热处理工艺对15CrMoR钢带状组织和冲击性能的影响

利用光学显微镜、扫描电镜和冲击试验机等仪器研究了15CrMoR钢中带状组织在热处理过程中的演变及其对冲击性能的影响。结果表明:奥氏体化后缓冷会出现铁素体-珠光体带状组织, 快冷则可以抑制带状组织的出现,但快冷会导致粒状贝氏体等非平衡组织形成。粒状贝氏体组织中的贝氏体铁素体基体和马氏体-奥氏体岛在回火过程中逐渐沿Cr、Mo等碳化物形成元素偏聚的区域分解出碳化物,形成富碳化物带,降低钢的横向冲击性能。15CrMoR钢加热到1100 ℃并保温7 h后可消除带状组织,改善钢的横向冲击性能。     

带状组织对铝/镁异种金属搅拌摩擦焊接头力学性能的影响

采用搅拌摩擦焊(FSW)对厚度为4 mm的6061铝合金与AZ31B镁合金进行不同工艺的平板对接试验. 采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及能谱仪(EDS)对接头进行微观组织观察,采用电子万能试验机对接头力学性能进行测试. 结果表明,在接头焊核区(WNZ)中存在着明显的带状组织,带状组织是由插入镁基体中的铝合金条以及弥散分布在条带上的金属间化合物(IMCs)组成;IMCs主要为Al₁₂Mg₁₇和Al₃Mg₂;铝/镁异种金属FSW接头裂纹形核和扩展均发生在带状组织内;焊接工艺影响带状组织形态和IMCs尺寸及数量;随着转速(n)的增加或焊接速度(v)的降低,带状组织呈弯曲状,长度相对较短且呈不连续分布;当转速(n)过高或焊接速度(v)过低时,带状组织变细,但IMCs数量增多且尺寸变大;铝/镁异种金属FSW接头强度主要取决于带状组织形态和IMCs尺寸及数量.     

晶粒细化对Fe-Ni-Mo-Cr系马氏体时效钢组织和性能的影响

采用显微组织观察和力学性能测试,研究了晶粒细化处理对Fe-Ni-Mo-Cr系马氏体时效钢组织和性能的影响.结果表明,等温循环相变可使晶粒平均尺寸达到8～10 μm;同时使合金的马氏体板条碎化,亚结构和析出相形核位置增多,逆转变奥氏体长大速度加快.循环细化后的时效合金中调幅组织更为明显,棒状的Ni3Mo、Ni3Ti及逆转变奥氏体的弥散度也比未经过循环细化处理的要大,合金的强度和塑性明显改善.     

热处理工艺对挖掘机铲斗用钢组织和力学性能的影响

利用热膨胀仪、拉伸试验机、金相显微镜以及扫描电镜对挖掘机铲斗用钢的相变点、力学性能和微观组织进行了研究,分析了热处理工艺对力学性能的影响。结果表明,挖掘机铲斗用钢在10℃/s的加热速度下,其Ac1和Ac3分别为776℃和832℃;屈服强度在700 MPa以上,抗拉强度在900 MPa以上,伸长率在13%以上;微观组织为回火索氏体,细小弥散的碳化物分布其上。热处理第一次正火温度在820~860℃之间,第二次正火温度在850℃附近为宜,在450~550℃区间回火都有比较好的力学性能,回火时间不宜小于6 h。     

热输入对800 MPa级钢接头组织及性能的影响

系统研究了焊接热输入对新一代800MPa级高强度结构钢(RPC钢)焊接接头组织及力学性能的影响。研究结果表明，采用最新研制的超低碳贝氏体焊丝焊接800MPa级RPC钢获得了强韧性匹配良好的焊接接头；焊缝一次柱状品的宽度随热输入的增加而增大，焊缝金属二次组织中基本上消除了先共析铁素体和侧板条铁素体，组成焊缝的基本类型为板条贝氏体、针状铁素体和粒状贝氏体；随着热输入的增大，焊接接头的抗拉强度逐渐降低，而低温冲击韧度则先升高，然后又下降；在热输入为20kJ／cm时焊缝金属低温韧性出现峰值与焊缝获得细小密集的针状铁素体组织有关。     

