异步热轧对钛合金Ti-6Al-4V微观组织及力学性能的影响（英文）

通过异步/同步热轧实验研究了异步热轧工艺对钛合金显微组织和力学性能的影响。实验表征了试样的显微组织、力学性能、断口形貌和微观取向。结果表明,复杂应变路径较之简单应变路径能更好地细化晶粒,同时提高强度和塑性,并且表层晶粒小于中心晶粒。异步轧制工艺相比同步轧制能更好地获得细小晶粒。异步轧制试样的强度及塑性值高于同步轧制试样相应值,提高异步速比可提高强度及塑性值。异步轧制试样的塑性变形机制可能是滑移,而同步轧制试样塑性变形机制为滑移或孪晶。     

异步热轧对压力容器钢组织及力学性能的影响

对比研究了异步热轧对压力容器钢组织和力学性能的影响。结果表明:异步轧制材料的晶粒尺寸由表层至中心逐渐增大,表层晶粒达到1 mm;常规轧制沿厚度晶粒尺寸差别较小;常规轧制冲击试样断裂由脆性与韧性构成,而异步轧制试样断裂为韧性;异步轧制的强度及塑性优于常规轧制。     

轧制路径对非对称压下量轧制AZ31镁合金显微组织和性能的影响（英文）

对AZ31镁合金进行4种不同路径的非对称压下量轧制,研究其对材料显微组织演化和力学性能的影响。路径A为连续轧制,路径B和C在轧制时轧板分别沿轧向和法向旋转180°,路径D为单向轧制。采用有限元法分析轧板的应变状态,并通过金相显微镜、X射线衍射和电子背散射衍射技术观察分析板材的显微组织和织构特征,另外利用拉伸试验测试材料的力学性能。结果表明,路径D轧制时所产生的等效应变值最大;与其他试样相比,试样D的组织较均匀,由细小的晶粒组成,且其基面织构较弱并发生了一定倾转;因此,试样D表现出较优异的力学性能,这表明路径D能够有效地提高AZ31板材的强度和塑性。     

边部组织状态对低碳热轧酸洗板冲压成形的影响

针对低碳热轧酸洗板边部材料冲压时易出现制耳、开裂现象,对钢板边部显微组织和成形性能进行了研究分析.钢板边部显微组织呈现明显的晶粒粗大及混晶特征.钢板边部的力学性能和中部位置相比,强度略低,成形性能恶化,钢板边部纵向和横向的塑性应变比r值显著低于中部,只有0.31和0.65,各向异性明显.钢板边部的显微组织和力学性能特征是由于边部实际轧制温度低,处于先共析铁素体和奥氏体两相区轧制形成的.低碳热轧酸洗板边部的显微组织和力学性能特征差异是导致材料在冲压时出现较多的制耳和开裂缺陷的原因.通过产品热轧工艺改进、成分调整可以改善热轧酸洗板边部组织和性能状态.     

异步轧制AZ31镁合金板材的孪晶组织及织构北大核心CSCD

采用异步轧制（AR）工艺和同步轧制（NR）工艺制备了AZ31镁合金板材,分析了AZ31镁合金板材的组织性能和力学性能,研究了轧制过程中孪晶组织和织构的演变规律,以及异步轧制工艺参数对镁合金板材组织、织构和力学性能的影响。结果表明,在压下量为3％～15％的范围内,异步轧制与同步轧制板材在晶粒尺寸以及均匀性上有相似的变化趋势。在变形初期,随压下量的增加,孪晶数量不断增加,孪晶使异步轧制与同步轧制板材中晶粒取向都发生偏转,即C轴趋向于垂直于法向（ND）,从而使初始挤压板材的丝织构强度减弱;当压下量达到24％时孪晶大量减少或消失。在压下量为3％～24％的范围内,同步轧制对板材力学性能的影响并不明显,峰值应变呈交替性变化,异步轧制板材在压下量达到24％时,表现出了良好的塑性变形能力,抗拉强度达到309MPa,峰值应变达到16．3％。     

轧制路径对AZ31镁合金薄板组织性能的影响

研究了异步轧制路径对AZ31镁合金板材的金相组织和性能的影响。结果表明,以每道次轧制方向旋转180°而板正法向不变的路径轧制时,板材的金相显微组织较好,晶粒细小（约为20μm）,孪晶少,伸长率达到26%,并且板材的屈服强度、应变硬化指数较高;而按每道次板材轧制方向和板正法向均旋转180°的路径轧制时,板材的塑性应变比值最大。这说明异步轧制路径对AZ31镁合金性能的影响是比较复杂的,应该综合考虑异步轧制工艺条件的影响,通过工艺优化提高异步轧制AZ31镁合金板材的冲压成形能力。     

