Influence of T6 heat treatment on A356 and A380 aluminium alloys manufactured by thixoforging combined with low superheat casting

The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.

Effects of heat treatment on microstructure and mechanical properties of ZA27 alloy

The effects of heat treatment on the microstructure and mechanical properties of ZA27 alloy were studied by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and mechanical characterization.The results indicated that the as-cast microstructure of the alloy was mainly composed of α,decomposed β,η and ε phases.After solid solution treatment at 365 ℃ for 1 h,α and η phases dissolved,and the microstructure of specimen was mainly composed of the supersaturated β phases.The phase decomposition of supersaturated ZA27 alloy is a two-stage phase transformation：the decomposition of the supersaturated β phase at the early stage of aging,and with the increase of aging time,ε phase decomposition through a four-phase transformation：α＋ε→T ＇＋ η.A good combination of high tensile elongation and reasonable strength can be achieved by suitable heat treatments.

Effect of heat treatment on microstructure and mechanical property of extruded 7090/SiC_p composite

The ultra high strength SiC particles （SiCp） reinforced Al-10%Zn-3.6%Mg-1.8%Cu-0.36%Zr-0.15% Ni composite was prepared by spray co-deposition. Microstructures of the extruded and different heat-treated bars were analyzed by transmission electron microscopy （TEM） and energy dispersive spectrometry （EDS）. Grain size of the composites prepared by two-stage solution is smaller than that by single-stage solution. After single-stage solution aging treatment, fine precipitates of both η and AlZnMgCu-rich phase can be found both intragranularly and intergranularly. While after the two-stage solution, an amorphous Si-Cu-Al-O （5 nm） layer appears at the interface. The addition of Ni and Zr modified the influence of the two-stage solution and inhibited the growth of the 7090/SiCp composite grain size. Heat treatments can significantly improve the fracture toughness of the composite. The fracture toughness first decreases then increases with the elongation of the aging time.

Synthesis of nano-to micrometer-sized B_(4)C particle-reinforced aluminum matrix composites via powder metallurgy and subsequent heat treatment

B4C/6061Al composites reinforced with nano-to micrometer-sized B4C particles were fabricated via powder metallurgy route consisting of spark plasma sintering(SPS)and hot extrusion and rolling(HER),followed by T6 treatment.The microstructural evolution and mechanical properties were investigated.Results showed that the status of B4C particles changed from a network after SPS to a dispersion distribution after HER.The substructured grains reached 66.5%owing to the pinning effect of nano-sized B4C,and the grain size was refined from 3.12μm to 1.56μm after HER.After T6 treatment,dispersed Mg_(2)Si precipitated phases formed,and the grain size increased to 1.87μm.Fine recrystallized grains around micro-sized B4C were smaller than those in the areas with uniform distribution of nano-sized B4C and Mg_(2)Si.The stress distributions of as-rolled and heated composites were similar,considering that the T6 heat treatment was only effective in eliminating the first internal stress.The Vickers,microhardness,and tensile strength of as-SPSed composites were greatly improved from HV 55.45,0.86 GPa,and 180 MPa to HV 77.51,1.08 GPa,and 310 MPa,respectively.Despite the precipitation strengthening,the corresponding values of as-heated composites decreased to HV 70.82,0.85 GPa,and 230 MPa owing to grain coarsening.

T6热处理对2618铝合金组织与力学性能的影响

文章研究了T6热处理对锻造成形后2618铝合金零件的组织和力学性能的影响。利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)、电子万能试验机对2618铝合金的显微组织和力学性能进行了测试,确定了该合金的最佳热处理工艺。结果表明,2618铝合金的最佳固溶处理工艺为525℃/1 h;最佳时效处理工艺为195℃/19 h。2618铝合金经过时效处理后,分布在晶界附近的低熔点S相(Al 2CuMg)完全回溶至基体,材料固溶强化效果显著。经过测试,其抗拉强度、屈服强度及断后延伸率分别达到459 MPa、379 MPa、9.3%。

Microstructures and mechanical properties of as-extruded and heat treated Mg-6Zn-1Mn-4Sn-1.5Nd alloy

The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy（OM）, X-ray diffractometer（XRD）, scanning electron microscopy（SEM）, electron back scattered diffraction（EBSD）, transmission electron microscopy（TEM）, hardness tests and uniaxial tensile tests. The results showed that the as-cast alloy consisted of α（Mg）, Mn, Mg7Zn3, Mg2 Sn and Mg Sn Nd phases. Dynamic recrystallization has completed during the extrusion process and the average grain size was 7.2 μm. After T5 treatment, the strength increased obviously, the yield strength and ultimate tensile strength of as-extruded alloy were increased by 94 and 34 MPa, respectively. Microstructure characterization revealed that the improvement of strength was determined by the high number density of β′1 rods.

Effect of pouring and cooling temperatures on microstructures and mechanical properties of as-cast and T6 treated A356 alloy

The A356 castings were fabricated using a well-developed temperature controlled permanent mold.To improve the strength and hardness of cast A356,the microstructures and mechanical properties of as-cast and T6 heat treated A356 alloy with various mold and pouring temperatures were studied.The results reveal that the undercooling is closely related to the mold and pouring temperatures.As the mold/pouring temperature changed from 258°C/680°C and 270°C/680°C to 288°C/650°C,the in-situ undercooling is 12°C,17°C and 11°C,respectively.It is observed that the Si phase changes from long continuous flake to discontinuous globular-fibrous morphology after T6 heat treatment as the mold and pouring temperature is 270°C/680°C,and the T6 heat treated specimens exhibit better mechanical properties in comparison to those as-cast ones with an increase of 162%and 102%in yield strength and elongation,which are 34.6%and 190%higher than the ASTM B108-03 a standard,respectively.As a result,the tensile fracture morphology of the as-cast A356 alloy shows quasi-cleavage fracture and the T6 heat treated A356 alloy shows ductile fracture.

一种新型三代含锇镍基单晶高温合金的析出相演化规律

铼和钌在镍基单晶高温合金中的应用常受限于其含量和相稳定性,寻找能同时代替铼和钌的新元素具有重要意义。本研究设计了一种具有高含量锇的新型镍基单晶高温合金,采用传统Bridgman技术制备铸态单晶合金,并对合金进行固溶时效处理,通过光学显微镜和扫描电子显微镜研究合金的析出相演化规律。结果表明:铸态合金中锇和钨偏析于枝晶干区域,而铝、钽、钛则偏析于枝晶间区域,即使经过长时间的固溶热处理,锇和钨仍有轻微的偏析。由于枝晶区域的元素偏析,一次时效处理后枝晶间的γ′相比枝晶干的γ′相更易转变为立方形,二次时效处理使析出相的尺寸和体积分数略微增大,形状从立方形向圆形转变。

固溶时效对6061铝合金焊接接头组织和性能的影响

采用脉冲钨极氩弧焊工艺对6 mm厚的6061-T6铝合金板进行焊接试验,对焊态接头和焊后进行530℃×6 h固溶+180℃×3 h人工时效处理的接头组织及性能进行分析。结果表明,焊态接头热影响区的强度显著降低,显微硬度最低为48 HV;固溶时效处理可强化焊接接头,热影响区显微硬度达到80 HV以上。拉伸断口形貌均为韧性断裂特征,与焊态接头相比,固溶时效处理后接头断口的韧窝要浅且细小,塑性变差。固溶时效处理改善了接头热影响区强化相的组织形态,由平衡相β-Mg 2Si转变成与基体保持共格或半共格的β″相或β′相,使其机械性能得以恢复。

Influence of Cu content on microstructure and mechanical properties of thixoformed Al-Si-Cu-Mg alloys

The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.

Effects of minor Y,Zr and Er addition on microstructure and properties of Al-5Cu-0.4Mn alloy

The effect of different contents of Y, Zr and Er on microstructure and properties of Al-5 Cu-0.4 Mn alloy was investigated. T6 heat treatment, OM, SEM and EDS methods were applied to the alloy. The results showed that fluidity and elongation of alloy adding Y, Zr and Er were improved, while with the increase of addition amounts, θ phase increased and grains were trended to grow up gradually. The Al-5 Cu-0.4 Mn alloy presented the maxed style of ductile and brittle fracture. After T6 heat treatment, the precipitation amounts of θ phase decreased dramatically and tensile strength and hardness significantly increased. Especially when addition contents were among 0.1-0.3 wt.%, tensile strength and hardness of heat-treated alloy increased greatly, almost doubled as that of the as-cast state. The tensile strength reached its maximum of 378.43 MPa when the addition amount was 0.3 wt.%. With the further increase of addition amounts, the elongation deteriorated and the proportion of ductile fracture reduced due to the limited dispersion strengthening effect of θ phase and Al_8Cu_4 Er. It demonstrated that addition of 0.1-0.3 wt.% Y, Zr and Er would generate positive effects and influences on Al-5 Cu-0.4 Mn alloy, which is significant for optimizing components and improving properties of Al-5 Cu-0.4 Mn alloy.