热处理工艺对TCS不锈钢力学性能的影响

采用微机控温的箱式电阻炉,对TCS不锈钢进行了热处理实验,并对其力学性能和组织进行了观察和测试。结果表明:热处理温度低于900℃时,加热温度和保温时间对其性能影响不大。热处理温度高于900℃时,随着加热温度的升高,抗拉强度和硬度先是急剧增大,然后有降低的趋势,最大值分别为:870MPa和266HB,转折温度点在1200℃左右;而冲击功和伸长率则随着加热温度的延长而降低。当温度高于900℃时,TCS不锈钢发生铁素体—奥氏体转变,奥氏体在淬火过程中析出马氏体;随着温度的升高,高于1200℃时,淬火组织中含有大量的高温铁素体。     

热处理对G50超高强度钢力学性能的影响

通过调整热处理过程的主要工艺参数,研究了840～900℃淬火以及200～500℃回火温度范围内G50钢硬度、强度、塑性以及冲击性能的演变规律。结果表明:在相同回火温度下,随着淬火温度的升高,G50钢的硬度和强度总体呈降低趋势,而塑性和冲击性能则得到提高;在相同淬火温度下,随着回火温度的升高,G50钢的硬度、强度和冲击性能在总体上呈降低趋势,而塑性则先降低后增加。"高温淬火+低温回火"将有助于G50钢获取较优的力学性能。      

时效时间对SLM 18Ni300马氏体时效钢组织性能的影响

对激光选区熔化(Selective laser melting,SLM)成形马氏体时效钢进行固溶及500℃时效不同时间的热处理,分析时效时间对其组织性能的影响.结果表明:SLM 18Ni300钢经固溶+时效处理后,其组织为马氏体、逆转变奥氏体和Ni3(Mo,Ti)析出相,随时效时间增加,析出相数量逐渐增加并聚集长大,同...     

时效温度对SLM 18Ni300马氏体时效钢显微组织和力学性能的影响

采用激光选区熔化(SLM)技术制备了18Ni300马氏体时效钢,结合拉伸试验、硬度测试和显微组织表征等手段,研究了时效温度(390, 490, 590℃)对SLM 18Ni300马氏体时效钢显微组织和力学性能的影响。结果表明,SLM成形试样主要由Fe-Ni马氏体基体和胞状亚结构组成,经时效处理后,试样微观组织发生显著变化。随着时效温度的升高,胞状亚结构逐渐分解,马氏体逆转变成为奥氏体,Σ3晶界占比下降。同时,Ni₃X(X=Ti, Al, Mo)纳米相弥散析出,并在590℃时粗化。随着时效温度的升高,SLM 18Ni300马氏体时效钢的强度和硬度均先增加后下降,伸长率先降低后增加。其中,490℃时效的SLM马氏体时效钢兼具超高强度和较好塑性,这与其基体中弥散分布的纳米析出相、适量的奥氏体含量和较低的Σ3晶界占比有关。     

Influence of nonmetallic inclusion characteristics on the mechanical properties of rail steel

An extensive investigation has been carried out on six commercial heats of pearlitic rail steel to study the influence of nonmetallic inclusion characteristics on the tensile, fatigue, and fracture toughness properties. The steels investigated were made through the basic oxygen furnace (BOF)-continuous casting route and rolled in the rail and structural mill into 90 kg/mm² ultimate tensile strength (UTS) grade rails. While tensile properties (yield strength [YS], UTS, and elongation) of the rail steels investigated were found to be insensitive to inclusion type and volume fraction at their present level (0.23 to 0.45%), the fracture toughness and high-cycle fatigue properties were found to be inclusion sensitive. The fracture toughness values of the steels were found to range between 42.33 and 49.88 MPa √m; higher values, in general, were obtained in heats exhibiting lower volume fractions (0.15 to 0.19%) of sulfide inclusions. The high-cycle fatigue limit, i.e., stress corresponding to 10⁷ cycles, was found to be higher in cleaner steels, particularly in those with lower volume fractions of oxide inclusions. This phenomenon was corroborated by scanning electron microscopy (SEM) observations of fracture surfaces, where oxide inclusions in particular were found to be instrumental in crack initiation. Although fatigue life did not show any direct correlation with the volume fraction of sulfides, elongated MnS inclusions were sometimes observed at crack initiation sites of fatigue-tested specimens.     