异步轧制对Mg_(98.5)Zn_(0.5)Y_1合金晶粒和力学性能的影响

试验研究了异步轧制工艺参数对Mg_(98.5)Zn_(0.5)Y_1合金力学性能的影响,探讨了异步轧制工艺参数对合金晶粒细化及其强化机制的影响。结果表明:随着轧制道次的增加,材料的屈服强度和抗拉强度增加,最高可达到325 MPa;异步轧制产生的剪切应变能有效促进压缩孪晶和晶粒内部及晶粒间的相互作用,产生动态再结晶,从而导致大晶粒的内部转变为许多小亚晶,达到细化晶粒,提高镁合金力学性能的目的。     

同步和异步轧制AZ31镁合金板材的织构及力学性能

采用同步轧制(NR)和异步轧制(AR)工艺对AZ31镁合金挤压板材进行了轧制,研究了轧制过程中组织和织构的演化,以及总压下量和异步比对轧材组织、织构和力学性能的影响。结果表明,在压下量为3%～15%的范围内,同步轧制与异步轧制板材在晶粒尺寸以及均匀性上有相似的变化趋势。轧制过程中,在变形初期,随压下量的增加,孪晶数量不断增加,孪晶使同步轧制与异步轧制板材中晶粒取向都发生偏转,即C轴趋向于垂直于法向(ND),从而使初始挤压板材的丝织构强度减弱;而当压下量达到24%时,孪晶大量减少或消失。在压下量为3%～24%的范围内,同步轧制对板材力学性能的影响并不明显,峰值应变呈交替变化;异步轧制板材在压下量达到24%左右时,表现出了良好的塑性变形能力,抗拉强度达到309MPa,峰值应变达到0.163。     

初始取向对大应变轧制AZ31镁合金板材显微组织和力学性能的影响

采用大应变轧制技术对轧制面与挤压板材ED-TE面分别成90°、45°和0°的AZ31镁合金板材进行加工,研究初始取向对板材显微组织和力学性能的影响。结果表明:孪生诱发动态再结晶是大应变轧制过程中主要的再结晶机制,动态再结晶的发生使合金晶粒细化、力学性能大幅提高。轧制过程中孪生与板材初始取向密切相关,通过改变初始取向可控制板材晶粒细化和强度改善效果。0°轧制试样大应变轧制过程中,大部分晶粒的c轴受压,基面滑移启动难度增加,孪生的作用增强,压缩孪晶密度增大,进而通过孪生诱发动态再结晶获得更为细小的再结晶组织和更为优异的力学性能。压下量为80%时,0°轧制板材的平均晶粒尺寸为5μm,抗拉强度、屈服强度和伸长率分别为311.4 MPa、202.6 MPa和26.9%。     

轧制工艺对铸轧AZ31镁合金板材组织的影响

观察了铸轧AZ31镁合金板材经不同异步比轧后试样的显微组织。结果表明,与同步轧制相比,异步轧制能显著降低AZ31镁合金的动态再结晶温度,细化晶粒,并且提高其低温轧制时的成形能力,无需中间退火处理即可制备出最终厚度为0.7 mm的镁合金薄板。同时,异步轧制能够明显减弱板材的基面织构,但其强度并不随异步比增加呈现明显的单调递减规律。     

Microstructure,Mechanical Properties and Texture Evolution of Mg-Al-Zn-La-Gd-Y Magnesium Alloy by Hot Extrusion and Multi-Pass Rolling

A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86Y (wt%) alloy was developed by hot extrusion and multi-rolling processes. Relationships between microstructure, mechanical properties and texture evolution of the extruded and rolled alloy were investigated. The rolling process had significant effect on grain refinement of the extruded plate. The grain size reduced from 12.3 to 4.9 μm with the increasing rolling pass. With the increase in rolling pass, the proportion of dynamic recrystallized (DRXed) grains increases due to particle-stimulated nucleation, grain boundary nucleation and twin induced nucleation. In the process of multiple rolling, the basal pole gradually tilted from normal direction to transverse direction due to the asymmetric deformation and irregular grain deformation, resulting in the weakening of the base texture. The results showed that grain refinement and texture weakening were the main reasons for the good ductility of the alloy.     

