着铝钛硼合金添加量的逐渐增加,压铸铝合金的α-Al晶粒逐渐从粗大的树枝状细化成细小的颗粒状和近球形状,压铸铝合金的流动性试样长度、抗拉强度和断后伸长率逐渐升高。添加0.25%的铝钛硼合金,压铸铝合金的流动性试样长度为947 mm,抗拉强度为295.6 MPa,断后伸长率为8.5%,与未添加铝钛硼合金相比,压铸铝合金的流动性试样的长度增加了10.9%,抗拉强度提高了7.1%,断后伸长率提高了14.9%。

一体压铸用免热处理铝合金自主研发及应用

为获得性能优异的一体压铸用免热处理铝合金,通过调整合金中各元素的质量分数,设计出3种不同成分比例的Al-Si系免热处理铝合金,采用差示扫描量热仪(DSC)、金相显微镜、扫描电镜、拉伸试验机和电磁共振式疲劳试验机对3种合金的熔化温度区间、组织相构成、断口形貌、拉伸与疲劳性能进行分析,结果表明,2#合金的熔化温度区间为55℃,抗拉强度、屈服强度、断后伸长率分别为303 MPa、153 MPa、11.3%,在1×10^(7)循环周次下的轴向拉压疲劳强度均值为125 MPa,因此,2#合金具有良好的铸造流动性、金相组织、强韧综合性能与铸造工艺性,且疲劳性能优于汽车行业普遍应用的AlSi9Cu3(Fe)压铸合金。

Microstructure and mechanical properties of forged Al-7.1Zn-1.1Mg-1.6Cu-0.14Zr alloy after two-step ageing treatment at 120 and 170℃

The tensile properties, electrical conductivity, and microstructure of the forged A1-7.1Zn-1.1Mg-1.6Cu-0.14Zr alloy were investigated after a two-step ageing treatment at 120 and 170℃. The results indicate that the strength of the alloy reaches the peak value at 170~C for 1 h during the second step ageing and then decreases sharply. However, the electrical conductivity value increases continuously with the second ageing time increasing. The fracture mechanism of the alloy is intergranular fracture for 1 h and then changes to dimple transgranular fracture later, and the toughness of the alloy is improved significantly. The phases of rl＇ and 1＂1 are major precipitates in the alloy under the two-step ageing condition. Discontinuous grain boundary precipitates and precipitate-flee zones along the grain boundary are clearly observed.

Deep-cryogenic-treatment-induced phase transformation in the Al-Zn-Mg-Cu alloy

An aluminum alloy （Al-Zn-Mg-Cu） subjected to deep cryogenic treatment （DCT） was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affects the mechanical properties of the Al alloy. Both Guinier-Preston （GP） zones and a metastableη′phase were observed by high-resolution transmission electron microscopy. The phenomenon of the second precipitation of the GP zones in samples subjected to DCT after being aged was observed. The viability of this phase transfor-mation was also demonstrated by first-principles calculations.

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560℃ for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180℃. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420℃, and then increased;the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180℃ rolling water-quenched alloy were also improved by the presence ofβ″phase. Above 420℃, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.

Effects of solution heat treatment on corrosion resistance of 5083F Al alloy

Aluminum alloys are used as substitutes for fiber reinforced polymer(FRP) in ships and boats.However,ships constructed with 5000-series Al alloy suffer a little corrosion in the marine environment,when they run in high speed,and high flow rate,etc.Therefore,solution heat treatment was carried out to prevent corrosion.The optimal heat treatment involved heating specimens for 120 min at 420 ℃ and then cooling them in water.In addition,the optimal ageing condition involved ageing specimens for 240 min at 180 ℃.The slow strain rate test(SSRT) in a seawater revealed that heat treatment under optimal conditions produced improved elongation,time-to-fracture and amount of dimples compared with the as-received specimen.