Influence of Mo content on microstructure and mechanical properties of β-containing TiAl alloy

The influence of Mo content on the microstructure and mechanical properties of the Ti-45Al-5Nb-xMo-0.3Y (x=0.6, 0.8, 1.0, 1.2) alloys was studied using small ingots produced by non-consumable electrode argon arc melting. The results show that small quantities of β phase are distributed along γ/α₂ lamellar colony boundaries as discontinuous network in the TiAl alloys owing to the segregation of Mo element. The γ phase forms in the interdentritic microsegregation area when the Mo addition exceeds 0.8%. The β and γ phases can be eliminated effectively by subsequent homogenization heat treatment at the temperature above T_α. The evolution of the strength, microhardness and ductility at different Mo contents under as-cast and as-homogenization treated conditions was analyzed, indicating that excessive Mo addition is prone to cause the microsegregation, thus decreasing the strength and microhardness obviously, which can be improved effectively by subsequent homogenization heat treatment.     

热处理工艺对35CrMo钢组织及性能的影响

利用SEM、金相显微镜、冲击试验机研究了淬火+回火、贝氏体等温淬火两种热处理工艺对35CrMo钢组织及性能的影响。结果表明,随回火温度提高或贝氏体含量的增加,材料的强度降低、塑韧性增加;回火索氏体组织的冲击断口表现为塑性韧窝状,而贝氏体/马氏体复相组织的冲击断口的纤维区表现为塑性韧窝状,放射区表现为脆性解理断裂;在等强度、塑韧性条件下,回火索氏体裂纹形成功低于贝氏体/马氏体复相组织,当裂纹形成后,回火索氏体组织裂纹扩展功高于贝氏体/马氏体复相组织。     

两相区冷速对齿轮钢20CrMnTi带状组织的影响

带状组织包括一次带状组织和二次带状组织,是20CrMnTi等亚共析钢常见的组织缺陷,使产品的力学性能显著降低。一次带状组织产生的根本原因是枝晶偏析,通过控制连铸水冷可以抑制该带状组织的产生。通过钢的模拟冷却试验,研究了齿轮钢20CrMnTi二次带状组织的变化规律,根据铁碳相图和亚共析钢的连续冷却曲线,提出了两相区(F+A)快冷可以避免二次带状组织(通常所称的带状组织)出现的理论。     

预处理对低温用高强度钢00Cr12Ni10MoTi力学性能的影响

研究了预处理对低温用高强度不锈钢00Cr12Ni10MoTi力学性能的影响.结果表明,经过750℃预处理和750℃最终固溶处理后发生两次非扩散α’→γ相变,此时奥氏体经过两次相变硬化,位错密度明显提高,强度显著增加,同时预处理形成了稳定的马氏体/奥氏体复相组织改善了低温韧性;预处理温度低于750℃、尤其是低于As点会使750℃固溶处理的最终残留奥氏体逆转变量显著增加,低温韧性进一步提高,但钢的强度明显降低.     

Influence of heat treatment on the microstructure and mechanical properties of DZ951 alloy

DZ951 directionally solidified nickel-base superalloy is mainly strengthened by y phase.Regularly aligned cuboidal and bimodal γ precipitates were attained by two heat treatments.The effect of microstructure on the mechanical properties of DZ951 alloy has been investigated.The results indicate that MC carbide changes to little blocks during aging treatment at 1050℃ (HT1).MC carbide partly degrades into M23c6 and there is a layer of γ around the carbide during aging treatment at 115℃ (HT2),which is beneficial to the elongation of DZ951 alloy.Small γ volume fraction and the uneven deformation structure are contributed to low mechanical propexties of the as-cast alloy.HT1 alloy has a better stress rupture life at 1100℃50 MPa and yield stress at 20℃,800℃ and 1100℃,which is attributed to regularly aligned cuboidal γ phase and even deformation structure.HT2 alloy has a good combination of strength and ductility.This arises fi'om the bimodal γ precitates and the degeneration of MC carbide.     

