V法铸造生产叉车前桥气孔与缩孔缺陷改进措施

针对V法铸造工艺代替树脂砂工艺开发叉车前桥过程产生的孔洞类缺陷问题,通过采取控制熔炼温度、浇注温度、碳当量、残镁量、砂芯烘烤时间,以及增加铁水预处理、冷铁、砂芯排气量等措施,大量减少了气孔与缩孔缺陷,降低了废品率。

挤压速度对挤压铸造铝合金制动钳工艺的影响及数值模拟

使用有限元分析软件对铸件的挤压铸造充型过程进行数值模拟,分析挤压速度对液体流动状态及充型缺陷的影响。根据铸件结构确定出最优的挤压速度。结果表明,挤压速度对液体流动的影响较明显。挤压速度应采用分段调速,第1阶段,挤压速度为100 mm/s;第2阶段,挤压速度为15 mm/s;第3阶段,挤压速度为45 mm/s。

Effect of heat treatment on microstructure and properties of semi-solid squeeze casting AZ91D

Semi-solid AZ91D magnesium alloy billets were prepared by near-liquidus heat holding.Semi-solid squeeze casting was conducted at 575,585 and 595℃,respectively,with 1 mm·s^-1 squeeze speed.The semisolid squeeze casting AZ91D samples were heat treated by T4(solution at 415℃for 24 h)and T6(solution at 415℃for 24 h+220℃for 8 h)processes,respectively.The microstructure and mechanical properties of the alloy in different states were investigated by means of OM,SEM and tensile testing machine.The results show that compared to as-cast alloy,the grain size of the semi-solid squeezed AZ91D decreased significantly,and with the increase of semi-solid squeeze temperature,the grain size of AZ91D increased.The grains of the alloy were refined by T4 treatment,and further refined by T6 treatment.T6 treatment greatly improved the tensile strength,elongation,and hardness,but did not significantly improve yield strength.After 575℃squeeze casting and T6 treatment,the ultimate tensile strength(UTS)reached 285 MPa,the elongation reached 13.36%,and the hardness also reached the maximum(106.8 HV),but the yield strength(YS)was only 180 MPa.During the process of semi-solid squeeze casting and heat treatment,the matrix grain was refined and a large number of precipitated and secondary precipitated phases of Mg17Al12 appeared.Both the average size of matrix grain and secondary precipitated phase decreased,while the volume fraction of secondary precipitated phase increased.All these resulted in high tensile strength,elongation and hardness.

Effects of SiC_(p) on microstructures of semi-solid extruded AZ91D magnesium alloys in recrystallization process

AZ91 D and 8.5 vol.%SiC_(p)/AZ91 D magnesium matrix composites were fabricated by a semi-solid extruded processing method,and treated with solution and aging heat treatment.The effects of SiC_(p)on the microstructures of the semi-solid extruded AZ91 D magnesium alloy during recrystallization were studied by observing and analyzing the microstructure evolution during extrusions and heat treatments.The results show that the addition of SiC_(p)inhibits the dynamic recrystallization of AZ91 D during the semi-solid extrusion with only 26% of the volume fraction of recrystallization.Furthermore,the addition of SiC_(p)refines the sizes of grains and second phases,and upgrades the volume fraction of second phase.After solution and aging treatment,the recrystallization continues,and the addition of SiC_(p)promotes the recrystallization and the recrystallized microstructure is much more stable.Meanwhile,the sizes of grains and second phases continue to be refined,and the volume fraction of second phases continues to increase.

叉车前桥V法铸造工艺开发

针对树脂砂铸造工艺生产叉车前桥铸件中生产效率低、成本高、环境差和铸件表面粗糙、尺寸一致性差等问题,采用V法铸造工艺替代树脂砂铸造工艺,获得了良好表面质量、尺寸精度及力学性能满足客户要求的叉车前桥铸件,同时生产效率提高、生产成本降低。

挤压铸造SiC_(p)/AZ91D镁基复合材料的组织与性能

通过585℃半固态机械搅拌+595℃近液相线保温+585℃挤压铸造,制备出SiC_(p)含量为8.5%的SiC_(p)/AZ91D镁基复合材料,再经过415℃×24h固溶处理(T4)+220℃×8h时效处理(T6)后,对其进行组织和性能检测。结果表明,挤压铸造和热处理使该镁基复合材料的组织和性能得到提高。挤压铸造后,该复合材料的组织晶粒细化成等轴晶粒,其晶界被大量SiC_(p)占据;经过固溶时效处理后,组织晶粒中析出了大量一定位向的层片状Mg_(17)Al_(12)相。经挤压铸造后复合材料的强度达到191.06MPa,伸长率为1.75%,硬度(HV)达到143.4;经过固溶时效处理后复合材料的抗拉强度达到241.26MPa,伸长率为4.22%,硬度(HV)达到152.5。

固溶时效对半固态挤压SiC/AZ91D组织与性能的影响

为了获得综合力学性能良好的镁基复合材料,采用近液相线保温法制备10μm 15%SiC/AZ91D(质量分数)半固态坯料进行半固态挤压后得到其复合材料,再经过415℃固溶处理24 h(T4)和进一步220℃时效处理8 h(T6)。结果表明:随着固溶时效的进行,晶界处的层片状和点状Mg_(17)Al_(12)相溶解,然后在晶粒中二次析出,并逐渐球化。与T6处理前的15%SiC/AZ91D复合材料相比,经T6处理后其具有良好的综合力学性能,拉伸强度、屈服强度、伸长率和硬度(HV)分别达到242 MPa、204 MPa、2.3%和1322 MPa。