铁素体轧制对普通用冷轧钢板组织和性能的影响

采用光学显微镜和扫描电镜对比研究了铁素体区热轧工艺及奥氏体区热轧工艺对普通用冷轧钢板(SPCC)产品热轧组织、冷轧组织及性能的影响。结果表明,与奥氏体区轧制工艺相比,采用铁素体区热轧工艺生产的SPCC热轧板晶粒尺寸会增大约17 μm,{111}面织构数量减少了8.74%,强度略微降低,而{001}<110>织构数量增加了12.40%,强度提高了19.81。此外,采用铁素体区热轧工艺生产的SPCC成品晶粒呈近似等轴状,与奥氏体区热轧工艺相比平均晶粒尺寸增大了4.5 μm。SPCC铁素体区轧制热轧板中更大的晶粒尺寸、更少的{111}面织构及更强的{001}<110>取向织构导致了冷轧成品更低的屈服强度和塑性应变比r值,较奥氏体区热轧工艺而言平均屈服强度降低了19 MPa,平均r值下降了1.1。     

冷却方式对Nb-Ti微合金钢组织和性能及沉淀行为的影响

两阶段控制轧制后,采用不同的冷却路径进行冷却,研究冷却路径对Nb-Ti微合金钢组织和性能及沉淀行为的影响.结果表明,超快冷+空冷冷却路径可获得细晶组织,晶粒平均尺寸约为7.76μm,屈服强度高达425 MPa,抗拉强度高达500 MPa.超快冷+炉冷试样中存在细小的沉淀粒子,沉淀粒子尺寸主要集中在2—7 nm,而超快冷+空冷试样中只存在少量球形沉淀粒子,轧后直接空冷可获得相间沉淀粒子.不同冷却路径获得的热轧板在700℃下退火300 s后,沉淀粒子发生明显的粗化;退火处理后,超快冷+炉冷试样的晶粒平均尺寸减小为6.47μm,相对于退火前,其屈服强度和抗拉强度分别增加50和30 MPa、强度的增加主要源于细晶强化.对于含0.03%Nb(质量分数)的Nb-Ti微合金钢,由于沉淀粒子的体积分数有限,因此细晶强化效果远高于沉淀强化效果,强度的变化与晶粒尺寸的变化具有很好的对应性.另外,加工硬化指数与晶粒尺寸密切相关.随着晶粒平均尺寸的增加使加工硬化指数增加.     

Influence of Hot Deformation on Mechanical Properties and Microstructure of a Twin-Roll Cast Aluminium Alloy EN AW-6082

Thin strips of medium- and high-strength age-hardening aluminium alloys are widely used in the automotive industry. Reducing their production costs caused by high energy consumption is an actual challenge. The implementation of the twin-roll casting technology is promising. However, mechanical properties of directly cast high-alloyed thin aluminium strips are oftentimes inadequate to standard specifications. In this work, the influence of a hot deformation following a twin-roll cast strip process on the mechanical properties and microstructure is investigated. For this study strips of age-hardening aluminium alloy EN AW-6082—manufactured at a laboratory scaled twin-roll caster—were single-pass rolled at temperatures of 420 °C and true strains of up to 0.5. The mechanical properties of the as-cast and by different strains hot deformed material in the soft-annealed and age-hardened states were characterized by tensile tests. The results reveal that the twin-roll cast material features the necessary strength properties, though it does not meet the standard requirements for ductility. Furthermore, the required minimum strain during hot rolling that is necessary to ascertain the standard specifications has been determined. Based on micrographs, the uniformity of the mechanical properties and of the microstructure as a result of recrystallization due to hot metal forming and heat treatment were determined. A fine-grain microstructure and satisfactory material ductility after prior rolling with a true strain above 0.41 for the age-hardened state T6 and above 0.1 for the soft-annealed state O have been established.     

冷却方式对Nb-Ti微合金钢组织和性能及沉淀行为的影响

两阶段控制轧制后,采用不同的冷却路径进行冷却,研究冷却路径对Nb-Ti微合金钢组织和性能及沉淀行为的影响.结果表明,超快冷+空冷冷却路径可获得细晶组织,晶粒平均尺寸约为7.76μm,屈服强度高达425 MPa,抗拉强度高达500 MPa.超快冷+炉冷试样中存在细小的沉淀粒子,沉淀粒子尺寸主要集中在2-7 nm,而超快冷+空冷试样中只存在少量球形沉淀粒子,轧后直接空冷可获得相间沉淀粒子.不同冷却路径获得的热轧板在700℃下退火300 s后,沉淀粒子发生明显的粗化;退火处理后,超快冷+炉冷试样的晶粒平均尺寸减小为6.47μm,相对于退火前,其屈服强度和抗拉强度分别增加50和30 MPa,强度的增加主要源于细晶强化.对于含0.03%Nb(质量分数)的Nb-Ti微合金钢,由于沉淀粒子的体积分数有限,因此细晶强化效果远高于沉淀强化效果,强度的变化与晶粒尺寸的变化具有很好的对应性.另外,加工硬化指数与晶粒尺寸密切相关,随着晶粒平均尺寸的增加使加工硬化指数增加.     

Microstructure and Mechanical Property of Hot-Rolled Mg-2Ag Alloy Prepared with Multi-pass Rolling

A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag alloy. The relationship between microstructure and mechanical property is investigated. The result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization (DRX) behavior of the rolled Mg-2Ag alloys. The DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass increases. The yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling pass. The elongation of rolled sample is gradually improved when the rolling pass increases from one to three, while a significant drop of elongation shows in the four-pass rolling sample. The strong basal texture, refined grains, high-density dislocations, and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys, while the low-density dislocations, homogeneously fine-grained microstructure, and weak texture are critical for improving the ductility.     

终轧工艺对AM50镁合金轧板力学性能和织构特征的影响

采用不同的轧辊温度和速率制备AM50镁合金轧板,研究终轧工艺对镁板力学性能和织构特征的影响。研究表明：在轧辊温度为200°C和轧辊速率为5 m/min条件下制备的镁板的强度（极限抗拉强度：295 MPa;屈服强度：224 MPa）和伸长率（22.9%）之间达到较优组合;在热轧过程中,轧板的屈服强度主要取决于轧制温度,而织构强度则对轧辊速率更为敏感;提高轧制温度或轧辊速率均可改善AM50镁合金板材力学性能的各性异性。     

短流程CSP和2250mm轧制生产50W600无取向硅钢组织及性能对比

针对短流程CSP和半连轧2250 mm两种不同热轧工艺所生产的50W600无取向硅钢,进行力学拉伸试验、显微组织观察及织构分析,研究两种工艺生产的无取向硅钢在组织状态和整体性能上的差异。结果表明:短流程CSP工艺生产的50W600无取向硅钢显微组织较为均匀,平均晶粒尺寸较2250 mm热轧工艺生产的粗大,热轧板力学性能略低。短流程CSP工艺生产的50W600无取向硅钢成品板酸轧、连续退火后不利织构相对较少,磁性能优于2250 mm热轧工艺生产的50W600钢。     

The effect of through-thickness strain distribution on the static recrystallization of hot rolled austenitic stainless steel strip

The accumulation of strain and the evolution of the microstructures at the surface and centre of thin hot rolled 304 austenitic stainless steel strips were studied by comparing their recrystallisation behaviour and recrystallised grain sizes. It appears that the evolution of microstructure can be predicated using a simple approach and that the accumulated strain depends only on the amount of strain, and not on the strain path (ie. the effect of strain reversal in the roll gap.) This was confirmed by the observation that the time for 50% recrystallisation and the recrystallised grain size were found to be approximately a log linear function of strain when the strain in the centre of the hot rolled strips was calculated from the rolling reduction and the strain in the surface region was estimated from the predicted ratio of surface strain to axial strain obtained from FE modelling using the commercial package ABAQUS.     

Effect of ageing on microstructure and mechanical properties of bulk, cryorolled, and room temperature rolled Al 7075 alloy

The effect of ageing on mechanical properties and microstructural characteristics of a precipitation hardenable Al 7075 alloy subjected to rolling at liquid nitrogen temperature and room temperature are has been investigated in the present work employing hardness measurements, tensile test, XRD, DSC, and TEM. The solution-treated bulk Al 7075 alloy was subjected to cryorolling and room temperature rolling to refine grain structures and subsequently ageing treatment to simultaneously improve the strength and ductility. The solution treatment combined with cryorolling up to a true rolling strain of 2.3 followed by low temperature ageing at 100 °C for 45 h has been found to be the optimum processing condition to obtain fine grained microstructure with improved tensile strength (642 MPa) and good tensile ductility (9.5%) in the Al 7075 alloy. The combined effect of suppression of dynamic recovery, partial grain refinement, partial recovery, solid solution strengthening, dislocation hardening, and precipitation hardening are responsible for the significant improvement strength-ductility combination in the cryorolled Al 7075 alloy subjected to peak ageing treatment. The cryorolled and room temperature rolled Al 7075 alloy, upon subjecting to peak ageing treatment, have shown higher strength and ductility in the former than the latter. It is due to presence of high density of nanosized precipitates in the peak aged cryorolled sample.