铝合金T6固溶时效热处理生产线

本文介绍了用于汽车发动机缸盖及缸体的铝合金T6固溶时效热处理生产线,该生产线能够满足铝合金大批量不间断的生产,生产线采用双层托辊驱动,淬火方式使用空气作为淬火介质,生产线已成功用于汽车发动机缸盖的T6固溶时效热处理,本生产线已为公司取得多项专利技术。

Microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

Effects of Zr additions on structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%) alloy

The effects of different Zr additions(0.05wt.%-0.5wt.%)on the structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%)alloy solidified under a high cooling rate(18℃·s^(-1)),in as-cast and T6 heat-treated conditions were studied.The as-cast structure of the alloy consists of equiaxed grains ofα-Al with an average size of 64μm which is unaffected by the Zr additions,indicating the ineffectiveness of Zr in the grain refinement of the alloy.Scanning electron microscopy,along with X-ray diffraction analysis revealed the presence of elongatedθ-Al2Cu at the grain boundaries;in addition,coarse Al3Zr particles exist in the intergranular regions of the 0.5wt.%Zr-containing alloy.After the T6 heat treatment,the elongatedθparticles were fragmented;however,the coarse Al3Zr particles remained unchanged in the microstructure.Also,the formation of fineβ’-Al3Zr andθ’’-Al3Cu/θ’-Al2Cu phases during T6 heat treatment was revealed by transmission electron microscopy.The results of the tensile tests showed that the Zr additions increase the strength of the alloy in both as-cast and T6 heat-treated conditions,but reduce its elongation,especially with 0.5wt.%Zr addition.The 0.3wt.%Zr-added alloy in the T6 heat-treated condition has the highest quality index value(249 MPa).Fractography of the fracture surfaces of the alloys revealed ductile fracture mode including dimples and cracked intermetallic phases in both conditions.

汽车用6061-T6板材高强度高延伸率工艺研究

为满足汽车轻量化的性能要求,通过对汽车用6061-T6薄板中主要合金元素Si、Mg含量的优化,试验了4种不同主合金元素配比方案。在气垫式热处理炉内快速加热、保温及固溶的条件下,获得最佳的MgSi溶解度,并通过时效工艺探索,确定在最佳固溶条件下4种方案的力学性能变化趋势。结合电子显微镜OM和扫描电镜SEM对时效样品进行观察,发现Si含量在0.7%、Mg含量在0.9%左右的配比方案下,其时效组织中存在过剩Si。进一步对时效析出的强化相Mg_(2)Si质点进行细化,可以获得高强度组织。研究表明,采用这种成分方案,在最佳的固溶及时效工艺条件下,可实现力学性能抗拉强度≥320 MPa,屈服强度≥290 MPa,延伸率≥13.5%的高强高延伸的指标要求。

紧固件用TB2钛合金棒材热处理工艺研究

研究了热处理工艺对原始组织为粗大β晶粒+少量细小α晶粒的紧固件用TB2钛合金棒材组织与力学性能的影响。结果表明:随着固溶温度的升高,棒材组织中α相含量逐渐减少,β晶粒尺寸明显增大,经780℃固溶后强度和塑性匹配最好;固溶+时效处理时,随着时效温度的升高,棒材组织中析出的次生α相体积分数先增加后减少,且棒材强度先升高后降低;经固溶+预拉伸变形+时效处理后,棒材组织中晶粒有一定细化,次生片状α相含量增多,抗拉强度较固溶后直接时效提高了近10%。

以多阶段和非等温为特征的新型铝合金热处理方法综述

预备热处理和最终热处理在铝合金产品的生产制备中都发挥着不可替代的作用。合金成分的均匀程度、弥散相的尺寸及其与基体的共格关系、再结晶晶粒的大小和长径比、溶质元素的过饱和度和时效沉淀相的特征等都直接决定了材料的力学性能、耐腐蚀性能和可加工性。在工程应用中,由于产品尺寸的影响,涉及加热和/或冷却过程的非等温现象是不可避免的。因此,具有工程适用性的新型热处理技术是固态相变理论得以实现的必要延伸。本文以AlZnMg(Cu)、AlMgSi和AlCu(Li)等典型变形铝合金为研究对象,综述了其均匀化、固溶和时效技术的研究现状,重点归纳和总结了新型热处理技术的多阶段热处理和非等温热处理。

高强高弹导电C70250铜合金工艺研究

本文简述了C70250铜合金材料的背景及发展现状,根据后续加工对材料特性和具体性能的要求,重点阐述了C70250铜合金带材的合金特性、熔炼铸造、热轧在线淬火、连续在线固溶、时效析出处理等工艺技术,研究不同在线固溶、热处理、冷变形与时效工艺及不同工序组合和性能遗传性对C70250合金的晶粒尺寸、析出相粒子尺寸及分布规律,同时对合金的力学与电学性能进行测试。结果表明,半连续生产C70250铜合金经过时效+冷轧+在线固溶处理+冷变形+时效处理相组合的形变热处理时效工艺后,合金组织晶粒0.015μm细小均匀,析出相分布更加弥散,其具有抗拉强度为692MPa,屈服强度为651MPa,伸长率为10%,导电率为45.62%IACS,折弯性能优良的综合性能;能够很好的满足集成电路和连接器对高强高弹导电材料的要求。