通过理论分析 ,证实了预变形调整 Al- Si Cw/Al复合材料热残余应力的可行性。采用压力铸造方法制造 Al- Si Cw/Al复合材料 ,试验研究了预变形对其残余应力及拉伸性能的影响。结果表明 ,Al- Si Cw/Al复合材料经预变形处理后残余应力明显...通过理论分析 ,证实了预变形调整 Al- Si Cw/Al复合材料热残余应力的可行性。采用压力铸造方法制造 Al- Si Cw/Al复合材料 ,试验研究了预变形对其残余应力及拉伸性能的影响。结果表明 ,Al- Si Cw/Al复合材料经预变形处理后残余应力明显降低 ,力学性能得到改善。展开更多
Resin-bonded Al-SiC composite was sintered at 1100,1300,and 1500℃ in the air,the oxidation mechanism was investigated.The reaction models were also established.The oxidation resistance of the Al-SiC composite was sig...Resin-bonded Al-SiC composite was sintered at 1100,1300,and 1500℃ in the air,the oxidation mechanism was investigated.The reaction models were also established.The oxidation resistance of the Al-SiC composite was significantly enhanced with temperature increase.SiC in the exterior of the composite was partially oxidized slightly,while the transformation of metastable Al_(4)C_(3) to stable Al_(4)SiC_(4) existed in the interior.At 1100℃,Al in the interior reacted with residual C to form Al_(4)C_(3).With increasing to 1300℃,high temperature and low oxygen partial pressure lead to active oxidation of SiC,and internal gas composition transforms to Al_(2)O(g)+CO(g)+SiO(g)as the reaction proceeds.After Al_(4)C_(3) is formed,CO(g)and SiO(g)are continuously deposited on its surface,transforming to Al_(4)SiC_(4).At 1500℃,a dense layer consisting of SiC and Al_(4)SiC_(4) whiskers is formed which cuts off the diffusion channel of oxygen.The active oxidation of SiC is accelerated,enabling more gas to participate in the synthesis of Al_(4)SiC_(4),eventually forming hexagonal lamellar Al_(4)SiC_(4) with mutual accumulation between SiC particles.Introducing Al enhances the oxidation resistance of SiC.In addition,the in situ generated non-oxide is uniformly dispersed on a micro-scale and bonds SiC stably.展开更多
Stir casting method was used to produce conventional metal matrix composites (MMC) with fairly homogenous dispersion of reinforcement material. Commercial pure aluminum and silicon carbide particles (50 μm) were sele...Stir casting method was used to produce conventional metal matrix composites (MMC) with fairly homogenous dispersion of reinforcement material. Commercial pure aluminum and silicon carbide particles (50 μm) were selected as matrix and reinforcement materials respectively. The matrix was first completely melt and kept constant at 750°C. Then SiC powder preheated to 800°C was added during stirring action. No wetting agents were used. The melt mixture was poured into a metallic mold. The composite contents were adjusted to contain 5% and 10% SiC. The as-cast composites were processed by Equal Channel Angular Pressing (ECAP) route A. The microstructure and mechanical properties were studied. Results indicated that as cast AlSiC composites can be successfully fabricated via a cheap conventional stir casting method, giving fairly dispersed SiC particle distribution and having low porosity levels 3.6%. The mechanical properties have improved compared to as cast composites. ECAP technique has greatly reduced SiC particles from 50 to 3 μm. After the first ECAP pass, yield strength has almost twice its value in the as cast composites. The maximum yield of 245 MPa obtained after 8 passes is almost four times the corresponding values of the as cast MMC composites. Hardness has also increased to 1.5 times its value in the as cast composites after one ECAP pass. The maximum hardness of 71 HRB obtained after 8 passes, which is almost 3.5 times the corresponding values of the as cast MMC composites.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFB3701400).
文摘Resin-bonded Al-SiC composite was sintered at 1100,1300,and 1500℃ in the air,the oxidation mechanism was investigated.The reaction models were also established.The oxidation resistance of the Al-SiC composite was significantly enhanced with temperature increase.SiC in the exterior of the composite was partially oxidized slightly,while the transformation of metastable Al_(4)C_(3) to stable Al_(4)SiC_(4) existed in the interior.At 1100℃,Al in the interior reacted with residual C to form Al_(4)C_(3).With increasing to 1300℃,high temperature and low oxygen partial pressure lead to active oxidation of SiC,and internal gas composition transforms to Al_(2)O(g)+CO(g)+SiO(g)as the reaction proceeds.After Al_(4)C_(3) is formed,CO(g)and SiO(g)are continuously deposited on its surface,transforming to Al_(4)SiC_(4).At 1500℃,a dense layer consisting of SiC and Al_(4)SiC_(4) whiskers is formed which cuts off the diffusion channel of oxygen.The active oxidation of SiC is accelerated,enabling more gas to participate in the synthesis of Al_(4)SiC_(4),eventually forming hexagonal lamellar Al_(4)SiC_(4) with mutual accumulation between SiC particles.Introducing Al enhances the oxidation resistance of SiC.In addition,the in situ generated non-oxide is uniformly dispersed on a micro-scale and bonds SiC stably.
文摘Stir casting method was used to produce conventional metal matrix composites (MMC) with fairly homogenous dispersion of reinforcement material. Commercial pure aluminum and silicon carbide particles (50 μm) were selected as matrix and reinforcement materials respectively. The matrix was first completely melt and kept constant at 750°C. Then SiC powder preheated to 800°C was added during stirring action. No wetting agents were used. The melt mixture was poured into a metallic mold. The composite contents were adjusted to contain 5% and 10% SiC. The as-cast composites were processed by Equal Channel Angular Pressing (ECAP) route A. The microstructure and mechanical properties were studied. Results indicated that as cast AlSiC composites can be successfully fabricated via a cheap conventional stir casting method, giving fairly dispersed SiC particle distribution and having low porosity levels 3.6%. The mechanical properties have improved compared to as cast composites. ECAP technique has greatly reduced SiC particles from 50 to 3 μm. After the first ECAP pass, yield strength has almost twice its value in the as cast composites. The maximum yield of 245 MPa obtained after 8 passes is almost four times the corresponding values of the as cast MMC composites. Hardness has also increased to 1.5 times its value in the as cast composites after one ECAP pass. The maximum hardness of 71 HRB obtained after 8 passes, which is almost 3.5 times the corresponding values of the as cast MMC composites.