Influence of Ce on microstructure and mechanical properties of LA141 alloys

LA141-（0-1.2）Ce alloys were prepared with vacuum induction melting method. The effects of Ce addition on the microstructure and mechanical properties of LA 141 alloys were studied. The microstructure and phases composition of these alloys were analyzed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry. The mechanical properties of these alloys were measured with tensile tester. The results show that Ce has refining effect on the alloys. In the alloys, some Al2Ce compounds exist, which make the A1 content dissolved in a and β phases decrease and the hard brittle Mg17Al12 phase refined. The refining effect improves the mechanical properties of alloys. When Ce content is 0.9%（mass fraction）, the tensile strength reaches 206.8 MPa and the elongation is two times as high as that of LAl41 alloy. Due to the generation of Al2Ce, the content of Al solid soluted in β phase decreases resulting in the decrease of alloy hardness with the addition of Ce.     

30CrMo锯片用钢带状偏析及其改善措施

通过试验分析了齿根部裂纹失效的30CrMo激光焊接锯片基体,阐明了30CrMo中的带状偏析是引起锯片基体金相组织中出现异常白亮条带状组织的主要原因;针对其对锯片基体疲劳寿命的影响,提出并验证了通过正火预处理和延长保温时间的热处理工艺来减轻偏析危害的可行性。     

热处理对0Cr13钢力学性能和磁性能的影响

研究了不同再结晶退火和调质处理工艺对0Cr13不锈钢常温下力学性能和磁性能的影响。结果表明:0Cr13钢经980 ℃×1 h 淬火,水冷+725 ℃×2 h回火,水冷+400 ℃×2 h回火,炉冷处理,可以获得铁素体和马氏体双相组织,力学性能与磁性能的匹配较好;0Cr13钢经980 ℃×1 h淬火,水冷+725 ℃×2 h回火,水冷+870 ℃×2 h回火,炉冷处理,磁性能优异,且矫顽力较小,但强度显著下降。820 ℃×5 h 炉冷再结晶退火后,可获得更加规整、均匀的等轴铁素体组织,强度比调质处理的低,但具有良好的软磁性能。调质处理后采用870 ℃高温回火,可以显著降低材料的矫顽力H_c和剩余磁感应强度B_r,去磁场时可快速退磁。0Cr13钢中铁素体量多则弱磁特性好,马氏体量多则强度高,磁性能和强度存在一定的矛盾关系,较好的磁性能会损失一定的强度,反之亦然。     

热处理对42CrMoNi钢轴承套圈力学性能的影响

针对42CrMoNi钢轴承套圈调质后出现的低温冲击韧性不足问题进行分析,优化了调质热处理工艺并对采用优化工艺前后的轴承套圈力学性能进行了对比。结果表明,采用优化后的热处理工艺即淬火温度保持950 ℃,预冷3 min后油冷淬火,565 ℃一次回火+550 ℃二次回火的二次回火快速油冷工艺可提高42CrMoNi钢轴承套圈调质处理后的低温冲击韧性,使其综合力学性能良好,满足技术要求。     

Effect of grain refinement on phase transformation behavior and mechanical properties of Cu-based alloy

A small amount of misch metal was added to Cu-Zn-Al alloy in order to study its effect on grain refinement, mechanical properties, phase transformation behavior and stabilization of martensite. It is found that the addition of misch metal is very effective for reducing the grain size. The coarse grains over 1 000 μm are refined to the size of 30 μm by the addition of 0.43% (mass fraction) misch metal. The grain size of thermo-mechanically treated alloys is barely affected by cold working. The fracture strength and ductility increase significantly with the increase of misch metal content when tensile test is carried out below M_f temperature. Also, the fracture strength is larger in the case of post-quench ageing treatment than that in the case of direct quench ageing treatment. The fracture mode is changed from transgranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal.