Improving the Mechanical Properties of Mg-Gd-Y-Ag-Zr Alloy via Pre-Strain and Two-Stage Ageing

In this study, we investigated the effects of single-stage ageing (SSA), two-stage ageing (TSA), 2% pre-strain + single-stage ageing (P2%SSA) and 2% pre-strain + two-stage ageing (P2%TSA) on the mechanical properties of as-extruded Mg–8Gd–3Y–0.5Ag–0.5Zr alloy (E alloy). Compared with the SSA treatment, the TSA treatment increased the number density of $\beta ^{\prime}$ phase. The P2%SSA and P2%TSA treatments generated the $\gamma ^{\prime}$ phase and chain-like precipitates in addition to the $\beta ^{\prime}$ phase. The contributions of these ageing treatments to the alloy strengthening can be ranked as P2%TSA > P2%SSA > TSA > SSA, because the increments in the tensile yield strength were estimated to be 199 MPa > 148 MPa > 144 MPa > 110 MPa. Different from the traditional strengthening of $\beta ^{\prime}$ phase in the E + SSA and E + TSA alloys, the composite precipitates comprising the $\beta ^{\prime}$ phase, $\gamma ^{\prime}$ phase and chain-like precipitates in the E + P2%SSA and E + P2%TSA alloys provided better combined strengthening effect. The $\beta ^{\prime}$ phase was still dominated in the strengthening effect of the composite precipitates. Owing to the higher number density of $\beta ^{\prime}$ phase in the composite precipitates, the E + P2%TSA alloy exhibited the better mechanical performance as compared with the E + P2%SSA alloy. Finally, the E + P2%TSA alloy had the ultimate tensile strength of 452 MPa, the tensile yield strength of 401 MPa and elongation to failure of 3.3%.     

铸造用CO2硬化聚乙烯醇粘结剂促硬剂的研究

研究了CO2更化聚乙烯醇粘结剂的促硬剂,是由Ca(OH)2、硅酸盐水泥及一种水硬性材料复合混制而成,原料来源广泛,价格低廉.加入促硬剂后,缩短硬化时间,大幅度提高粘结剂的粘结强度,并加入交联剂、偶联剂进一步提高粘结剂工艺强度.试验中通过正交试验优化各组分的添加比例,并对混合后型砂的可使用时间、吹制砂芯的存放性、溃散性和发气性等工艺性能进行了试验,并对性能增强机理进行简要的分析.     

R60705锆合金的热处理工艺及性能

通过力学性能测试和显微组织分析研究了R60705锆合金的热处理工艺与组织性能之间的关系。结果表明,R60705锆合金经870℃加热水冷淬火加550℃时效的热处理后具有较高的综合力学性能。组织中α相呈短条状分布,基体组织较细密。经该工艺处理后的综合力学性能满足了设备主轴的服役要求。     

Al-6.3Zn-2.8Mg-1.8Cu铸造铝合金的组织和室温力学性能

研究了Al-6.3Zn 2.8Mg-1.8Cu铸造铝合金的组织和室温力学性能.研究表明,在金属型铸造条件下,Al-6.3Zn-2.8Mg-1.8Cu合金的铸态组织为近等轴晶,相组成为α（Al）基体、枝晶间α（Al）+η（MgZn₂）共晶、晶内游离η相（MgZn₂）、少量T相（Mg₃Zn_xCu₃-_xAl₂）及少量颗粒状Al₇Cu₂Fe.固溶处理后,原铸态组织中的η（MgZn₂）相大部分溶解消失,但形成新的沿晶界分布的S相（Al₂CuMg）.实验确定了固溶态Al-6.3Zn-2.8Mg-1.8Cu合金较优的单级和双级时效工艺.与单级时效工艺相比,采用双级时效工艺处理后,抗拉强度由480 MPa增加至490 MPa,延伸率由0.2%增加至2.2%.     

气体硬化水溶性砂芯的性能研究

以电熔刚玉为骨料、氢氧化钡为粘结剂、铝粉为添加剂的型芯混合料在吹入CO_2气体后即可实现硬化。本文研究了这种型芯的硬化工艺和常温特性,并采用X射线衍射分析、失重—示差热分析等方法,结合粘结膜的扫描电镜照片,对型芯的受热物理化学变化、高温强度、水溶性等行为进行了实验研究。     

65Mn钢CCT曲线及圆锯片淬火工艺

用全自动相变测定仪测定了圆锯片常用６５Ｍｎ钢的连续冷却转为曲线，研究了不同连续冷却速度下得到的组织，为合理制订圆锯片的淬火工艺提供了依据，得到了最佳淬火工艺曲线。     

长轴表面激光淬火变形与控制

应用激光淬火强化技术控制长轴的淬火变形，分析了激光淬火变形的原因和影响因素。研究结果表明，激光淬火不仅可使长轴振摆变形量控制在很小的范围内，而且可将已变形的长轴校直到很高的精度。     

15MnVN钢的氢致硬化和氢致软化

研究了不同氢含量、应变速率条件下１５ＭｎＶＮ钢氢致硬化和氢致软化现象。试验证实，氢的存在首先造成氢致硬化，而当塑性变形开始后又导致氢致软化。这一作用受钢中氢偏聚控制，并受应变速率的诱导作用。氢的存在对钢的抗拉强度无明显影响。     

EFFECT OF PRECIPITATION HARDENING ON SERRATED FLOW CHARACTERISTICS IN AN Al－Li ALLOY

ＥＦＦＥＣＴＯＦＰＲＥＣＩＰＩＴＡＴＩＯＮＨＡＲＤＥＮＩＮＧＯＮＳＥＲＲＡＴＥＤＦＬＯＷＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＩＮＡＮＡｌ－ＬｉＡＬＬＯＹＥＦＦＥＣＴＯＦＰＲＥＣＩＰＩＴＡＴＩＯＮＨＡＲＤＥＮＩＮＧＯＮＳＥＲＲＡＴＥＤＦＬＯＷＣＨＡＲＡＣＴＥ...     

Strengthening mechanisms of a new 700 MPa hot rolled Ti-microalloyed steel produced by compact strip production

A new hot rolled titanium-microalloyed steel with yield strength of 700 MPa has been developed by CSP (compact strip production) process based on commercial weather resistant steel. EBSD results showed that the average size of its grains with high angle boundaries (>15°) was 3.3 μm. High-density dislocations and large number of nanometer particles were observed in the steel product by TEM. X-ray analysis on the electrolytically extracted phase from the steel indicated that fraction of MX phase was 0.0793 wt%, in which the particles smaller than 10 nm accounted for 33.7%. The contribution of precipitation hardening resulting from nanometer particles was calculated as approximate 158 MPa. The commercial weather resistant steel, reference steel for comparison with 450 MPa yield strength, was also prepared and investigated. It can be concluded that grain refinement is still a major strengthening mechanism in this high strength steel, but precipitation hardening of nanometer TiC precipitates is the dominant factor to increasing the yield strength in new developed steel compared with the reference steel.